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2018 Spring Meeting



Solid state ionics: advanced functional materials for solid state devices

Defects, surfaces and interfaces play a major role in the transport and catalytic properties of functional materials. This symposium will focus on strategies to understand and control the functional properties of ionic and mixed conducting materials, with a view toward their application in solid state devices, such as batteries, solid oxide cells, gas sensors and memristive devices.


The functional properties of solid state ionic devices, such as batteries, solid oxide cells (SOCs), gas sensors and memristive devices, strongly depend on mass and charge transport occurring in the nanoscale. These processes are related not only to the bulk material itself and the surrounding conditions, such as temperature, oxygen partial pressure or applied electrical field, but also on the presence of local heterogeneities, mainly point defects, grain boundaries, surfaces, disolcations and interfaces. It is increasingly common for researchers to seek novel and optimized functionalities in advanced materials through the creation of “natural” or artificial interfaces (e.g. bilayers, multilayers), controlled grain boundaries (e.g. thin films with high densities of defects) and optimized surfaces (e.g. preventing segregation or enhancing surface kinetics).

The goal of this symposium is to move from the fundamentals – the physics and chemistry of defects in solid materials – to technological applications, thus linking theory, simulations, functional properties and real applications. This symposium will provide a forum for extensive discussion and exchange of information among researchers exploring defect management in functional oxides in different contexts and diverse applications. This will include state-of-the art methods for structural and chemical characterization such as high resolution transmission electron microscopy, synchrotron-based spectroscopy and diffractometry, scanning probe microscopy and atom probe tomography, combined in many cases with modeling and simulation methodologies such as density functional theory and molecular dynamics. In addition, new methodologies for engineering ionic transport in functional materials will also be one of the main topics under discussion, with special emphasis in high throughput screening, heterostructuring, doping and strain. Electrolysis, switching phenomena, photocatalysis, gas sensing, and thin film based solid state devices for energy and informatics (batteries, solid oxide fuel cells, memristors) will be some of the main applications and devices to be discussed.

Hot topics to be covered by the symposium:

Papers are solicited on (but not limited to) the following topics:

  • Defect control in functional oxide interfaces, catalytic surfaces and memristive devices
  • Nanoionics: mass and charge transport in the nanoscale
  • Grain boundary transport
  • Mass transport in bulk materials for solid state devices
  • Methodologies for engineering ionic transport in functional materials: high throughput screening, heterostructuring, doping, strain, etc
  • Electrolysis of CO2 and H2O
  • Switching phenomena
  • Photocatalysis
  • Thin film based solid state devices for energy applications: batteries, solid oxide fuel cells, etc.
  • Gas sensors and memristive devices

Confirmed list of invited speakers and tentative title of the presentation:

  • Jürgen Fleig, TU Wien, Austria, “Interfacial phenomena in multifunctional heterostructures”
  • Roger A. De Souza, Aachen University, Germany, “Grain boundary characterization and modeling”
  • David Diercks, Colorado School of Mines, US, “Atom probe of grain boundaries”
  • John Paul Strachan, HP labs, CA-San Jose, USA, “Revealing the origin of switching and failure mechanisms in memristive devices by spectromicroscopy”
  • Susanne Hoffmann-Eifert, FZ-Juelich, Germany, “The role of interface reactions in memristive device heterostructures”
  • Nini Pryds, DTU, Denmark, “High mobility oxide heterostructures for nanoelectronics”
  • William Chueh, Standford, USA, “”CO2 / H2O electrolysis”
  • Jennifer Rupp, MIT, USA, “Solar-to-Fuel Conversion Reactor Materials"
  • Peter Bruce, Oxford, UK, “Oxygen redox cathodes for Li-ion batteries”
  • Eugene Kotomin, Max-Planck Institute, Stuttgart, Germany, “Ab-initio modelling of oxygen vacancies in perovskites”
  • Jose Santiso, ICN2, Barcelona, Spain, “Misfit dislocations  in complex oxide epitaxial thin films”
  • Igor Lubomirsky, Weizmann Institute, Israel, “Electromechanic and inelastic effects in oxygen deficient ceramics”
  • Yan Chen, South China University of Technology, China, “Electrochemical reaction processes near the surface and interface of oxide materials”
  • Ainara Aguadero, Imperial College London, UK, “Electrocatalyst for oxygen evolution and reduction reactions”
  • Christian Jooss, University of Göttingen, Germany, “Defect control at catalytic surfaces

Tentative list of scientific committee members:

  • J. A. Kilner, Imperial College, London, UK
  • J. Maier, Max Planck Institute for Solid State Research, Germany
  • J. T. S. Irvine University of St Andrews, UK
  • B. Scrosati, University of Rome La Sapienza, Italy
  • S. Passerini, Helmholtz-Institut Ulm, Germany
  • T. Norby, University of Oslo, Norway
  • H. L. Tuller, Massachusetts Institute of Technology, Cambridge, USA
  • Z. Shao, Nanjing University of Technology, China
  • M. Mogensen, Technical University of Denmark, Denmark
  • B. Yildiz, Massachusetts Institute of Technology, Cambridge, USA
  • S. Barnett, Northwestern University, USA
  • G. Dezanneau, CNRS, France
  • R. O’Hayre, Colorado School of Mines, USA
  • M. Varela, Universidad Complutense de Madrid, Spain
  • T. Ishihara, Kyushu University, Fukuoka, Japan


Selected papers will be published in a special issue of the journal Solid State Ionics (Elsevier Ltd.)

Poster awards:


The journal Solid State Ionics (Elsevier Ltd.) has agreed to sponsor the poster awards.
3 poster prizes per session (2) will be given:
- 1st prize: 250 euros,
- 2nd prize: 150 euros,
- 3rd prize 100 euros.

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Interface & Surface Phenomena (I) : David S. Mebane
Authors : Roger A. De Souza
Affiliations : Institute of Physical Chemistry, RWTH Aachen University, Germany

Resume : There is renewed interest in the atomistic structure and transport properties of dislocations in the perovskite oxide SrTiO3, driven by the material's possible application in devices for all-oxide electronics and for resistive switching. Low-angle grain boundaries constitute elegant systems for studying dislocations and their properties. In my talk, I will demonstrate how atomistic simulations can be used to obtain a deeper understanding of these topics. In the first part I will describe our efforts towards predicting the structure, type, arrangement and alignment of edge dislocations at a given tilt low-angle grain boundary in SrTiO3. Subsequently, I will briefly discuss the thermodynamics of space-charge formation at extended defects. Finally, I will focus on the effect of electric fields on grain-boundary properties.

Authors : F. Gunkel, M. Rose, J. Börgers, R. Heinen, S. Hoffmann-Eifert, R. Waser
Affiliations : IWE2 and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany; PGI7, Forschungszentrum Jülich GmbH, Jülich, Germany;

Resume : Low-dimensional electron transport along complex oxide heterointerfaces and the emergence of magnetism in these nominally non-magnetic systems has attracted enormous attention in recent years. In epitaxial systems, the formation of these 2-dimensional electron gases is attributed to electronic charge transfer triggered by a built-in electric field, which at the same time implies a specific ionic defect structure at the interface. Here, we discuss implications of defect formation and scattering for the low-dimensional electron transport and magnetism in these systems. As we show, low temperature resistance characteristics, electron mobility, as well as magnetic signature of the electron gas can be systematically controlled by thermodynamic means, i.e., the control of the ionic-electronic defect structure. The systematic relation between defect structure and transport phenomena will be demonstrated using different examples including the appearance of a Kondo-like resistance upturns, anomalous Hall effect, quantum interference phenomena (weak-anti-localization), and positive-to-negative magneto resistance transitions in defective heterostructures.

Defects & Transport Phenomena (I) : Eugene Kotomin and Igor Lubomirsky
Authors : Daniel Mierwaldt, Thilo Kramer, Vladimir Roddatis , Marcel Risch, Christian Jooss
Affiliations : Inst. of Materials Physics, Univ. of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany

Resume : In-situ studies of electrochemical processes at interfaces are of high interest since they offer the opportunity to study the involved defect chemical processes in operando. We present two main examples, where the dynamics of anion as well as cation vacancies during redox processes can be directly visualized with high spatial and energy resolution: (i) An Environmental Transmission Electron Microscopy (ETEM) and X-ray absorption spectroscopy (XAS) study of O2 evolution catalysis during H2O splitting in various doped manganite perovskite and Ruddlesden-Popper phases. These systems offer the opportunity for fundamental studies of factors such as valence and covalence, controlling the active site, surface structure and defect chemistry in water splitting and oxygen evolution [1-4]. (ii) An ETEM study of electrochemical processes at perovskite ? noble metal interfaces involved in resistive switching under electric pulses. Here, an insulator metal transition is induced by oxygen vacancies close to the interface [5,6]. Careful studies of beam induced effects in in situ ETEM and XAS studies are discussed, in order to give support the significance of the in situ observations for real world electro-chemistry. References [1] S. Raabe, D. Mierwaldt, J. Ciston, M. Uijttewaal, H. Stein, J. Hoffmann, Y. Zhu, P. Blöchl, and Ch. Jooss, Adv. Funct. Mater. 22 (2012) 3378. [2] S. Mildner M. Beleggia, D. Mierwaldt Th. W. Hansen, J. B. Wagner, S. Yazdi, T. Kasama, J. Ciston, Y. Zhu, and Ch. Jooss, J. Phys. Chem. C, 119 (2015) 5301. [3] D. Mierwaldt, S. Mildner, R. Arrigo, A. Knop-Gericke, E. Franke, A. Blumenstein, J. Hoffmann, C. Jooss, Catalysts 4 (2014) 129. [4] D Mierwaldt, V Roddatis, M Risch, J Scholz, J Geppert, M E Abrishami, and Ch Jooss, Adv. Sustainable Syst. 2017, 1, 1700109. [5] T Kramer, D Mierwaldt, M Scherff, M Kanbach, and Ch Jooss, Ultramicroscopy 184 (2017) 61. [6] T Kramer, M Scherff, D Mierwaldt, J Hoffmann and Ch Jooss, Appl. Phys. Lett. 110 (2017) 243502.

Authors : Gee Yeong Kim1*, Alessandro Senocrate1,2, Tae-Youl Yang1, Giuliano Gregori1, Michael Grätzel1,2 and Joachim Maier1,2
Affiliations : 1Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany 2Laboratory of Photonics and Interfaces, Ecole polytechnique Fédérale (EPFL) de Lausanne, Lausanne CH-1015, Switzerland

Resume : Methylammonium lead halide perovskite (MAPbI3) solar cells have become a key light harvesting element in the field of energy conversion showing excitingly high conversion efficiencies. To account for key features responsible for such performances, not only electronic, but also ionic transport properties need to be considered. In addition, ion transport is fundamental for degradation kinetics of most materials. To measure and separate both transport contributions not only in the dark, but also under illumination, we performed electrochemical studies by using various techniques such as transference number measurements, Faradaic experiments, permeation studies, stoichiometric variations, Hall effect experiments and the use of blocking electrodes. We provide, for the first time, clear evidence of an enhancement of the ionic conductivity by two orders of magnitude in MAPbI3 by light illumination. We discuss the results in the context of defect-chemical models and transport experiments developed in our group [1, 2]. Based on these experimental results, we also present a mechanistic explanation for the photo-enhanced ion conduction [3]. We also show that this surprising result gives rise to a novel and very general decomposition path for metal halide perovskites. References [1] T. -Y. Yang, G. Gregori, N. Pellet, M. Grätzel, J. Maier, Angew. Chemie Int. Ed. (2015), 54, 7905–7910. [2] A. Senocrate, I. Moudrakovski, G. Y. Kim, T. –Y. Yang, G. Gregori, M. Grätzel, J. Maier, Angew. Chemie Int. Ed. (2017), 56, 1-6. [3] G. Y. Kim, A. Senocrate, T. –Y. Yang, G. Gregori, M. Grätzel, J. Maier, submitted (2017).

Authors : Shiny Mathew, David J. Payne, Robert G. Palgrave
Affiliations : Shiny Mathew, EPSRC Centre for Doctoral Training in Advanced Characterisation of Materials, University College London David J. Payne, Imperial College London Robert G. Palgrave, University College London

Resume : The use of doped TiO2 as a photocatalyst in water splitting for hydrogen production continues to demonstrate significant potential in renewable energy technology devices. We characterised the behaviour, nature and spatial location of non-metal ion dopants in the TiO2 matrix. To create a stable dopant distribution profile that can be probed in the 3D space, single crystal substrate forms of TiO2 were used. We investigated the diffusion of nitrogen, sulphur, carbon and boron dopants into TiO2 (110), (100), (001) substrates using a novel high temperature method. The former three dopants were found to be in interstitial and substitutional sites with a concentration gradient into the bulk, as measured by the Thermoscientific (K-alpha & Theta probe) X-ray photoelectron spectroscopy. We also report the growth of a TiBO3 phase (at least 20nm thick) in multiple orientations, different to that of the TiO2 (110) substrate. XRD has confirmed a film-like layer of TiBO3 on the TiO2 surface whilst Raman spectroscopy has shown potential uniform growth of TiBO3 on the TiO2 (100) and (001) surfaces but not on the TiO2 (110) surface. Reciprocal space maps revealed the orientation of the TiBO3 layer. Whilst the ability to grow thick films of TiBO3 is crucial for the advancement of facile film growth technology, fundamental insight into dopant diffusion gradients is significant for the investigation of structure-function relationship, essential for designing materials with optimised photoactivity.

Authors : Yoshitaka Aoki, Chiharu Kura, Chunyu Zhu, Hiroki Habazaki
Affiliations : Faculty of engineering, Hokkaido university

Resume : In a sustainable society, the use of rare elements should be minimized by their replacement with more abundant ones. For instance, palladium is a rare metal extensively used in hydrogen separation membranes to produce pure H2 gas from the gas mixtures generated by water electrolysis, methane steam reforming, partial oxidation of natural gas and so on. Indeed, the increasing demand for pure hydrogen as a clean and efficient energy source has drawn much academic and industrial interest to the development of non-Pd-based alternatives. Since hydrogen dissolved in the metal matrix aids its deformation, metals exhibiting high hydrogen solubility are subject to increased embrittlement. Thus, materials scientists are faced with the challenge of designing hydrogen separation membranes that do not rely on hydrogen solubility in a metal matrix. Mixed proton?electron conductors are promising alternatives to dense separation membranes, featuring ambipolar diffusion of H+ and e? . Although perovskite-type BaM1?xM?xO3?? (M = Ce, Zr; M? = Y, Yb and so on) proton-conducting ceramics have been extensively studied as potential mixed proton?electron conductors, they require operation at elevated temperatures (T > 600 °C) due to high migration activation energies (50?60 kJ mol?1) attributed to trapping by negatively charged aliovalent dopants or defect induced structural distortions. Herein, we report we report room-temperature hydrogen permeability of titanium nitrides (widely used as tough and inert coating materials) enabled by mixed hydride ion?electron conductivity. Combined spectroscopic, permeability and microgravimetric measurements reveal that nanocrystalline TiNx membranes feature enhanced grain-boundary diffusion of hydride anions associated with interfacial Ti cations on nanograins, i.e. hydridic Ti?H terminal groups on the hydrogenated grain surface. Since the corresponding activation energies are very low (< 10 kJ mol?1), these membranes yield a considerably higher room-temperature hydrogen flux than Pd membranes of equivalent thickness. DFT calculations clarify the hopping dynamics of hydride ion and the factors for the significantly-reduced diffusion barriers in the grain boundary region. Overall, the current study establishes general guidelines for developing hydride ion transport membranes.

Authors : Sebastián Murcia-López,1 Qin Shi,1,2 Pengyi Tang,1 Zhaoyong Bian,3 Hui Wang,2 Joan Ramón Morante,1 Teresa Andreu1
Affiliations : 1. Department of Advanced Materials for Energy, Catalonia Institute for Energy Research (IREC), Spain. 2. College of Environmental Science and Engineering, Beijing Forestry University, China. 3. College of Water Sciences, Beijing Normal University, China

Resume : Among other metal oxides, monoclinic bismuth vanadate (BiVO4) is one of the most promising photoanode materials for photoelectrochemical (PEC) water splitting, considering its relatively low band gap value. In order to further improve its properties, tungsten doping has been widely considered a promising strategy for alleviating some of its intrinsic limitations: excessive surface recombination and poor charge transport. In general terms, the PEC enhancement at low W content has been mostly attributed to an increase in the charge donor density, as V sites are occupied by W acting as electron donor. In this work, in-deep electrochemical, photoelectrochemical and impedance spectroscopy measurements on W-BiVO4 electrodes fabricated by electrospinning with different W-contents have been carried out for elucidating the role of W on the formation of surface states (SS). This way, an optimum ratio of surface states (NSS) and charge donor densities (ND) is found for the 2% doping, which provides high conductivity and reaction sites. Additionally, two types of SS are proposed: reaction sites (i-SS) and recombination sites (r-SS), which are formed with a closed dependence on the W-doping content, tuning the electron trapping process and the overall PEC performance. This work gives a further understanding on the enhancement of PEC performance caused by W doping in the field of charge transfer at semiconductor/electrolyte interface.

Authors : Alessandro Senocrate 1,2, Tae-Youl Yang 1, Igor Moudrakovski 1, Gee Yeong Kim 1, Giuliano Gregori 1, Michael Grätzel 1,2, Joachim Maier 1
Affiliations : 1 Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany; 2 École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Resume : In recent years, hybrid halide perovskites attracted much attention for their potential use as light-harvesters in solar cells, due to their high absorption coefficients and long electron-hole diffusion lengths[1-2] that yield devices with photo-conversion efficiencies exceeding 22%. However such devices, under operation, show important polarization phenomena[3,4] (that can affect bulk charge transport and interfacial charge transfer), caused by the substantial ionic conductivity of the halide perovskite.[5] In this contribution, we study the nature of this ionic conductivity by investigating methylammonium lead iodide, the archetypal halide perovskite, by means of d.c. galvanostatic polarization, voltage measurements in electrochemical cells and NMR spectroscopy.[6] We observe a significant ionic conductivity under equilibrium conditions, with I- ions as the majority migrating species. By measuring conductivity as a function of stoichiometry and dopant concentration, we identify the dominant electronic and ionic charge carriers as electron holes and iodine vacancies. The results are discussed alongside a simple defect chemical model. REFERENCES: [1] C. C. Stoumpos et al., Inorg. Chem. 2013, 52, 9019. [2] D. Shi et al., Science 2015, 347, 519. [3] H. J. Snaith et al., J. Phys. Chem. Lett. 2014, 5, 1511. [4] Z. Xiao et al., Nat. Mater. 2015, 14, 193. [5] T.-Y. Yang et al., Angew. Chemie 2015, 54, 7905. [6] A. Senocrate et al., Angew. Chemie 2017, 56, 7755.

Solid State Electronic Devices (I): Resistive Switching : Regina Dittmann and Nini Pryds
Authors : John Paul Strachan, Suhas Kumar, Miao Hu, Catherine Graves, R. Stanley Williams
Affiliations : Hewlett Packard Labs, HPE

Resume : I describe our work spanning atomic understanding and engineering of memristors, integration with CMOS circuits, and experimental demonstrations of computing accelerators for key applications. We performed soft x-ray spectro-microscopy measurements on working memristor devices using an in-operando time-multiplexed technique. During cycling, we observed the formation of oxygen-rich and oxygen-deficient regions with a radial geometry consistent with elevated core temperatures driving Fick diffusion and thermophoresis. Under high voltage stress operations, these regions continued to evolve and ultimately contributed to device failure. Using similar techniques, we characterized neuronic memristive devices based on niobium oxide. Complementing the physical characterization, interesting electrical dynamics was observed that we described as positive feedback coupled to thermal fluctuations. Tunable chaotic behavior was observed and utilized for the construction of a computing system to solve optimization problems such as the traveling salesmen problem. I will describe how the above novel device properties have been utilized by my team to develop novel computing architectures to accelerate many applications in image and signal processing, neural networks, and scientific computations. Significant performance gains and energy reductions over purely digital systems are forecasted.

Authors : O. Blázquez,1,2 J. L. Frieiro,1,2 J. López-Vidrier,3 L. López,1,2,4 C. Clement,5 S. Estradé,1,2 X. Portier,5 S. Hernández,1,2 F. Peiró,1,2 C. Labbé,5 B. Garrido,1,2
Affiliations : 1MIND, Department of Engineering: Electronics, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona (Spain); 2Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Av. Joan XXIII S/N, E-08028 Barcelona (Spain); 3Laboratory for Nanotechnology, Dept. of Microsystems Engineering (IMTEK), University of Freiburg, Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 103, D?79110 Freiburg (Germany); 4TEM-MAT Unit, Scientific and Technological Centers, Universitat de Barcelona. C/Lluís Solé i Sabarís 1, E-08028 Barcelona (Spain); 5CIMAP UMR 6252 CEA-CNRS-ENSICAEN, UNICAEN, 6 boulevard Maréchal Juin, F-14050, Caen Cedex 4 (France);

Resume : Nowadays, memristive materials are providing a solution to the fast scaling in electronics in the form of resistive electronic memories (ReRAM). The alternate creation and destruction of conductive nanofilaments (CNFs) due to ionic movement, produces the switching between a high resistant state (HRS) and a low resistant state (LRS), under certain applied voltage. ZnO, widely studied for gas sensing and as transparent conductive oxide (TCO) in photovoltaics, has become a potential candidate for making transparent ReRAM devices. Here, we report on the memristive properties of ITO/ZnO/p-Si devices deposited via sputtering. After the electroforming process, the devices can switch from the HRS to the LRS with a difference of more than 5 orders of magnitude in current, by intensity-voltage cycles at low voltages (±1 V) and free compliance, demonstrating endurance beyond 100 cycles. The charge transport mechanisms have been studied in the three different conduction states (pre-electroforming, at LRS and HRS): whereas LRS presents space-charge-limited current, at pre-electroforming and HRS states trap-assisted tunneling mechanism dominates conduction, reaching the Fowler-Nordheim injection regime at larger electric fields. The proposed transport model is correlated to the structural creation and destruction of CNFs via valence change mechanism.

Authors : Jonas Deuermeier(1)*, Asal Kiazadeh(1), Hongjun Liu(2), Laetitia Rapenne(2), David Muñoz-Rojas(2), Andreas Klein(3), Rodrigo Martins(1), and Elvira Fortunato(1)
Affiliations : (1) i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa and CEMOP/UNINOVA, Campus de Caparica, 2829-516 Caparica, Portugal; (2) Université Grenoble Alpes, CNRS, Grenoble INP, LMGP, Grenoble F-38000, France; (3) Department of Materials and Earth Sciences, Technische Universität Darmstadt, Otto-Berndt-Straße 2, D-64287, Germany

Resume : Copper oxide Cu2O is easily oxidized or reduced. This introduces secondary phases of CuO or metallic copper in the material and creates additional functional interfaces. Highly conductive CuO is found in the grain boundaries of Cu2O. Metallic copper is found at the interface between Cu2O and Al2O3 deposited by atomic layer deposition. In order to have a precise characterization of such secondary phases, material analysis relies on in situ X-ray photoelectron spectroscopy, high resolution automated phase mapping by transmission electron microscopy and conductive atomic force microscopy. The secondary phases in copper oxide are responsible for poor performance of devices like thin-film transistors and solar cells. However, these defects are the basis of the resistive switching mechanism in a Cu2O/Al2O3 bilayer memory, which is discussed in this contribution. The bipolar resistive switching properties can be programmed in a multilevel cell (MLC) operation by applying different current compliance (10 µA, 50 µA and 500 µA) in the set process and by using different reset voltages. The data is retained longer than 5000 s, but the cycle-to-cycle uniformity is different for each conductance state. This correlates to the size and nature of the filament in the copper oxide layer and the way it interacts with the highly conductive grain boundaries.

Authors : F.V.E. Hensling, C. Bäumer, N. Raab, R. Dittmann
Affiliations : PGI-7 Forschungszentrum Jülich

Resume : A central challenge in today?s scientific community is the need for faster and smaller non-volatile memory devices. A potential candidate for achieving such devices is the mechanism of resistive switching, which is intensely researched for the filamentary switching SrTiO3 (STO). Yet there are still plenty of open questions regarding the in depth understanding of the switching mechanism of STO. In the past we have shown that epitaxially grown STO with an excess of Sr shows an increased memory window and an improved retention of the low resistive state (LRS) [1]. In order to understand the improved switching behavior of Sr-rich STO thin film devices, we investigated the Sr-excess compensation during PLD growth. We considered two extreme cases of Sr-excess accommodation: the formation of stacking faults within and the segregation of SrO on top of the thin film. We tried to artificially engineer these two by intentionally depositing additional SrO. We observed that thin film stacks with SrO at the bottom interface result in forming free devices. Additional SrO to the top interface, however, results in an improved memory window and retention. We attribute the improved retention of the LRS to the impeded reoxidation of the conducting filament [2]. These results provide a pathway to a design of resistive switching devices with the possibility of prepositioning switching filaments. [1] Raab et al. AIP Adv. (2015) [2] Baeumer et al. Nat. Comm. (2015)

Authors : A. Palau 1, J.C. Gonzalez-Rosillo 1, R. Ortega 1-2, M. Coll 1, B. Arndt 3, R. Dittmann 3, I. Maggio-Aprile 4, J. Suñé 2, N. Mestres 1, X. Obradors 1, T. Puig 1
Affiliations : 1 Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, Bellaterra, Spain; 2 Departament d'Enginyeria Electrònica, Universitat Autònoma de Barcelona, Bellaterra, Spain; 3 Institute of Solid State Research, Forschungszentrum Juelich, Germany; 4 Department of Condensed Matter Physics, Univ. of Geneva, Switzerland

Resume : Nonvolatile memories based on the Resistive Switching (RS) effect, where different reversible resistance states can be induced upon application of an electric field, appear as a new emerging technology to overcome the limitations in Flash and RAM memories. This phenomenon has been observed in many oxide systems, in particular in perovskite oxides, which show outstanding properties giving rise to exotic physical phenomena due to the strong electronic correlation, such as metal-insulator transitions (MIT). This is the case of the metallic perovskite La1-xSrxMnO3 and YBa2Cu3O7 family compounds, which are able to display Volume RS effects induced by the MIT and therefore, small changes in carrier concentration can induce huge resistance changes [1]. The mechanism underlying this phenomenon is still unclear although oxygen vacancies mobility plays a crucial role. In this presentation, we will discuss our studies on bipolar resistive switching of the mentioned perovskite oxides. Switching characteristics have been evaluated by C-SPM and I(V) curves with metal electrodes. Scanning tunneling microscopy and spectroscopy (STM/S), transport and resistive measurements were performed to gain insight into the local density of states of the material for different resistance states. We will show that oxygen mobility at the interfaces and within the film have a significant impact on the resistive switching properties of metallic perovskites. [1] Gonzalez-Rosillo et al, J. Electroc. 1-4, 2017

Authors : Wei-Chih Hou1, Yu-Jui Wu2, Bo-Ting Lin2, Miin-Jang Chen2, and Jiun-Yun Li1, 3, 4
Affiliations : 1 Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan; 2 Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan; 3 Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 4 National Nano Device Laboratories, National Applied Research Laboratories, Hsinchu, Taiwan

Resume : Resistive random access memory (RRAM) is a promising candidate for the next-generation low power memory device applications. For conventional oxide-based RRAM devices, the On/Off ratio is 10^2 ~ 10^3. In this work, we present an extremely high On/Off ratio of 10^8 in ferroelectric-based RRAM devices. Instead of using CMOS-incompatible dielectrics for RRAM devices such as TiO2 or SrTiO3, we used atomic layer deposition (ALD) to deposit ferroelectric-Hf0.5Zr0.5O2 (f-HZO) and ZrO2 (f-ZrO2) thin films as the active material in the RRAM devices. Pt is the bottom contact and deposited on a Si substrate followed by the deposition of ferroelectric films with Ni or Pt as the top contact. An extremely high On/Off ratio of 10^8 was achieved in both HZO and f-ZrO2 RRAM devices in the beginning phase and dropped to 106 after an operation of 500 cycles of 500-?s pulses for the endurance test. By comparing to non-ferroelectric ZrO2 RRAM devices of the On/Off ratio of 10^4, we think the residual dipoles in the ferroelectric layers would enhance the filament effects and accounts for the high On/Off ratios for ferroelectric-based RRAMs. Furthermore, we found that in O2 or forming gas (5%H2/95%N2) annealing ambience, the endurance becomes worse compared to N2 annealing, which might be related to the interaction of the oxide vacancies and reactive gases.

Solid State Energy Devices (I): Batteries : Alex Morata
Authors : X. Gao,b Y. Chen,b C. Holc,b A. Pateman, b P. G. Bruce,b L.R. Johnsona
Affiliations : a) School of Chemistry and GSK Carbon Neutral Laboratory for Sustainable Chemistry, University of Nottingham, Jubilee Campus, Nottingham NG7 2TU, UK b) Departments of Materials and Chemistry, University of Oxford, Oxford, UK.

Resume : Interest in the rechargeable Li-O2 battery is driven by its high theoretical specific energy (3500 Whkg-1).1-2 However, a number of challenges face the realization of practical devices.3-10 Overcoming these challenges requires an understanding of the reactions and processes in the cell, especially at the electrodes. Our focus has been on the reaction at the positive electrode: O2 + 2 e- + 2 Li+ = Li2O2 This simple reaction belies the complexity of the problems during charge and discharge. Li2O2, is an insulating solid, if it grows on the electrode surface it can only do so to a thickness of approx. 6 to 7 nm. The resulting passivation leads to low rates and low capacities.11 If Li2O2 grows from solution, passivation is avoided, leading to high rates and capacities.12 The solvent donor number is an important factor in controlling which pathway, surface film or solution growth, occurs. Low donor number ethers promote surface films while high donor numbers result in solution growth. Unfortunately, high donor number solvents are more susceptible to decomposition by the reactive O2- nucleophile (the intermediate in the O2/Li2O2 reaction is LiO2).13 We show that using redox mediator molecules to shuttle electrons between the electrode surface and solution, Li2O2 can be formed and decomposed in solution even in low donor number solvent like ethers. As a result, rates and capacities of several mA and mAh cm-2 respectively are observed. The impact of the mediators on solvent and electrode stability will be discussed in the context of the mechanism of Li2O2 formation and decomposition. Ultimately, the Li-O2 cell must operate in air. The effect of H2O in the gas stream and hence in the electrolyte solution on the mechanism of O2/Li2O2 and the effect on cell performance are important. The influence of H2O on the O2 reduction mechanism will be considered.

Authors : Cao Guan1*, John Wang1
Affiliations : 1Department of Materials Science and Engineering, National University of Singapore, 117574 Singapore

Resume : Highly active and durable air cathode with bifunctionality to catalyze both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required but challenging for rechargeable metal-air batteries. In this work, we report a bifunctional oxygen catalyst of hollow Co3O4 nanospheres embedded nitrogen-doped carbon nanowall arrays on flexible carbon cloth (NC-Co3O4/CC), which is facilely derived from a metal-organic framework (MOF) precursor. Unique nanoscale Kirkendall effect promoted the formation of irregular hollow Co3O4 nanospheres with plenty of nanograins and rich edges/corner reaction sites, which enables promising catalytic properties toward both OER and ORR. More importantly, the integrated NC-Co3O4/CC as an additive-free air-cathode for flexible all-solid-state Zinc-air batteries is demonstrated, which presents high open circuit potential (1.44 V), high capacity (387.2 mAh g-1), high volume capacity of 25.6 mAh cm-3, excellent cycling stability and mechanical flexibility (maintaining stable charge-discharge platform after been folded several times), outperforming the noble-metal based Zinc-air batteries.

Authors : Stefan ADAMS
Affiliations : Department of Materials Science and Engineering, National University of Singapore

Resume : Sulfide-based solid Na-ion electrolytes are crucial to enable room-temperature all-solid-state Na-ion batteries for large-scale energy storage. Compared to the wide range of Li-conductors only few fast Na-ion conducting sulfides have been identified. Among these, doped NaxMS4 (M=P,As,Sn,?) yields interesting conductivities in the range of 0.1-1 mS/cm. We demonstrate an all-solid state Na-ion full cell, that can be operated at 2C rate both at ambient and elevated temperatures.[1] The success of LGPS-type Li conductors inspired the search for analogous Na10MPS12 (M=Ge,Sn,?), but for the phases that have so far been synthesized, the experimental conductivity remained clearly below earlier predictions from high temperature ab initio molecular dynamics (MD) simulations. Here we explain based on empirical MD simulations, how cation ordering within the pathways of the LGPS-analogues significantly restricts Na-ion mobility. Our recent realisation of anion-ordered Na11Sn2PX12 [2] (X=S,Se) in space group I41/acd with a conductivity of 3-4 mScm-1, along with the parallel report on Na11Sn2SbS12 now opens up a way for all-solid state batteries with competitive power performance. Bond-valence based simulations reveal the role of vacancies in the ion transport mechanism of this new class of superionic Na conductors. [1] R. Prasada Rao et al., J. Mater. Chem. A, 2017, 5, 3377-3388. [2] M. Duchardt et al., Angew. Chem. Int. Ed., 2018, in press, doi:10.1002/anie.201712769

Poster Session 1 : Albert Tarancón
Authors : Zhipeng Gao1, Xianlin Dong2, Hongliang He1, Bin Chen3, Genshui Wang2
Affiliations : 1National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China 2CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China 3Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China

Resume : Ferroelectric materials are characterized by their non-centro symmetrical structure and the switchable polarizations. When the structure is changing under compression, the polarization would be disappear or re-orientated, inducing a drastic change of the surface charge, which is associated with the energy transition. This phenomenon have very wide applications in energy and military industries, such as nuclear fusion trigger, energy storage devices, high energy pulsed power, functional switches, etc. These applications require a deep understanding of the phase transition behaviors and energy transition properties under pressure, to manipulate the order parameters in these materials. Previously, most of the investigations focused on lead zirconate titanate (PZT) ferroelectric compounds, due to their high energy density, excellent output properties and acceptable stability. In 1957, Neilson et al. reported the depolarization of the PZT ferroelectric ceramics under the compression with an energy output observed. After that, many researchers explored this field. The energy transition behaviors, structure changes, dielectric properties, resistivity, and mechanical properties of the PZT based compounds have been systemically investigated, and the compounds include PZT (PZT 95/5 = PbZr0.95Ti0.05O3, PZT 52/48, PZT 30/70, etc.), PZST (Pb(Zr/Sn/Ti)O3), PMN-PT (Pb(Mg1/3Nb2/3)-PbTiO3), and their solid solutions, etc. Among these ferroelectrics, BaTiO3 was the only lead free ferroelectric studied, but it did not obtain any more interest due to the low energy output; and PZT based materials have dominated this field for more than half century. However, the further improvement of their properties is very challenging because of the limitation of their ferroelectric properties. Moreover, PZT based compounds produced serious environment problem, so there is a strong demand for lead-free ferroelectric materials to substitute these compounds. Here, we explored the phase transition and energy output properties of Na0.5Bi0.5TiO3 (NBT) ceramics under dynamic compression. NBT was chosen is due to its high remnant polarization (Pr), relatively high Curie temperature (Tc) and lead free. Surprisingly, a giant electrical output was observed and a power density of 3.04*10^8 W/kg was achieved, which is higher than all the ferroelectric materials studied previously. The hugoniot state and pressure ? volume curve were established to reveal the phase transition of NBT under shock compression. The structure details of this phase transition was investigated by static pressure experiments with X-ray diffraction (XRD). A comprehensive picture of this phase transition was developed by first principle simulation. These results would be of importance for the development of the relative applications.

Authors : Ru-song Li, Du-qiang Xin, Shi-qi Huang, Jin-tao Wang, Zhi-jian Wang
Affiliations : Xijing University

Resume : We perform first principle calculations on NiO system using various density functional theory (DFT) and hybrid functional methods inclusion of spin polarization (SP), on-site Coulomb repulsion U and spin-orbit coupling (SOC) effects. It is shown that localized spin density approximation (LSDA) plus U (LSDA+U) correctly reproduce experimental lattice parameter, while spin polarization generalized gradient approximation (SP+GGA+U) obviously overestimates lattice parameter. LSDA+U/SP+GGA+U band gaps and magnetic moments are in agreement with experimental data, and correctly predict NiO to be a insulator. NiO undergoes a metal-insulator transition by addition of Coulomb interaction. Our LSDA+SOC results show that SOC further splitting of Ni d eg and t2g orbitals into dz2, dxy, dx2y2 and dxz+dyz orbitals, SP nearly cancels out SOC effect, giving rise to symmetry of both TDOS and PDOS for spin-up and spin-down states, thus zero net magnetic moment occurs. For LSDA+U+SOC calculation, combination effect of SP, U and SOC results in un-occupation of spin-up conduction band and a negligible density of states for spin-down states.

Authors : Bidhan Chandra Patra, Anirban Pradhan, Santanu Bhattacharya
Affiliations : Director’s Research Unit, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata-700032, INDIA.

Resume : Metal-free catalysis for electrocatalytic hydrogen evolution from water is very demanding for the production of sustainable and clean fuel. Herein, we present the synthesis of a porphyrin-based metal-free covalent organic polymer TpPAM, which exhibited higher hydrogen evolution reaction (HER) activity than those of other metal-free engineered materials, such as conjugated microporous polymers (CMPs). The as-prepared porous TpPAM exhibited superior activity for the (HER) at 10 mA/cm2 at a low overpotential of 250 mV and a small Tafel slope of 106 mV/decade, which are better than those of related metal-free electrocatalysts. The high HER activity of TpPAM was investigated in-depth via theoretical density functional theory (DFT) calculations. The theoretical findings were correlated with the experimental results, and these were in good agreement for high HER catalytic efficiency of the porous TpPAM polymer. The Faradaic efficiency of the TpPAM-based electrode was found to be 98%, which is very close to the ideal value of 100%, reflecting its potential for practical implementation. Moreover, the as-synthesized catalyst showed good stability by retaining 91% of the initial current density after 1000 cycles.

Authors : Tae-Ho Lee1; Hyun-Gyu Hwang2; Seonghoon Jang2; Gunuk Wang2; Seongbeom Han2; Dong-Hwee Kim2; Chong-Yun Kang2,3; Sahn Nahm1,2
Affiliations : 1 Department of Materials Science and Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea; 2 Department of Nano Bio Information Technology, KU-KIST Graduate School of Converging Science and Technology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea; 3 Electronic Materials Center, KIST, 39-1 Hawolkok-dong, Seongbuk-gu, Seoul 137-791, Republic of Korea

Resume : Amorphous KNbO3 (KN) film containing KN nanocrystals was grown on TiN/SiO2/Si substrate at 350oC. This KN film showed a dielectric constant (?r) and piezoelectric strain constant (d33) of 43 and 80 pm/V at 10 V, respectively, owing to the existence of KN nanocrystals. Piezoelectric nanogenerators (PNGs) were fabricated using KN films grown on the TiN/Polyimide/PET substrates. PNG fabricated with the KN film grown at 350oC showed an open-circuit output voltage of 2.5 V and a short-circuit current of 70 nA. The KN film grown at 350oC exhibited a bipolar resistive switching behavior with good reliability characteristics that can be explained by the formation and rupture of the oxygen vacancy filaments. The KN resistive random access memory device powered by the KN PNG also showed promising resistive switching behavior. Moreover, the KN film shows good biocompatibility. Therefore, the KN film can be used for self-powered artificial synapse.

Authors : D.A. Osinkin 1.2, N.I. Lobachevskaya 3, N.M. Bogdanovich 1, N.M. Porotnikova 1.2
Affiliations : 1 Institute of High-Temperature Electrochemistry, 620137, Yekaterinburg, 20 Academicheskaya St., Russia; 2 Ural Federal University, 620002, Yekaterinburg, 19 Mira St., Russia; 3 Institute of Solid State Chemistry, 620990, Yekaterinburg, 91 Pervomayskaya St., Russia;

Resume : Symmetrical solid oxide fuel cells (sSOFC), in which the same electrode material is used for the anode and cathode, are promising energy converter systems. The use of the same material can simplify the fabrication process, improve the chemical and thermal compatibility, reduce the costs etc. In addition, the anode degradation towards sulfur poisoning and carbon deposition can be recovered by switching the anode and cathode gases. However, the conventional electrode materials are unsuitable for preparation of sSOFC electrodes. Therefore, the development of new materials for sSOFC is of great current interest. The Sr1.9Sm0.1Fe1.5Mo0.5O6-? powder, synthesized in air, had a small admixture of SrMoO4. At 800 °C the ASR values (?·cm2) were: 0.6 for air, 1.5 for Ar, 0.25 for 5%H2+Ar, 0.15 for wet (3%H2O) hydrogen and 0.5 for 0.8CO+0.2CO2. The electrochemical performances of the electrodes, measured in CO+CO2 mixtures, increased with an increase in as the CO partial pressure up to 0.8CO+0.2CO2. The electrodes were tested for 150 hours at 800 °C in 0.5CO+0.5CO2 and their electrochemical performances were found to improve. Seven cycles of changing the atmosphere from air to wet hydrogen at 800 °C were performed with the exposure in each atmosphere about 20 hours. The results showed no significant changes in the characteristics of the electrodes after red-ox cycling. The study was partly financially supported by the Russian Foundation for Basic Research (Project No. 17-08-00161).

Authors : D.A. Osinkin 1.2, I.V. Korzun 1, S.M. Beresnev 1, A.V. Khodimchuk 1.2, A.Yu. Suntsov 3, B.V. Politov 3.
Affiliations : 1 Institute of High-Temperature Electrochemistry, 620137, Yekaterinburg, 20 Academicheskaya St., Russia; 2 Ural Federal University, 620002, Yekaterinburg, 19 Mira St., Russia; 3 Institute of Solid State Chemistry, 620990, Yekaterinburg, 91 Pervomayskaya St., Russia;

Resume : Oxide fuel electrodes are subjects of intense research in the field of solid state electrochemistry. To date, the most studied oxide anodes are doped titanium, chromium and manganese oxides. However, they do not have the practical application due to their low conductivity and electrochemical activity, chromium evaporation and secondary phase formation on the electrolyte/electrode boundary etc. A new promising direction is the development of the anode materials based on strontium ferrite. The synthesized in air compounds Sr1-xCaxFe0.75Mo0.25O3-? (x = 0.05, 0.15, 0.3) did not have any impurity phases. After high-temperature treatment in reducing atmosphere at 800 °C the powders remained single-phase. By means of TGA and DSC in air, argon and 5%H2+Ar atmospheres the thermal effects and mass changes were studies. The maximum total electrical conductivity was approximately 35 S/cm at 800 °C at x = 0.3 in wet hydrogen. The smallest ASR value of about 0.1 ?·cm2 at 800 °C in wet hydrogen was obtained at x = 0.15. The studies of single fuel cell with the supported (thickness 1.2 mm) LaGaO3-based electrolyte and 70 wt.% Pr0.9Y0.1BaCo2O6-? + 30 wt.% SDC cathode showed the maximum power density of about 0.3 W/cm2 at 800 °C under wet hydrogen/air conditions. The overvoltage of the cathode and anode under these conditions at the current density of 1 A/cm2 does not exceed 0.1 V. The study was partly financially supported by the Russian Science Foundation (Project No. 17-79-10207).

Authors : Woong-Hee Lee1; Sang-Hyo Kweon1; Mir Im2; Sahn Nahm1,2
Affiliations : 1 Department of Materials Science and Engineering, Korea University, 1-5 Ga, Anam-Dong, Seongbuk-Gu, Seoul 136-701, Korea; 2 Information Technology-Nano Science, KU-KIST Graduate School of Converging Science and Technology, Korea University, 1-5 Ga, Anam-Dong, Seongbuk-Gu, Seoul 136-713, Korea

Resume : Pseudocapacitors fabricated using the metal oxide-based materials have been widely investigated because they showed the higher specific capacitance than the electric-double-layer capacitors. Recently, a new type of pseudocapacitor, which is produced using two-dimensional metal oxides, has been reported and the charge and discharge processes of these pseudocapacitors were explained by the cation intercalation mechanism. Particularly, a planar-type pseudocapacitor has been intensively studied because the smooth cation migration occured in this pseudocapacitor. Herein, the pseudocapacitors were fabriated using the Sr2Nb3O10- (SNO) nanosheets and their eletrochemical properties were investigated. The SNO nanosheets were obtained from KSr2Nb3O10 (KSN) ceramics using soft-chemical exfoliation. These SNO nanosheets have a large aspect ratio that is useful for the ultra-thin film pseudocapacitor. The exfoliated SNO nanosheets were deposited on a Pt/glass substrate with a planar-type pattern to fabricate two symmetric working electrodes. Langmuir-Blodgett(LB) method was used for the deposition of these SNO nanosheets at room temperature. These SNO electrodes showed the good specific capacitance of 270 uF/cm2 at current density of 2.5 uA/cm2 and the cycling stability with capacitance retention of 86% after 5000 charge/discharge cycles in PVA/LiCl electrolyte. In addition, the structural and electrochemical properties of the SNO electrodes with various thicknesses will be presented in this work.

Authors : Subhajit Pan, Koushik Biswas
Affiliations : Research Scholar, Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, 721302, India ; Associate Professor, Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, 721302, India

Resume : Solid oxide fuel cell (SOFC) is getting popularity because of its high efficiency, fuel flexibility, durability and eco-friendly energy conversion device. Till date, yttria-stabilized zirconia (YSZ) system has dominated the SOFC world. In which Ni/YSZ cermet is commonly used as the anode and yttria-stabilized zirconia (YSZ) is used as the electrolyte material. Despite of its high electrochemical activity and superior stability, Ni/YSZ cermet anodes show carbon deposition as well as rapid performance degradation when hydrocarbon fuels are used. Recently, perovskite La1?xSrxGa1?yMgyO3-? (LSGM) having oxygen vacancies is emerging as promising electrolyte material for its high ionic conductivity at low temperature and (LaA)(CrB)O3 system (A=Ca, Sr, and B=Mg, Mn, Fe, Co, Ni) as alternative anode materials for SOFC. In the present work, La0.9Sr0.1Ga0.8Mg0.2O3-? (LSGM) powder was synthesized by the glycine-nitrate process, and La0.7Sr0.3Cr0.5Mn0.5O3-? (LSCM) powder was synthesized by the solid-state process. Then LSGM electrolyte thin film was successfully fabricated on porous anode substrate of LSCM by pulsed laser deposition technique. Some technical parameters for the preparation of LSGM thin films were systematically investigated including power, temperature and time. The electrolyte films with the best compactness were found. To ensure, the proprieties are evaluated by XRD analysis and SEM. MicroCT scanning was done to find out the porosity distribution across the anode electrolyte bilayer. SEM results revealed that the LSGM film was crack-free, continuous and dense. Electrical properties were evaluated by impedance spectroscopic analysis.

Authors : Kyunho Jung1, Kyongmin Kim2, Seunggon Song1, Kyoungwan Park3
Affiliations : 1Department of Nano Science & Technology; 2Department of Nano Engineering; 3Department of Physics, University of Seoul, Seoul 02504, Korea

Resume : We fabricated ZnO-based Resistive Random Access Memory (RRAM) devices employing double ultra-thin SiOx(x< 2) layers in the ZnO thin film. The ZnO and SiOx thin films were deposited using a radio-frequency magnetron sputtering technique at room temperature. A bipolar resistive switching was investigated for nonvolatile memory applications. Set and reset voltages were ~ 1.7 V and ~-2.9 V, respectively. The high/low resistance state ratio was >10**5 at reading voltage of 0.3 V during >10**4 set/reset cycles. The set/reset times were less than 100 nsec. We expected the retention time to be longer than 10**8 sec. This RRAM device exhibited not only better nonvolatile memory properties but also lower power consumption in the on/off operations, as compared to those of previous ZnO-based RRAMs. The results show that the ultra-thin SiOx(x< 2) double layers play an effective role for the repeatable formation/rupture of conducting filaments in the ZnO thin film and low current operation in the set/reset processes. Because an asymmetric conducting filament has a weak point for charge conduction in the ultra-thin SiOx layer, we attributed the good nonvolatile memory properties to the reproducible formation/rupture of ?micro?-conducting filaments at the weak points. In addition, the dynamics of the oxygen ions in the multi-layers play an important role in the resistive switching.

Authors : Abdel El kharbachi (a), Astrid B. Høgset (a), Sangryun Kim (c), Ponniah Vajeeston (b), Magnus H. Sørby (a), Helmer Fjellvåg (b), Shin-ichi Orimo (c,d), Bjørn C. Hauback (a)
Affiliations : (a) Institute for Energy Technology, P.O. Box 40, NO-2027 Kjeller, Norway ; (b) Centre for Materials Science and Nanotechnology, University of Oslo, Blindern, Norway ; (c) Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan ; (d) WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.

Resume : The glass system Li2S-P2S5 has been extensively studied as electrolyte for application in all-solid-state Li-ion batteries. The addition of lithium halides to glass electrolytes has been shown to improve the ionic conductivities and form favorable contacts at the electrode/electrolyte interface [1]. Recently, the LiBH4-Li2S-P2S5 system has attracted attention owing to its interesting ionic properties for solid state battery electrolytes [2,3]. LiBH4 is a good Li-ion conductor only above its solid state phase transition temperature (Ttr ~110°C). The high-T phase can be stabilized by partly substituting BH4- with halides, e.g. Li(BH4)0.75I0.25, thus preserving high ionic conductivity on cooling down to RT. The present work deals with the investigation of the properties of the Li(BH4)1-yXy (X = Cl, Br, I) phases when embedded in a 0.75Li2S·0.25P2S5 amorphous matrix for application in all-solid-state lithium batteries. The mixed systems are prepared by ball-milling and annealing procedures and their ionic conductivities were studied in a wide composition range by varying the weight ratio. The study is supplemented by electrochemical stability (I-E) measurements, vibrational spectroscopy (FTIR/Raman), DFT calculation and in-situ X-ray diffraction during battery cycling of the optimized compositions. References [1] Ujiie et al., Solid State Ionics, 211 (2012) 42-45. [2] Yamauchi et al., J. Power Sources, 244 (2013) 707-710. [3] Unemoto et al., Chem. Commun., 52 (2016) 564-566.

Authors : Xinqiang Pan,1,2 Yao Shuai,1* Chuangui Wu,1 Wenbo Luo,1 Xiangyu Sun,1 Huizhong Zeng,1 Hongliang Guo,3 Ye Yuan,4 Shengqiang Zhou,4 Roman Böttger,4 Hong Cheng,3 Jianwei Zhang,2 Wanli Zhang,1 and Heidemarie Schmidt 5,6
Affiliations : 1. State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China; 2. TAMS Group, Department of Informatics, University of Hamburg, D-22527, Hamburg, Germany; 3. The Center for Robotics, University of Electronic Science and Technology of China,Chengdu 611731, China; 4. Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstr. 400, 01328 Dresden, Germany; 5. Fraunhofer-Institut für Elektronische Nanosysteme, Abteilung Back-End of Line, Technologie-Campus 3, 09126 Chemnitz, Germany; 6. Leibniz-Institut für Photonische Technologien e.V. (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany

Resume : Recently, memristive behavior and corresponding memristive device have been investigated intensively due to its great potential in non-volatile memory and neuromorphic computing. It is well known that oxygen vacancies (OVs) play a significant role in the memristive behavior of metal-oxide-based memristive devices. But OVs tend to aggregate near the grain boundaries in polycrystalline thin film, which makes the investigation on the behavior of OVs become complicated and leads to the large deviations of resistive switching properties in the area covered with grain and the area covered with grain boundaries. In order to investigate the behavior of OVs in the memristive behavior further and improve the uniformity of the performance of memristive devices to meet the requirements for its future application, the coexistence of grain and grain boundaries need to be avoided, and the density of intrinsic defects need to be low. Single crystalline oxide material, including oxide single crystal and single crystalline oxide thin films, provide us an ideal platform to create and manipulate the OVs density and distribution. In the present work, vacuum-annealing process and laser annealing process were used to generate OVs and control the amount of OVs in the SrTiO3 (STO) single crystal. In the memristive cells on the vacuum-annealed STO single crystal, the forming-free resistive switching behavior with self-compliance property was observed. Such behavior was based on the switchable diode effect which was explained by the redistribution of OVs under the electrical field[1]. In the STO single crystals annealed by laser, with the increase of the laser fluence, the amounts of OVs increase, which leads to the increase of the leakage current. And resistive switching behavior is only observed in the sample annealed by laser with relatively high fluence after an electro-forming process, which indicates that resistive switching appears only when enough oxygen vacancies are generated by the laser to form the conductive filament[2]. However, the study on the single crystal is conducted with the lateral structure which is not an appropriate structure for practical application, so it is significant to study the memristive behavior of single crystalline thin film with vertical structure. In the present work, single crystalline LiNbO3 thin films which were fabricated by crystal ion slicing technique were used. The thin films were annealed in vacuum and Ar gas atmosphere to create OVs and control the amount of OVs in the thin film. The electro-forming processes of different cells on the same sample show good uniformity. After the electro-forming process, the properties of resistive switching behavior are controllable and show high reproducibility. Rectifying filamentary resistive switching behavior is interpreted by a simplified model that the local filament composed of OVs does not penetrate throughout the LNO thin film[3]. Reference: [1] Pan, X.; Shuai, Y.; Wu, C.; Luo, W.; Sun, X.; Zeng, H.; Bai, X.; Gong, C.; Jian, K.; Zhang, L.; Guo, H.; Tian, B.; Zhang, W. Applied Physics A 2017, 123, (9). [2] Pan, X.; Shuai, Y.; Wu, C.; Luo, W.; Sun, X.; Yuan, Y.; Zhou, S.; Ou, X.; Zhang, W. Applied Surface Science 2016, 389, 1104-1107. [3] Pan, X.; Shuai, Y.; Wu, C.; Luo, W.; Sun, X.; Zeng, H.; Zhou, S.; Böttger, R.; Ou, X.; Mikolajick, T.; Zhang, W.; Schmidt, H. Applied Physics Letters 2016, 108, (3), 032904.

Authors : Xiaoyuan Bai,1Yao Shuai*,1Chaoguan Gong,1Chuangui Wu*,1Wenbo Luo,1Roman Böttger,2Shengqiang Zhou,2Wanli Zhang,1
Affiliations : 1. State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China 2. Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, BautznerLandstr. 400, 01328 Dresden, Germany

Resume : Single crystalline LiNbO3 (LN) thin films with different cuts have been fabricated successfully on the LN substrates by means of crystal-ion-slicing (CIS) technology. And on this basis it is proved that local conductive filaments are formed on the single crystalline Z-cut LN thin films as electro-forming takes place and it shows rectifying filamentary switching properties because the filaments composed by oxygen vacancies do not penetrate throughout the LN thin film [1]. Single crystalline 128°Y-cut thin films for surface acoustic wave (SAW) devices and 36°Y-cut LN thin films for bulk acoustic wave resonators (BAR) with a high crystalline quality are also obtained using CIS technology [2]. High density of pillars from AFM measurement existing on the LN thin film surface after exfoliation are indicated, which is treated adopting low energy Ar+ irradiation. It is proved that a surface amorphous layer can be etched more efficiently than interior single crystalline lattice and obtained a more smoother surface by low energy Ar+ irradiation, which is a general process that can be adopted to implement surface modifications on other CIS-fabricated thin films as well [3]. The effects and influence of different bottom electrodes on the ferroelectric properties has been studied for CIS-fabricated 36°Y-cut LN single crystalline thin films. References [1] Pan X, Shuai Y, Wu C, Luo W, Sun X, Zeng H, et al. Rectifying filamentary resistive switching in ion-exfoliated LiNbO3 thin films. Applied Physics Letters 2016;108:032904. [2] Shuai Y, Gong C, Bai X, Wu C, Luo W, Böttger R, et al. Extended Abstracts of the 2017 International Conference on Solid State Devices and Materials, Sendai, 2017, pp919-920. [3] Bai X, Shuai Y, Gong C, Wu C, Luo W, Böttger R, et al. Surface modifications of crystal-ion-sliced LiNbO 3 thin films by low energy ion irradiations. Applied Surface Science 2018;434:669-73.

Authors : Rupali Singh, Koushik Biswas
Affiliations : Research Scholar, Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur -721302, INDIA; Associate Professor, Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur -721302, INDIA.

Resume : Renewable energy sources say solar, wind and geothermal are very popular nowadays due to lack of traditional fossil fuels and crude oil sources. The development and research of storage devices or rechargeable batteries (Li/Na/Mg - ion) are increasing for storing the energy. Nowadays the Li-ion batteries are very popular in the world for storing the energy. However, a limitation of lithium batteries is the dendrite formation, inherently unsafe and costly also. In recent time, the magnesium metal is increasing attention because it has higher volumetric capacities, low electrode potential, and high charge density, and also provides low-cost batteries due to it is the most abundant natural element in the earth crust. The spinel structure MgFeTiO4 was prepared by using Solid state route and the structural, vibrational, electrical characterization of the compound was investigated. The crystal structure has been identified by Rietveld analysis of powder X-ray diffraction data. These results show a spinel-type structure in which all titanium cations are in octahedral sites whereas magnesium and iron cations are distributed on tetrahedral and octahedral sites. FTIR?Raman spectroscopy indicates the presence of Mg2TiO4 phase with Fe2TiO4 was also identified from both FTIR and Raman spectrum. The electrical and dielectric properties of the sample were studied at different temperatures from room temperature to 300 oC by using solid-state impedance spectroscopy. The DC conductivity of material was observed and found a maximum dc conductivity at 300 oC. The calculated activation energy from dc conductivity was found to be 0.174 eV confirms the semiconducting behavior of the materials.

Authors : Plawan Kumar Jha, Santosh Kumar Singh, Vikash Kumar, Shammi Rana, Sreekumar Kurungot, and Nirmalya Ballav
Affiliations : Plawan Kumar Jha; Vikash Kumar; Shammi Rana; Nirmalya Ballav, Department of Chemistry, Indian Institute of Science Education and Research (IISER), Dr. Homi Bhabha Road, Pune, Maharashtra ? 411 008; India. Center for Energy Science, Indian Institute of Science Education and Research (IISER), Dr. Homi Bhabha Road, Pune, Maharashtra ? 411 008, India. Santosh Kumar Singh; Sreekumar Kurungot, Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory (NCL), Dr. Homi Bhabha Road, Pune, Maharashtra ? 411 008, India

Resume : Graphene-based materials are emerging as smart alternatives to activated carbon used in commercial supercapacitor. Here, we present chemical reduction of graphene oxide (GO) in aqueous medium by an unconventional mild reducing agent (FeCl2/HCl) where self-assembled reduced graphene oxide (rGO) is isolated and the reducing agent is recycled upon simple treatment of the filtrate with HCl. The fabricated all-solid-state supercapacitor of as-synthesized rGO exhibited significantly higher specific capacitance (171 F/g at 1.1 A/g), remarkable cycling stability (>80% retention of capacitance beyond 100,000 continued cycles), and flexibility (>500 bending cycles), which is comparatively much better than those of rGO derived from conventional reducing agents like NaBH4 and N2H4. Use of organic electrolyte further boosted the supercapacitor performance (282 F/g at 1.8 A/g) of rGO. This work opens up new possibilities for the production of rGO on an industrial scale satisfying the needs of high-performance energy-storage devices.

Authors : Neelakshi Sharma, Anshuman Dalvi
Affiliations : Birla Institute of Technology and Science-Pilani

Resume : A novel mechanical ball milling assisted synthesis route has been used to prepare new generation Li ion glass-ceramic composites using (i) glassy system (Li2SO4)x-(LiPO3)100-x (x=30-60 mol%, abbreviated as LSLP) and (ii) Li -NASICON, i.e., LiTi2(PO4)3 known as LTP. Initially ionic glass (x=60 mol%, i.e. 60LSLP) was chosen and its content was varied in (60LSLP)y-(LTP)100-y matrix for y=5-20 wt %. To prepare the composite, both the LTP as well as LSLP glass were separately milled for 3-18h, mixed and subsequently pelletized. These pellets were later subjected to thermal treatment at 700-900 OC for various annealing times. Annealing above the melting temperature of glass leads to glass-ceramic formation. Thus various parameters for e.g., milling time, glass to NASICON ratio, annealing temperature and annealing time affect the ionic transport. These were further optimized in order to get a highly conducting and thermally stable composite. The highest grain (7.2×10-4 ?-1 cm-1) and grain boundary (4.2×10-5 ?-1 cm-1) conductivity values were obtained for a glass-ceramic prepared from 18h milled LSLP and LTP, with composition 20%(60LSLP)- 80%(LTP) when it was annealed at 800 oC for 30min. The XRD patterns suggest that no new compound formation takes place in the resultant glass-ceramic. Further, differential scanning calorimetry scans confirm the formation of glass-ceramic. FESEM results suggest that milling effectively reduces the LTP crystallite size to 30-40 nm in the composite matrix. The overall electrical transport is significantly higher in the novel glass-ceramics in comparison to LTP prepared with similar annealing conditions.

Authors : Mijeong Han, Jungdon Suk, Yongku Kang
Affiliations : Korea Research Institute of Chemical Technology

Resume : Solid polymer electrolytes(SPEs) for lithium ion batteries have been attracted to the substitutes for the liquid electrolytes which caused the important safety problems due to the volatile organic solvents. SPEs generally include crosslinker, initiator, plasticizer, and lithium salt, and the acrylates have been most widely used as crosslinkers. Since acrylates are sensitive to water and oxygen which interrupt the polymerization and are difficult to handle, we have synthesized new thiol-ene crosslinkers that are less sensitivity and have good storage stability. The new crosslinkers with triazine core with branched structures were synthesized by varying the number of branches to 3 and 6, and the length of the ethylene oxide chain involved in lithium ion transfer was also controlled. The electrochemical properties of new crosslinkers were examined varying the chain length of EO group, the ratio of plasticizer to crosslinker, and the concentration of lithium salt. In-situ thermal curing of the SPE was carried out, and the ionic conductivities of SPEs depending on temperature were measured. The ion conductivity of the optimized solid polymer electrolyte was improved to 3.6 × 10 -4 S / cm at 30 oC compared to the conventional PEO system (10-6~10-8 S / cm). The electrochemical stability was investigated for confirming the lithium transfer capability and the wide electrochemical window of 5V or more through CV and LSV analysis, respectively.

Authors : Lalit Sharma, Ritambhara Gond, Prabeer Barpanda
Affiliations : Lalit Sharma, Faraday Materials Laboratory, Materials Research Center, Indian Institute of Science, Bangalore 560012, India; Ritambhara Gond, Faraday Materials Laboratory, Materials Research Center, Indian Institute of Science, Bangalore 560012; Prabeer Barpanda, Faraday Materials Laboratory, Materials Research Center, Indian Institute of Science, Bangalore 560012

Resume : In the era of metal-ion batteries, where lithium and sodium ion batteries currently dominate the energy sector, the constant increase in the demand for energy requires a storage device having high energy density. Air batteries are one such option to explore as lithium-air battery exhibits a theoretical energy density of 5200 Whkg-1 while the sodium-air batteries are not explored much. Aqueous system based air batteries have upper hand over non-aqueous air batteries as the discharge product is soluble in water and hence do not clog the active sites. Motivated by various cobalt phosphate-based materials being reported as an electrocatalyst, we tried to study the electrocatalytic properties of Na2CoPO4F synthesized via solution combustion route. It was found to exhibit bifunctional nature with good oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) properties. It gave an onset potential of 0.945 V vs. RHE during ORR and 1.54 V vs. RHE during OER marking it as an efficient bifunctional electrocatalyst. It also showed better stability than Pt/C in terms of ORR. Due to its bifunctional nature, it was studied as a cathode for sodium air-batteries in an aqueous system (0.1 M NaOH). This work will describe (i) complete synthesis process, (ii) structural and electrochemical properties, (iii) air-battery performance of Na2CoPO4F, and (iv) electrocatalytic properties of Na2MPO4F (M= Fe, Mn, Co, Ni) fluorophosphates.

Authors : Minwoo Ahn, Joungseo Lee, Wonyoung Lee
Affiliations : Sungkyunkwan University; Sungkyunkwan University; Sungkyunkwan University

Resume : A solid oxide fuel cell (SOFC) is one of the most promising energy conversion devices because of its high efficiency, environmental friendliness, easy scale up, and fuel flexibility for various applications ranging from small-scale portable devices to large-scale distributed power plants. To relieve the operating temperature of SOFCs from high temperatures (800-1000 °C) to intermediate temperatures (500-700 °C) for wider application, a number of approaches have been developed. Since the cathode loss increase drastically for the sluggish oxygen reduction reaction (ORR) as operating temperature decrease and occupies dominant fraction of total resistance, cathode design is the key strategy for performance enhancement. We develops the Sm0.5Sr0.5CoO3-? (SSC) nanofiber-based composite cathode, showing a cathode area-specific resistance (ASR) value of 0.024 ?cm2 at 650 °C which is the 5-fold enhanced electrode resistance than conventional SSC powder cathodes. The hollow and porous SSC nanofiber layer, fabricated by electrospinning, is sintered at low temperature to preserve the high specific surface area. The low fabrication temperature is enabled by the powder adhesion layer, providing sufficient adhesion between the electrolyte and the nanofiber layer. Our results can provide a design guideline to fully utilize the nanostructured electrodes by engineering the structural properties, and hence high-performing SOFCs can be achieved by the structural modification.

Authors : Zhuoxin Liu,Chunyi Zhi
Affiliations : City University of Hong Kong

Resume : High-performance energy storage devices are in urgent need due to the fast development of wearable electronics, while the challenge of achieving outstanding flexibility has not been properly addressed yet, let alone the safety, another critical issue determines their practicability. Herein, we report a quasi-solid-state aqueous rechargeable lithium-ion battery (ARLIB) based on carbon cloth substrates and PVA-LiNO3 gel polymer electrolyte (GPE). Thanks to the protective PPy coating layer on LiV3O8 and the use of solid GPE, the as-assembled ARLIB exhibits a good cycling stability of 98.7% and 79.8% capacity retention after 100 and 500 cycles, respectively. It also demonstrates exceptional flexibility to sustain various deformations including bending, squeezing, twisting and folding because of its solid-state design. Moreover, the ARLIB can be tailored into any desired shapes, and even be punched penetrative holes, exhibiting excellent safety. Thus, the creation of numerous tiny through-holes across the whole ARLIB body is testified feasible, and a designed breathability catering to the demand of comfortability in wearable devices is subsequently realized. Obviously, our study offers a promising strategy to construct flexible energy storage device with outstanding stability, flexibility, safety and breathability towards various wearable electronics.

Authors : Si-Won Kim, Jongsup Hong, Jong-Heun Lee, Mansoo Park, Kyung Joong Yoon, Jong-Ho Lee
Affiliations : SW Kim, M. Park, K. J. Yoon, J.-H. Lee (High-temperature Energy Materials Research Center, KIST, Seoul 02792, Korea) J. Hong (Department of mechanical Engineering, Yonsei University, Seoul 03722, Korea) J. Lee (Department of Materials Science & Engineering, Korea University, Seoul 02841, Korea)

Resume : In recent years, various attempts have been made to develop a high-capacity energy storage device in order to increase the availability of renewable energy. In this regard, syngas production by high-temperature co-electrolysis of CO2/steam mixtures using renewable energy sources is the most effective way to reduce CO2 emission in connection with renewable energy. Recently, we confirmed the possible operation of high-temperature co-electrolysis using existing solid oxide cells (SOC) which has been used for solid oxide fuel cell (SOFC). However, syngas production rate during co-electrolysis operation was still not enough to secure economical efficiency. The low production efficiency was mainly due to the limited function of Ni-based catalysts in conventional fuel electrode of SOC. Hence, in this study, conventional fuel electrode was modified to have multi-scaled catalyst structure that can promote the catalytic reaction, especially the reverse water gas shift (RWGS) reaction, thereby increasing the CO2 conversion efficiency. In-situ nano-alloying technique being suitable to incorporate small amount of precious metal catalysts into fuel electrode was employed to realize the multi-scaled catalyst structure. According to the analysis on the selectivity and the rate of syngas production, multi-scaled catalyst structure was very efficient to improve the overall co-electrolysis efficiency.

Authors : Hongfei Li; Chunyi Zhi
Affiliations : Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR, China; Shenzhen Research Institute, City University of Hong Kong, Shenzhen, 518000, China

Resume : The emerging research toward the next-generation flexible and wearable electronics has stimulated the efforts to build highly wearable, durable and deformable energy devices with excellent electrochemical performances. Herein, we report the first paradigm of a solid-state washable and tailorable elastic yarn zinc ion batteries (ZIB) constructed by a novel polyacrylamide (PAM) based polymer electrolyte . To achieve a stable electrochemical performance under the repetitive deformation conditions, for the first time, we developed the PAM as the polyelectrolyte matrix host for the neutral solution of zinc sulfate and manganese sulfate. Benefiting from the good compatibility between metal salts and PAM, the developed polymer electrolyte possesses a high ionic conductivity and exceptional strength, which greatly enhance the rechargeability of the fabricated ZIBs. Multi-helix carbon nanotube (CNT) yarns were used as substrates for the MnO2 cathode and zinc anode, which effectively enhance the strength and robustness of the electrodes under different deformation conditions and significantly improve electrolyte wetting of the electrode surface. The solid-state yarn ZIB delivers a high specific capacity and volumetric energy density (302.1 mAh g-1 and 53.8 mWh cm?3, respectively) as well as excellent cycling stability (98.5% capacity retention after 500 cycles at a high current of 2 A g-1). Moreover, the quasi-solid-state yarn ZIB also demonstrates excellent flexibility and can be elastically stretchable (up to 300% strain) and maintained a high capacity retention of 96.5% after 12 h continuous underwater operation in DI water. Besides, 1 m long yarn ZIBs were tailored and woven into a battery textile that could power a long LED belt and a 100 cm2 electroluminescent panel. This yarn battery offers a new platform for flexible and wearable technologies.

Authors : Jordi Sastre-Pellicer; Tzu-Ying Lin; Alejandro N. Filippin; Michael Rawlence; Stephan Buecheler
Affiliations : Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland

Resume : Garnet-type Li7La3Zr2O12 (LLZO) electrolyte is a promising ionic conductor for the development of all-solid-state thin film batteries. In bulk, this type of electrolyte has demonstrated high ionic conductivities in its cubic phase (around 1·10^-3 S/cm) as well as a wide electrochemical stability window (above 4 V against lithium). However, if deposited as a thin film, the ionic conductivities reported so far lag behind by some orders of magnitude. In this work, LLZO thin films have been realized using magnetron sputtering and post-annealing in a controlled-atmosphere furnace. Regulating the amount of lithium in the film and adding three-valent elements (e.g. Al) as sintering agents and phase stabilizers has allowed us to control the phase formation (from tetragonal to cubic) as well as the density of the films. The crystal phases have been investigated using grazing-incidence X-ray diffractometry. Scanning electron microscopy and time-of-flight secondary ion mass spectrometry have been used to assess the density and the distribution of substitutional element in the film. The ionic conductivity has been measured by in-plane impedance spectroscopy, resulting in values around 2·10^-5 S/cm at room temperature for mixed-phase LLZO thin films (400 nm). Our results reveal that the key factor for improving ionic conductivity of LLZO thin films consists not only in achieving a cubic phase, but also in increasing the density of the film.

Authors : ByeongSu Kang1, Young-Wan Ju3, Tatsumi Ishihara1,2
Affiliations : 1 Department of Automotive Science, Graduate School of Integrated Frontier Science, Kyushu University, Fukuoka 819-0395, Japan; 2 International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University Fukuoka 819-0395, Japan; 3 Department of Chemical Engineering, College of Engineering, Wonkwang University, Iksan, Jeonbuk 54538, Korea

Resume : Solid oxide fuel cells (SOFCs) have been attracting much interest as energy conversion devices from chemical energy to electrical energy. The high operation temperature is, however, strongly required to decrease for wide application of SOFCs. By decreasing temperature, electrode overpotential, in particular oxygen reduction reaction (ORR) at cathode, have been issued due to decrease in electrode activity. The cathodic performance can be improved significantly to control the length of thee phase boundary (TPB). Our previous study suggested that to achieve improved cathodic activity, double columnar layer as active interlayer, consisted of Sm0.5Sr0.5CoO3 (SSC) and Ce0.8Sm0.2O3 (SDC), was introduced between LaGaO3 based electrolyte film and SSC cathode power by using pulsed laser deposition method. In this study, the composition of the SSC-SDC double columnar layer was optimized and mechanism for increased activity was investigated. The double columnar layer was fabricated on the SDC and La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) bi-layered film prepared by PLD method. SSC and SDC peaks patterns were observed by using XRD measurement in the deposited film. According to SEM-EDX and STEM-EDX, the double columnar structure was clearly identified with dense contact at the interface between SSC and SDC. The enhanced power generation properties, almost the theoretical open circuit potential (1.10V) and extremely high maximum power density around 3.0W/cm2 at 700oC, were achieved by introducing double column layer SSC:SDC 6:4. The double columnar layer showed significant small cathodic overpotential from current interruption analysis, impedance analysis also indicates small diffusion resistance even at 500oC. Cathodic activity on double columnar layer was strongly affected by film composition. Therefore, the optimized SSC-SDC double columnar layer is highly effective to increased cathodic activity for low temperature operation.

Authors : Michele Bastianello (a,b), Mathias Elm (c), Silvia Gross (a)
Affiliations : (a) Dipartimento di Scienze Chimiche ICMATE-CNR, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy; (b) ICMATE-CNR, Padova, Italy; (c) Physikalisch-Chemisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany

Resume : Ferrites are an interesting class of ternary metal oxides with catalytic, electrical and magnetic properties [1-2]. An easy and green synthesis route based on the coprecipitation of oxalates and hydrothermal treatment allowed to obtain nano-dimensional crystalline zinc, nickel, cobalt and manganese ferrites, namely ZnFe2O4, NiFe2O4, MnFe2O4 and CoFe2O4, already at 135 °C without further purification or thermal treatment. Thanks to the mild and controllable reaction settings the chance to tune the crystallite form and anisotropy through the was investigated and monitored by X-ray diffraction analysis. A combined structural characterization of the obtained materials was carried out with X-ray diffraction, inductively coupled plasma mass spectrometry and transmission electron microscopy pointed out the successful synthesis of single phase ferrites nanoparticles (10nm). Further investigations have being carried out, such as electrochemical impedance spectroscopy, catalytic tests, in order to relate structural to functional features of the synthetized material. [1] Rao et al. Wiley VCH. 2009 [2] K. Ali et al. J. Magnetism and magnetic Materials 2016, 434, 30-36

Authors : P. S. Ioannou1, E. Kyriakides1, C. Orfanidou1, O. Schneegans2, J. Giapintzakis1
Affiliations : 1Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Av., PO Box 20537, 1678 Nicosia, Cyprus; 2Group of Electrical Engineering of Paris (GeePs) UPMC and Paris-Sud Universities, CNRS, Centrale Supélec, Gif-sur- Yvette, France

Resume : Neuromorphic computing?the electronic equivalent of biological synaptic functionality?is emerging as one of the most viable successors of conventional von Neumann-based computing. However, energy efficiency and complexity limitations of neuromorphic-emulating architectures, based on CMOS three-terminal flash memory, impede the progress of neuromorphic computing, especially for mobile devices. This work introduces the ability to implement multilevel memory, as well as the emulation of biological synaptic functions in an elementary and efficient manner, using a Li ion-based two-terminal device. The thin-film device is based on a nearly stoichiometric PLD-deposited LiCoO2 layer, which facilitates the intercalation/deintercalation of Li ions. The devices discussed here are (1) Au/LiCoO2/TiO2/Ti/SiO2n/Si and (2) Au/LiCoO2/SiO2/TiO2/Ti/SiO2n/Si thin-film stacks. The TiO2 layer acts as a host matrix for the insertion of Li-ions. The SiO2 thin film?s role is established as a diffusion barrier for Li ions, which disrupts the formation of LixTiyO4 in device (2) during LiCoO2 deposition, leading to undesirably low ION/IOFF ratios, thus hindering the effects of resistive switching (RS) in the Li-deficient layer. With the use of programming pulses (±6 V), the Li concentration in the LiCoO2 layer is gradually altered, inducing RS. Excitatory Post Synaptic Current modulation in multiple distinct conductance states and plasticity are thus observed through a Paired Pulse Facilitation mechanism.

Authors : Seon-Joo Choi, Ji-Hyun Yu, Chil-Hoon Doh, Youjin Lee, Sang-Min Lee, Yoon-Cheol Ha
Affiliations : Korea Electrotechnology Research Institute (KERI)

Resume : Development of a tangible solid state battery has received great attention but there are various engineering challenges to overcome, especially for the scalable processing and the use of Li metal anode. In order to tackle these issues, we first evaluated the electrochemical stabilities of thio-LISICON solid electrolytes, i.e., Li10GeP2S12 (LGPS), Li7P3S11 (LPS), and Li7P2S8I (LPSI), where the glass-ceramic LPSI electrolyte showed a superior compatibility with Li metal. Moreover, a superionic conductivity of 1.35 x 10^-3 S/cm could be achieved by optimizing the wet mechanical milling and the low-temperature annealing processes. Using this superior LPSI solid electrolyte, we evaluated the electrochemical performance of pellet-type and slurry-type all-solid-state cells with LiNbO3-coated LiNi0.6Co0.2Mn0.2O2 (LNO-NCM622)/LPSI composite cathode and Li metal anode. The initial discharge capacity of ~150 mAh/g was achieved for the pellet-type test cell and ~120 mAh/g for the slurry-type cell. Comparing the interfacial resistances of the two types of cells, strategies to enhance the performance and realize a scale-up fabrication of all-solid state Li metal batteries are discussed.

Authors : Julie Bonkerud(1), Christian Zimmermann(1), Frank Herklotz(2), Edouard Monakhov(1), Lasse Vines(1), Bengt Gunnar Svensson(1)
Affiliations : (1) University of Oslo, Physics Department/Centre for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, Oslo N-0316, Norway; (2) Technische Universität Dresden, Institute of Applied Physics, 01062 Dresden, Germany

Resume : TiO2 in its rutile form is well-known for its photocatalytic properties [1], with a wide range of potential applications, including water splitting and water purification. A number of reports show that deposition of noble metals such as Pd and Pt onto TiO2 can improve the photocatalytic activity [2,3]. In addition, reduced and hydrogenated TiO2 has gained interest recently because it shows enhanced optical absorption and photocatalytic activity [4]. In the present study, we have fabricated rectifying junctions by depositing Pd and Pt on hydrogenated single-crystalline rutile TiO2. The Schottky diodes are analysed by Impedance Spectroscopy as well as temperature-dependent Current-Voltage (IV) and Capacitance-Voltage (CV) measurements. Barrier heights and ideality factors deduced from the experimental data are in the range of 0.8-1.0 V and 1.3-2 at room temperature, respectively. They show, however, a pronounced temperature dependence, which is modelled by different equivalent circuits describing the metal/semiconductor junction. The models take into account a highly-compensated interfacial layer between the metal and TiO2 which exhibits a high density of interface states. [1] A. Fujishima et al., Nature 213 (1972). [2] J. Wu et al., RSC Advances 6 (2016). [3] K. Maeda, Catalysis Science & Technology 4 (2014). [4] Z. Zheng et al., Chemical Communications 48 (2012).

Authors : Satoshi Muto, Shinya Sakai, Atsushi Tsurumaki-Fukuchi, Masashi Arita, Yasuo Takahashi
Affiliations : Graduate School of Information Science and Technology, Hokkaido University, Kita-14, Nishi-9, Kita-ku, Sapporo 060-0814, Japan

Resume : The CBRAM(conductive bridge RAM) is a type of the ReRAMs(resistive RAMs) and expected as a candidate for a next-generation non-volatile memory. For the future practical use and application, investigations using in-situ TEM(transmission electron microscopy) have been performed to understand a filament morphology during resistive switching. Such investigations found that a filament formation/rupture occurs at the read(set)/erase(reset) operation of CBRAM, the mobility of metal cation and redox rate in a solid electrolyte affect the mode of the filament formation, etc. However, there are few investigations about an operational instability of CBRAM like switching failure after many switching operations, despite their importance for an improvement of reliability and a structure optimization. To observe instable operations using in-situ TEM, we made Cu-WOx-Cu sample imitating CBRAM that was switched many times and deposited Cu at both electrodes. During a resistive switch to high resistance state(reset), current spikes caused by resistance instability were observed. Accompanied with the current spike, Cu filament was formed from the anode firstly, and then from the cathode. This result suggested that instable operations of CBRAM are complex phenomenon caused by not only electrochemical reactions but also heating and electromigration, etc.

Authors : Nicolas ONOFRIO
Affiliations : Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR

Resume : Resistive random access memory (ReRAM) form a novel class of non-volatile memory devices foreseen to replace the current Flash technology due to their excellent scalability and low power consumption. The operation of ReRAM is based on the change of resistance-state of the memory element under an external bias. In electrochemical metallization (ECM) cell, resistance switching occurs from the formation and dissolution of a metallic filament inside a dielectric. Important progresses have been achieved experimentally to understand the operation of ECM cells however, there is a need to develop robust simulation models to study the atomistic mechanism of switching in details. We recently extended the charge equilibration method to incorporate externally applied electrochemical potentials and enable large-scale reactive molecular dynamics simulations of electrochemical processes. Our model, called ?EChemDID? equilibrates the electrochemical potential in connected metallic regions, including atoms dissolving from or depositing into electrodes. This equilibration process is performed using a diffusion equation and enables atomistic simulations of nanoscale electrochemical devices. In this talk, we will present EChemDID and discuss the atomic mechanism of filamentary switching, including examples based on simulations of Cu/a-SiO2 and a-GeS2 cells.

Authors : Nina Schrödl, Andreas Egger, Edith Bucher, Christian Berger, Werner Sitte
Affiliations : Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria

Resume : Poisoning of the oxygen electrode by chromium is a well-known degradation mechanism in solid oxide cells which can cause severe performance degradation over long operating times. Compared to solid oxide fuel cells (SOFCs), degradation rates of solid oxide electrolyzer cells (SOECs) are currently roughly one order of magnitude higher. The mixed ionic-electronic conducting ceramic La2NiO4+? (LNO) has been widely discussed as a more Cr-tolerant electrode material for solid oxide fuel cells as compared to alkaline-earth containing state-of-the-art materials like (La,Sr)(Fe,Co)O3-?. LNO exhibits fast oxygen diffusion, high catalytic activity for the oxygen surface exchange reaction and sufficient electronic conductivity. To improve electrode-electrolyte adhesion at high current densities, composite electrodes of LNO and gadolinia-doped ceria (GDC) were prepared and screen-printed on GDC electrolyte substrates. Current-voltage analyses and electrochemical impedance spectroscopy were performed on symmetrical cells under anodic and cathodic polarization at 800°C. In addition, the cells were exposed to a Cr-source in dry and humidified O2/Ar atmospheres. Pronounced changes in the electrode performance are observed under current load and humid conditions in the presence of chromium [1]. The observed degradation phenomena are correlated with results from post-test analysis by electron microscopy. [1] A. Egger, N. Schrödl, C. Gspan, W. Sitte, Solid State Ionics 299 (2017) 18-25.

Authors : M.V. REDDY, Stefan ADAMS
Affiliations : Department of Materials Science and Engineering, National University of Singapore

Resume : Vanadium-based oxides (LiV3O8 and V2O5) have been used as cathode material for polymer batteries due to favourable operating voltage, high capacity and safety. The objective of this study is to synthesize layered LiV3O8 and V2O5 by facile hotplate method and understand the effect of the chelating agents (citric acid, urea, polyethylene oxide, polyvinylpyrrolidone, oxalic acid and malonic acid) on the morphology, structural and electrochemical properties. Materials were evaluated by SEM, TEM, XRD, XPS and surface area techniques. Cyclic voltammetry studies show slight differences in the redox potentials with the different chelating agents as well as before and after calcination. An average discharge charge potential of 2.75V vs. Li was noted with LiV3O8, whereas V2O5 showed 2.4 V vs. Li during cathodic scan and multiple redox peaks at 3.4V vs. Li during anodic scan. Galvanostatic cycling shows stable reversible capacities in the range 220 to 250 mAh/g, the highest among samples produced by citric acid assisted processing. On the other hand V2O5 showed a reversible capacity of 190-315 mAh g-1. Finally we will discuss in situ impedance spectroscopy and in situ XRD studies at various voltages and as a function of cycle number to understand the electrode kinetics (surface film formation, charge transfer and bulk resistance) and structural phase transformations in multi redox layered cathodes

Authors : A. Fernández-Rodríguez, J.C. González-Rosillo, X. Granados, M. Coll, X. Obradors, T. Puig, N. Mestres, A. Palau
Affiliations : Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Barcelona) Spain

Resume : A unique feature of high temperature superconductors is that their properties strongly depend on their carrier concentration. In cuprates, a reversible modulation of the carrier density can be produced by means of electric field pulses, inducing a ?Resistive Switching (RS) effect? to eventually achieve a metal insulating transition (MIT). The mechanism underlying the RS effect in these materials is still unclear though oxygen vacancies certainly play a key role. Oxygen ex-corporation/incorporation in the system imply a variation of the charge carriers and accordingly a valence change in the transition metal 3d band. We present studies on the bipolar RS effect in YBa2Cu3O7 superconducting thin films evaluated by hysteretic I(V) curves measured on micrometric metal electrodes. Temperature dependent transport and resistance measurements together with micro-Raman experiments were performed to evaluate the local oxygen diffusion through the material in different electrode configurations. In particular, the implication of the intrinsic anisotropic oxygen diffusion in cuprates has been studied experimentally and corroborated with simulation. We demonstrate that non-volatile volume phase transitions can be induced to generate transistor-like devices with free-resistance channels in which the electric field magnitude and direction, temperature, and anisotropic oxygen mobility determine their characteristics.

Authors : Alexander G. Squires, Alison Walker, Benjamin J. Morgan
Affiliations : Department of Chemistry, University of Bath, Bath, BA2 7AX; Department of Physics, University of Bath, Bath, BA2 7AY; Department of Chemistry, University of Bath, Bath, BA2 7AX

Resume : Li-ion conducting garnets have shown promise as chemically stable solid-state Li electrolytes for all solid-state Li-ion battery technologies even at room temperature. One such garnet is Li7La3Zr2O12 (LLZO) with reported Li conductivities of ~10-3 S cm-1. Stabilisation of the high temperature cubic phase of LLZO relative to the ground state tetragonal phase (Li conductivity of 1.63 x 10-6 S cm-1) is important in obtaining a highly conductive electrolyte. While studies have been carried out on the feasibility of Li vacancies and interstitials in this material, it has been suggested that O vacancies must be considered when examining the defect structure of LLZO. By elastically deforming the LLZO lattice, O vacancies can impact phase formation and stabilisation. Such deformations can also affect the migration barriers and conduction paths of Li+ in LLZO. Also of interest is the degradation of the LLZO owing to H/Li exchange during synthesis, followed by subsequent reaction when exposed to atmospheric CO2. If the conditions under which this exchange readily takes place can be understood, then it can be minimised during synthesis. In this work, we have calculated charge-dependent formation energies for Li interstitials and vacancies, O vacancies, and interstitial H in LLZO using DFT, alongside defect concentrations to understand the theoretical basis for the experimental observations discussed, and to aid in the design of synthesis conditions to minimise degradation of LLZO.

Authors : S.N. Marshenya,a B.V. Politov - a, A.Yu. Suntsov - a, I.A. Leonidov - a, S.A. Petrova - b, M.V. Patrakeev - a, V.L. Kozhevnikov - a
Affiliations : a - Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russian Federation; b - Institute of Metallurgy UB RAS, Yekaterinburg, Russian Federation.

Resume : The layered cobaltites LnBaCo2O6??, have attracted considerable interest as materials for the using as cathodes in IT SOFCs, oxygen semi-permeable membranes, catalysts, oxygen sensors, etc. Still, such drawbacks as large thermal expansion coefficient (TEC) values and insufficient stability toward reduction greatly impair the utility of the cobaltites. The efficient means of circumventing the noted deficiencies can be associated with the properties tuning via partial replacement of cobalt with other metals. In the present work aluminum is selected as a doping element because of the excellent stability of the aluminum oxide at heating and low pressures of oxygen and near equality of Al3+ and Co3+ ionic radii in octahedral coordination. The single phase oxides PrBaCo2?xAlxO6?d are obtained via combustion of glycerol-nitrate organo-metallic precursors. The aluminum doping occurs favorable for mitigation of thermal expansion and stabilization of the tetragonal structure in a wide range of temperature changes. The variations of equilibrium oxygen content in oxides are measured with a coulometric titration technique, and analyzed in terms of defect chemistry. It is shown that aluminum incorporation is accompanied by formation of rigid AlO6 octahedra in the crystal structure and enhanced disproportionation of Co3+ cations. The developed defect model is successfully applied in order to explain the data for conductivity and thermopower. The structural stability, moderate thermal expansion and high conductivity represent an advantageous properties combination for the using of PrBaCo1.9Al0.1O6?d cobaltite in various high-temperature solid state electrochemical devices.

Authors : Fei Zeng , Siheng Lu, Xiaojun Li, Jiating Chiang, Wenshuai Dong, Yuandong Hu, Jialu Liu
Affiliations : (1) Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, (2) Center for Brain Inspired Computing Research (CBICR), Tsinghua University, Beijing

Resume : It is of great interests for scientists to find systems with behaviors including signal handling, memory approximating those in neural cells and network. Recent studies have found that responses to electrical stimulations in organic semiconductors and/or electrolytes heterogeneous junctions possess features in common with synaptic plasticity in neural network. Frequency selectivity and learning were realized with dependence on the types of ions and polymer/electrolyte interfaces. In a Pt/P3HT/PEO+X+ (X=Li, Mg, Nd)/Pt hetero junction. The system response was depressed to low-frequency stimulations (10~50 Hz) but was potentiated to high-frequency stimulations (higher than 80 Hz). Long term memory and learning was realized when the semiconducting polymer was changed to MEH-PPV. Conventional spike-rate-dependent plasticity (SRDP), i.e., BCM learning rule, was realized. The microstructures suitable for frequency selectivity were examined and confirmed by SEM images. It was found that input frequency could modulate ionic doping, de-doping and re-doping at the semiconducting polymer/electrolyte interface. In the aspects of ionic kinetics, we firstly established a random channel model to describe dynamic processes at the semiconducting polymer/electrolyte interface and explain the observed learning phenomena. Subsequently, we established plasma-like transportation equetion to successfully explain ionic kinetics in ion-doped electrolyte and fit the weight modifications. We also constructed a facilitation (F) - depression (D) interplay model corresponding to ionic polarization and doping interplay at the electrolyte/semiconducting polymer interface to successfully mimic the weight modification of the post-synaptic current. The simulation results showed that the observed synaptic plasticity was caused by the great disparity between the recovery time constants of F and D (?_F and ??). Thus, we can care about to using these elements to explore possible computation protocols. Spatial summation of short-term plasticity was then studied using a pair of such junctions, i.e., Pt/Mg-doped polyethylene oxide (PEO)/Pt and Pt/Mg-doped PEO/poly(3-hexylthiophene-2,5-diyl) (P3HT)/Pt devices. The former displayed short-term depression for charging peaks and short-term facilitate (STF) for discharging peaks, while the latter displayed STF for both the charging and discharging peaks. A simple integration of parallel connection showed that the system displayed frequency selectivity in the weight modification of the charging peaks, i.e., it facilitated below a frequency threshold but depressed at a higher frequency. The frequency threshold varied with input numbers from about 60 Hz to 100 Hz. In contrast, only STF was observed in the weight modifications of the discharging peaks. In addition, the weight modification could be linearly summed from those of the two source devices though the absolute peak currents could not. Our study demonstrates that synaptic computation are feasible for parallel connection system, depending on both input frequency and linear summation of weight modifications. Finally, we suggest that directional selectivity might be realized using the parallel system.

Authors : Thuy Linh Pham, Tran Thi Huyen Tran, Hang T. T. Le, Jinju Song, Chan-Jin Park, Jaekook Kim, Jong-Sook Lee
Affiliations : Chonnam National University

Resume : Olivine lithium iron phosphate LiFePO4 has been considered as one of the most promising cathode candidates of lithium ion batteries for applications in electric vehicles and large-scale energy storage, due to its inherent merits such as high theoretical capacity (170 mAh g-1), long cyclability, high safety, low toxicity, and possibly low cost. Carbon coating, super valence ion doping in the Li-site, and nano networking of metal-rich phosphides forming at high temperature have been applied to overcome poor electronic conductivity. However, the electronic and ionic transport properties have not been fully clarified. The mixed conduction can be characterized by Hebb-Wagner method using selectively blocking electrodes. From the polarization and depolarization relaxation diffusion kinetics as well as transport numbers can be obtained. Equivalent frequency domain response may be more advantageous in the experimental and analyzing practice. In this work the optimized sintering condition for polycrystalline LiFePO4 samples was found to prepare dense samples for the electrochemical cells. Two electrode configurations were made: Ag paste for the ion-blocking electrodes and liquid electrolyte (1M LiPF6 in EC/DMC = 1/1 vol.% with 10 vol.% FEC) held by separators between lithium foils and the sample as electron-blocking electrodes. Comparison of frequency and temperature dependence of two cells can give insights into the mixed-ionic-electronic conduction behavior in LiFePO4 which is directly related to the chemical diffusion governing charging-discharging kinetics.

Authors : Ailbhe L. Gavin, Graeme W. Watson
Affiliations : School of Chemistry and CRANN, Trinity College Dublin, Dublin 2, Ireland

Resume : Sr-doped pseudocubic LaMnO3 has been widely studied as the cathode for high temperature solid oxide fuel cells. Below 750K, there is a phase change to the orthorhombic structure. Introduction of lower valence dopant cations at both the La and Mn sites can improve the ionic and electronic conductivity of orthorhombic LaMnO3 for intermediate termperature solid oxide fuel cells. Ruddlesden-Popper materials, An+1BnO3n+1, have shown promise as mixed ionic and electronic conducting cathodes. They consist of n ABO3 perovskite layers, which can accommodate oxygen vacancies, separated by AO rocksalt layers, which can accommodate oxygen interstitials. La2NiO4 is one such material, and has attracted interest due to good conductivity in the required temperature range, and compatibility with ceria-based electrolytes. The formation energies of defects in orthorhombic LaMnO3 and La2NiO4 have been calculated using PBEsol+U. Oxygen defect formation in LaMnO3 and La2NiO4, and their dependence on temperature and oxygen partial pressure, in the bulk and at the low index surfaces has been examined. The formation energies of charged isolated defects and clustered defect pairs have been calculated, by placing defects at either the La or Mn(Ni) site (Mg, Ca, Sr and Ba (LaMnO3) and Sr and Fe (La2NiO4)) to establish the site at which they will be introduced. The charge compensation mechanism for the introduction of these dopants has been investigated, considering both ionic and electronic compensation.

Authors : Politov B.V.- a, Suntsov A.Yu.- a, Shishkin D.A.- b,c, Kellerman D.G.- a, Kozhevnikov V.L.- a
Affiliations : a - Institute of solid state chemistry, UB RAS, Yekaterinburg, Russia; b - Institute of metal physics, UB RAS, Yekaterinburg, Russia; c - Ural Federal University, Yekaterinburg, Russia;

Resume : Solid oxides with double perovskite structure RBaCo2O6 where R ? rare earth metal attract considerable attention nowadays due to a number of unique properties which allow these materials to be applied in various electrochemical and magnetic devices. Recently it was shown that at both high and low temperatures RBaCo2O6 cobaltites possess sufficient values of electron conductivity although there is no complete understanding of the processes governing such phenomenon. Complexity of the problem is linked mostly with a variety of cobalt ions? oxidation and spin states along with RBaCo2O6-? wide oxygen homogeneity range. Magnetic properties of these compounds also unobviously depend on oxygen content, that?s why more studies are needed for establishing complete theoretical model of electron transport in perovskite-like cobaltites. In accordance with the problems mentioned, solid solutions of nominal composition PrBaCo2-xNixO6?? (x = 0, 0.2) were synthesized; their phase purity was confirmed by XRD analysis. Magnetic properties of samples with x = 0 and x = 0.2 were studied in high temperature and low temperature conditions. Electrical conductivity and thermopower for both specimens were measured in different thermal and pressure conditions. Correlations between structural, transport and magnetic characteristics were established.

Authors : B. Meunier1, D. Pla1, R. Rodriguez-Lamas1, M. Boudard1, O. Renault2, E. Martinez2, N. Chevalier2, C.Jiménez1, M. Burriel1
Affiliations : 1. Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France 2. Univ. Grenoble Alpes, LETI, CEA, Minatec Campus, Grenoble, France

Resume : Resistive switching (RS) is currently one of the hot topics in the frontier between microelectronics and materials science. In particular, Resistive Random Access Memories are one of the most promising alternatives beyond Flash memories. In this work we present RS-based devices using a LaMnO3 d (LMO) thin layer as active material. The resistance of this LMO-based heterostructure can be switched between high and low resistance states by applying an external electric field. Two main RS mechanisms have been reported for valence change memories: filamentary and interfacial. In particular, for the LMO-based heterostructures prepared, we have observed both filamentary and interfacial behavior, depending on the MOCVD deposition conditions and on the electrical measurement configuration used. Using c-AFM, we succeeded to achieve local RS as well as large area RS (over a region of several hundreds of micrometers). Thereby,surface analysis by photoemission spectroscopy was carried out on regions which had been set to different resistance states. We propose a mechanism for RS based on the interpretation of lanthanum and manganese photoemission spectra for the different regions. What is more, complementary to the ex-situ characterization, operando HAXPES measurements during electrical RS have been performed using synchrotron light sources (SOLEIL and Spring-8). They bring crucial information regarding the key role of the electrode/LMO interface

Authors : Sarunas Bagdzevicius1, Michel Boudard1, José M. Caicedo2, X. Mescot3, Raquel Rodríguez-Lamas1,2, José Santiso2 and Mónica Burriel1
Affiliations : 1Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France 2Institut Catala de Nanociencia i Nanotecnologia (ICN2), Bellaterra, Barcelona 08193, Spain 3Univ. Grenoble Alpes, CNRS, Grenoble INP, IMEP-LAHC, F-38000 Grenoble, France

Resume : Resistive switching (RS) research exploded recently when it was established as one of the promising pathways for ?beyond CMOS? emerging memory devices. Two terminal Resistive Random Access Memories (ReRAMs) have very attractive information storage density (4F2) and sub pJ/bit energy efficiency. In this work we have investigated the resistive switching behavior of a heterostructure using a double-perovskite oxide with high oxygen mobility, namely GdBaCo2O5 ? (GBCO). At room temperature non-volatile bipolar RS can be induced in Ag/GBCO/LaNiO3 heterostructures both by voltage sweeps and by pulsed measurements. The nature of the observed non-linear conduction mechanism, as well as the area-dependence of the switching will be discussed. In addition, devices set in different resistive states (HRS and LRS) were investigated at low temperature measurements down to 20 K. These measurements, together with I(V) curves at low temperatures, revealed that the RS can be suppressed by the magnetic phase transition (at 180 K) and reappears at lower temperatures. These results lead to a completely new and promising way to control RS in valence change memories by the magnetic phase transition modulation.

Authors : M. Kazar Mendes 1*, E. Martinez 1, J.M. Ablett 2, R. Gassilloud 1, M. Bernard 1, O. Renault 1, J. P. Rueff 23, N. Barrett 4
Affiliations : 1 Univ. Grenoble Alpes, F-38000 Grenoble, France CEA, LETI, MINATEC Campus, F-38054 Grenoble, France ; 2 Synchrotron SOLEIL, l?Orme des Merisiers, Saint-Aubin, F-91192 Gif-sur-Yvette Cedex, France; 3 Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris Cedex 05, France; 4 SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France

Resume : Conductive-bridge random access memories (CBRAM) are emerging non-volatile memories. The mechanism is related to ionic transport and electrochemical reactions, which give rise to the formation and dissolution of a conductive filament through the insulating dielectric layer. Data storage relies on switching the resistivity between two high and low resistance states by applying voltage or current pulses. We investigate the electrochemical reactions involved in the switching mechanism of Te-based CBRAMs. We have used hard X-ray photoelectron spectroscopy (at the Galaxies beamline - Soleil) to learn about electrochemical reactions involved in the resistive switching. The comparison between the different resistance states shows the role of the electrode/electrolyte interfaces. For the TiN/ZrTe/Al2O3/Ta stack, results highlight the reduction of Zr together with alumina oxidation after reverse forming. The sample polarization causes oxygen migration, probably in the O2- form, pushed by the upper negative bias towards the Ta electrode. When reversing the polarity of the applied voltage (Reset operation), we observe Zr reoxidation and alumina reduction, characterizing oxygen migration towards the ZrTe electrode. Taking into account the important role of oxygen migration in the filament formation/dissolution, we also discuss results obtained by XPS with in-situ electrical polarization (under ultra-vacuum) to better understand the role of the surface oxidation in the resistive switching.

Authors : Lucile Bernadet (1), Elba Hernández (1), Isabel Guevara (1), Carlos Moncasi (1), Alex Morata (1), Marc Torrell (1), Albert Tarancón (1)(2)
Affiliations : (1) Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy, Jardins de les Dones de Negre 1, 2nd Floor, 08930, Sant Adria de Besos, Barcelona, Spain (2) ICREA, Passeig Luis Companys 23, 08010, Barcelona, Spain

Resume : Solid Oxide Electrolysis Cells (SOEC) are one of the most efficient proposed technologies for chemical energy storage. However, electrodes stability under high production rates and dynamic operation is one main issue for their long term operation. The aim of the work was to define dynamic operation SOEC conditions that can lead to maximize durability of fuel electrode supported cells and for electrolyte supported symmetric cells. State of the art and symmetric materials have been used as oxygen and fuel electrode to optimize the stability of the SOEC. Two different types of cells are presented in this work. A first set of fuel supported electrode cells based on Ni-YSZ with La0.6Sr0.4Co0.2Fe0.8O3-? (LSCF) infiltrating CGO nanostructured scaffold as oxygen electrode were studied. After a first structural and electrochemical characterization in electrolysis and co-electrolysis modes, the cells showed up to 1 at 1.3 V and a degradation of < 2 obtained by 800 h test. Those good results led to apply more severe conditions like higher fuel utilization, exothermal modes or dynamic current profile. The second set of cells was composed by electrolyte supported cells made with symmetric electrodes (SFM or LSCM) which can operate as fuel or oxygen electrode. Maximization of the durability has been attempted by reversible operation or interchanging the atmospheres. Post-mortem characterization was then carried out by SEM-EDX.

Authors : F. Chiabrera (1), A. Hornés (1), I. Garbayo (1), Alejandro Morata (1), Albert Tarancón (1)(2)
Affiliations : (1) Department of Advanced Materials for Energy, Catalonia Institute for Energy Research (IREC), Jardí de les Dones de Negre 1, Sant Adrià de Besòs, 08930 , Spain; (2) Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís Companys 23, 08010, Barcelona, Spain;

Resume : Lanthanum-based perovskites with general formula La0.8Sr0.2MO3±? (M = Co, Mn, Fe) have been extensively used as oxygen electrodes in solid oxide fuel cells (SOFC). However, issues related with low ionic conductivity, low stability and/or incompatibility with other fuel cell components have typically limited their broad implementation. A promising approach to overcome these inconveniences has been the combination of different elements in the M site, looking for the optimum mixed properties. In this sense, this work presents a high-throughput methodology for the preparation of compositional maps of La0.8Sr0.2MO3±? by combinatorial Pulsed Laser Deposition. Many efforts and resources are usually dedicated to search for the optimum composition of a material for certain application. Opposed to that, this technique allows the fabrication of thin films with multiple compositions in a single experiment. Alternating ablation of different parent compound targets together with rotation of the substrate allows the deposition of layers with a complete and precise chemical composition distribution. This work comprises the fabrication and extensive characterization of combinatorial thin films of La0.8Sr0.2MnO3±?, La0.8Sr0.2FeO3±? and La0.8Sr0.2CoO3±?. The compositional and structural properties will be presented, and correlated with the electrochemical properties, with the final goal of selecting the optimum composition for its use as oxygen electrode in SOFC.

Authors : Firman Mangasa Simanjuntak, Takeo Ohno, Seiji Samukawa
Affiliations : WPI-Advanced Institute for Materials Research, Tohoku University, Japan; WPI-Advanced Institute for Materials Research, Tohoku University, Japan; WPI-Advanced Institute for Materials Research, Tohoku University, Japan and Institute of Fluid Science, Tohoku University, Japan;

Resume : Conducting bridge random access memory (CBRAM) is one of the emerging memory technologies that shows good potential for the future universal data storage. The memory performance of the CBRAM is significantly determined by the properties of the storage layer. Among other various oxides, the use of ZnO material as the storage layer for CBRAM is often overlooked. Although the ZnO has many advantages for mass fabrication (cheap material, environment-friendly, chemically stable and easily synthesized at a low temperature), the n-type nature of the ZnO may lead to the insufficient switching performance. There are various methods that have been reported to improve ZnO-based resistive switching characteristics. However, these techniques are complicated and time-consuming. In this work, we offer a novel approach to enhance switching behavior of the ZnO-based CBRAM by controlling the concentration of the defects in ZnO films with neutral beam oxidation (NBO) technique. It is found that no switching characteristics were observed in the control device (a device made without surface treatment). The switching behavior was observed after the ZnO films were surface-irradiated with neutral oxygen beam. However, an excessive surface treatment may lead to the deterioration of switching stability. Further electrical and materials analysis were conducted in order to explain this phenomenon.

Authors : Daniel Schumacher; Wolfgang Stein
Affiliations : SURFACE systems+technology GmbH+Co KG, Rheinstr. 7 , D-41836 Hückelhoven

Resume : Multi Process Thin Film Deposition and complex Sample Preparation Cycle under protected Atmosphere - a flexible Solution for Materials in Battery Research Daniel Schumacher, Wolfgang Stein SURFACE systems+technology GmbH+Co KG, Rheinstr. 7 , D-41836 Hückelhoven New materials or advanced functional films are always dedicated for specific aplications. Very often either the substrate material or the film material are strongly sensitive against normal environmetal conditions. Even if the components of such deposition are not sensitiv against such attac, the interfacing between substrate and film is effected from such influence. The solution in material research for such problems is an isolation of such substrate under strongly controlled atmosphere, which can be achieved with the use of glove boxes with integrated gas cleaning systems. The user interacts via isolation gloves to handle sensitive materials in the glove box wich are introduced to it via integrated load lock ports. The combination of such controlled work bench to any kind of deposition system is a problem, because normally no easy way exist to transfer such materials from a glove box into separate deposition systems. Only a fully protected connection from such glove box to the deposition system allows an undisturbed transfer. But standard deposition systems are not prepared for such transfer. SURFACE offers now fully integrated process systems which have a complete glovebox built in. In addition the complete design of such system recognizes the reduction of handling performance of the user caused by the thick gloves and its limited taktile sensitivities. Any services on such deposition system is generated from the atmosphere side, without disturbing the conditions of the contolled atmoshere in the glove box. The fully integrated style of the glove box reduces also the necessary floor space of such comlete set-up in the lab. As an excample : the total foot print of a complet PLD Glove Box system including big Excimer laser, its gas cabinet, the process automation system with user interface, the vacuum chamber, cooling chiller and the gas control cabinet fits to a floor space of 2,5m x 0,8m and includes already the glove box workstation with a working width of 1 to 1,5 m. Exambles for such integrated systems are presented.

Authors : Mandvi Saxena, Tanmoy Maiti
Affiliations : Plasmonics and Perovskites Laboratory, Department of Materials Science and Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh, India 208016

Resume : Recently double perovskites (A2B/B//O6) have been investigated as thermoelectric materials due to good combination of high Seebeck coefficient, good electrical conductivity and low thermal conductivity. In general, double perovskite materials show high Seebeck coefficient, however they suffer from low electrical conductivity. Electrical conductivity of these materials needs to be improved to develop efficient thermoelectric devices. In the present work, environment friendly, non-toxic double perovskites AxSr2-xTiMoO6 (A=Ba, La) have been synthesized by solid-state reaction process. Sintering of these ceramics has been done under reducing atmosphere to obtain single phase compound. The electrical conductivity and Seebeck coefficient were simultaneously measured from room temperature to 1273 K. High electrical conductivity (105 S/m) has been found. Thermopower (S) measurement confirmed the conductivity switching from p-type to n-type behaviour at higher temperature. To evaluate the source of charge carries and oxidation states of cations in these ceramics, XPS measurement has been carried out. Conductivity mechanism of these double perovskites has been found to be governed by small polaron hopping model. Temperature dependent Seebeck coefficient has been explained using an analytical model for coexistence of low mobility oxygen vacancies and high mobility electrons in these oxides.

Authors : Stevin S. Pramana,1* Tom Baikie,2 Tim White3
Affiliations : 1School of Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom 2Energy Research Institute at Nanyang Technological University, Singapore 3School of Materials Science and Engineering, Nanyang Technological University, Singapore

Resume : Apatite ceramics are highly adaptive to various substitutions and technologically important as bone replacements, catalysts, for radioactive waste remediation and candidate intermediate temperature solid oxide fuel cell (SOFC) electrolytes. They are crystallochemically described as A10(BO4)6X2 where A and B are larger and smaller cations, respectively and X is an anion.1 Oxygen ion conduction in apatites via interstitials and/or vacancies was presumably considered as one-dimensional conduction along [001].2 However, it could not account for the significant conduction perpendicular to [001] in the Pr,Nd,Sm9.33(SiO4)6O2 single crystals.3 Analyzing powder neutron diffraction of stoichiometric La10Ge6O27, the interstitial oxygen was determined to be located in between two GeO4 tetrahedra, describing this compound to be La10(GeO4)5(GeO5)O2 rather than La10(GeO4)6O3. In addition, the inter-tunnel oxygen migration mechanism in apatites was proposed via an interstitial hopping between GeO4-GeO5 species. These findings modify the taxonomy of general apatite crystallography family to possible hybrid A10[(BO3/BO4/BO5)6][X2] genus beside the single neutral, oxidized and reduced ones which can be engineered for improved performance. Lattice parameter and interaxial angle trends derived from Rietveld refinement of in-situ high temperature powder neutron diffraction data demonstrated that this compound undergoes polymorphic transformations (P-1 (T < 700°C) -> P21/m (700 < T < 800°C) -> P63/m (T > 800°C)) in consistent with the ionic conductivity. Furthermore, altervalent dopants (La3+ + 1/2O2- -> AE2+ ; AE = Ca, Sr, Ba) were introduced to optimise the conductivity and study the pseudomorphic transformations from P-1 to P63/m by high resolution synchrotron powder diffraction, extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM). It is concluded that BO5 motif is important in tailoring highly conducting apatite electrolytes. 1T. White, C. Ferraris, J. Kim & S. Madhavi, in Reviews in Mineralogy and Geochemistry, vol. 57, 307 (2005). 2J. R. Tolchard, M. S. Islam & P. R. Slater, J. Mater. Chem., 13, 1956 (2003). 3S. Nakayama & M. Higuchi, J. Mater. Sci. Lett., 20, 913 (2001).

Authors : Yulia Mateyshina1,3*, Dmitriy Alekseev3, Artem Ulihin1, Nikolai Uvarov1,2,3
Affiliations : Institute of Solid State Chemistry and Mechanochemistry SB RAS, Russia; Novosibirsk State Technical University, Russia; Novosibirsk State University, Russia

Resume : Previously, when investigating the transport properties of alkali metal nitrites, unusual results were obtained for cesium nitrite, which exhibited rather high conductivity in the range of 5 *10-8 S / cm at 25 ° C to 10-3 S / cm at 350 ° C [1-2]. It was shown that the conductivity of CsNO2 is ionic, and the most probable type of ion transfer mechanism is the migration of cationic vacancies [2]. In this work we present the results of the experimental study of physical and transport properties of composite solid electrolytes based on CsNO2. Solid composite electrolytes CsNO2 - A (A= Al2O3, MgO, Cnd) have been synthesized by mixing of preliminary dehydrated components followed by sintering at 390oC. It was shown that the conductivity of composites goes through a maximum with the highest conductivity, 10-1-10-3 S/cm at 352¢C. Inorganic solid electrolytes are mechanically and thermally stable and thus may be regarded as the most promising electrolytes for the development of solid-state electrochemical devices. In this work all-solid-state supercapacitors with the carbon electrodes (Ss>1000 m2/g) and the composite solid electrolytes with high conductivity were assembled and investigated. The cells were prepared by hot-pressing and electrochemically tested. References [1] H. Honda, M. Kenmotsu, N. Onoda-Yamamuro, H. Ohki, S. Ishimaru, R. Ikeda, Y. Furukawa. Z. Naturforsch, 51a (1996) p. 761-p.768. [2] Yu. Mateyshina, N. Uvarov. Solid State Ionics, (2017) V. 302, p.77-82.

Authors : Federico Baiutti,[a] Simone Anelli,[a] Elba Hernandez,[a] Alex Morata,[a] Marc Torrell,[a] Albert Tarancon [a,b]
Affiliations : [a] Institut de Recerca en Energia de Catalunya (IREC), Jardins de les Dones de Negre 1, 08930, Sant Adrià de Besòs, Barcelona, SPAIN; [b] ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain

Resume : Mesoporous cerium oxide, which possesses ordered pore structure in the nm-range and maximized surface area (BET area up to 120 m2/g), presents relevant technological importance in the field of oxide fuel cells and electrolyzers due to their thermal stability which makes them a good candidate for use as nanostructured electrodes upon infiltration with a catalytically active component (e.g. LSM, LSC), as recently shown.1,2 In this work, results on the investigation of the fundamental electrochemical properties of mesoporous doped ceria (Ce2-xAxO2, A=Pr, Gd) are presented. A number of structural and functional characterization techniques have been employed (including XRD, nitrogen physisorption, electron microscopy, electrochemical impedance spectroscopy of symmetric cells), which allowed us to relate the electrical properties with the local structural parameters, such as porosity, degree of sintering, presence of secondary phase impurities. These points are critically addressed and we evaluate the possibilities of improving the material properties not only by means of processing optimization, but also by chemistry engineering, e.g. by the use of sintering aids and by an appropriate choice of the chemical composition, which promotes the material catalytic activity.

Authors : Savitha Thayumanasundaram a*, Vijay Shankar Rangasamy a, Jin Won Seo b, Jean-Pierre Locquet a
Affiliations : a Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium b Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44 - bus 2450, B-3001 Leuven, Belgium

Resume : Li2MSiO4 (M=Co,Fe,Mn) is a promising candidate for cathode materials for Lithium ion batteries due of its high theoretical capacity ~ 300 mAh/g. Among these, Li2CoSiO4 (LCS) suffers from severe structural stability problems during electrochemical cycling when compared to Li2FeSiO4 and Li2MnSiO4. After the first charging of LCS, there is an unfavorable structural rearrangement which leads to drastic capacity fading. In this study, we have partially substituted lithium with sodium in small amount such as 10% and 20% to investigate if the difference in the atomic size of these two alkali atoms helps to stabilize the structure during cycling. LCS, 10% Na doped LCS (LNCS), 20% Na doped LCS (LN2CS) and Multi-Walled Carbon Nanotube (MWCNT) doped LNCS (LNCS-CNT) were prepared by sol-gel and thermal, structural analysis were performed. The changes in the morphological features due to the Na addition and the formation of conductive network by MWCNT doping in LNCS are analyzed by SEM. Cyclic voltammetry shows better reversibility in LNCS than LCS in the voltage region 3.5 to 4.7 V. The capacity of LNCS in the second cycle is ~ 130 mAh/g which is higher than in LCS (30 mAh/g). LNCS-CNT delivers a capacity of about 180 mAh/g which is the highest ever capacity reported for LCS after 30 cycles. Thus, Na doping in LCS has enhanced reversible capacity and rate capability due to the increase in lattice volume and also stable structure during cycling.

Authors : Vijay Shankar Rangasamy*, Savitha Thayumanasundaram, Jean-Pierre Locquet
Affiliations : Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium

Resume : We report the preparation of a polymer electrolyte using poly (vinyl alcohol) (PVA) as the polymer network and an ionic liquid (IL) solution based on piperidinium cation (PMP) as the lithium source. Various molar concentrations of the lithium bis(trifluoromethansulfonyl)imide (LiTFSI) salt were added to the IL. Polymer membranes were prepared by adding these ionic liquid solutions to PVA by solvent casting technique. The glass transition temperature of PVA decreases with the addition of IL confirming that the IL acts as a plasticizer leading to an increase in ionic conductivity. The maximum conductivity was observed for the membrane with 0.6m PMPTFSI-LiTFSI (3 mS cm-1) and could be correlated to its low viscosity value. Tan delta (from dynamic mechanical analysis) of IL doped samples show broader relaxation peak than pure PVA. Vinylene carbonate (VC) was added as an additive to stabilize the SEI layer during electrochemical cycling. Cyclic voltammetry of the polymer electrolytes confirms the reversible redox process (lithium stripping and deposition) and linear sweep voltammetry confirms that these electrolytes are stable up to 4.7 V. Galvanostatic charge-discharge studies of the polymer electrolytes in lithium half-cells with LiFePO4 (LFP) cathode delivered a capacity of 180 mAh g?1 at 60 °C. Li diffusion coefficient was calculated to be in the order of 10?15 cm2 s?1 using electrochemical impedance spectroscopy (EIS).

Authors : Federico Baiutti,[a] Matias Acosta,[b] Iñigo Garbayo,[a] Nerea Alayo,[a] Francesco Chiabrera,[a] Alex Morata,[a] Judith L. MacManus-Driscoll,[b] Albert Tarancón [a,c]
Affiliations : [a] Institut de Recerca en Energia de Catalunya (IREC), Jardins de les Dones de Negre 1, 08930, Sant Adrià de Besòs, Barcelona, SPAIN; [b] Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, CB3 0FS, Cambridge, UK; [c] ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain

Resume : Microdevices for energy transformation such as micro-solid oxide fuel cells or micro-gas sensors represent a very promising technology for portable applications, being able to meet the demands of system miniaturization, lower operating temperature and fast response. Although effort has been put in recent years towards the development of such type of devices,[1] the classical Si-based architecture suffers from limitations related e.g. to instabilities at high temperatures. Here we present a study aimed to the development of a new-generation device based on highly crystalline ceramic layers and thin-film engineering. The core of the structure is a YSZ film (?200 nm thick) deposited directly on Si by large-area PLD. We show that the film crystal structure and elastic strain can be tuned by changing the process parameters and that such a layer can be employed as a platform for the integration of nanostructured ceramic electrodes with superior thermal stability and optimized microstructure. In particular, we explore the possibility of employing artificial MIECs based on vertically aligned nanopillars. Such an approach does not only represent a step towards the realization of systems with improved performance, but also opens up opportunities for the technological implementation of nano-engineered oxide films and for fundamental studies on oxide heterostructures. [1] I. Garbayo et al., Energy Environ. Sci., 2014, 7

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Advanced Characterization Techniques : Roger A. De Souza and Christian Jooss
Authors : David Diercks, Brian Gorman
Affiliations : Colorado School of Mines, Colorado School of Mines

Resume : Oxide materials play a prominent role in emerging and evolving advanced functional materials applications such as batteries, fuel cells, sensors, and separation membranes. A major limitation is that cost-effective production methods of most oxides result in polycrystalline materials. The resulting grain boundary (GB) regions can differ substantially from the bulk material both in composition and structure. This is further complicated by the localized charges of oxide bonds, leading to local variations in charge while still requiring the preservation of electroneutrality globally. The end result can include vastly different properties at the GBs than in the interiors of the crystals, often reducing performance. Also, GBs are not homogeneous. While valuable information has been learned through studies of artificially produced periodic two-dimensional GBs, the materials used in actual applications predominantly have three-dimensional, random high-angle GBs. Therefore, the quantitative characterization of the 3-D GB nature is indispensable for the understanding and development of advanced functional materials. Several analytical techniques have been applied to probing some aspects related to GB composition. However, limitations have prevented the full realization of the desired 3-D characterization at the necessary size scale. The most common method in recent years is high resolution scanning transmission electron microscopy (TEM). With continued improvements in aberration-correction capabilities, this technique is unsurpassed in imaging the GB structure, particularly for well-controlled GBs and interfaces, such as bicrystals [1-4]. However, quantification in TEM using spectroscopic techniques, such as electron energy loss spectroscopy (EELS) and energy dispersive x-ray spectroscopy (EDX), can produce misleading quantification results, even for a single crystal of known composition [5]. Also complicating quantification is the low atomic mass of oxygen and its subsequently low characteristic X-ray transition energies [6-9]. Consequently, compositional GB analyses using EELS and EDX typically provide 1-D or 2-D projections of semi-quantitative information. The challenge in measuring 3-D variations, particularly in oxygen concentration, over such a small region makes atom probe tomography (APT) one of the only methods available for direct quantification. APT analyses have demonstrated the ability to identify local 3-D chemical variations in nanometer-sized structures. For example, APT has shown segregation of solutes [10-11] and impurities [12] and precipitate formation at GBs [13] in metals. More recently, APT measurements of impurity and dopant segregation at the GBs of oxide materials have been demonstrated [14-16]. In this talk, the application of APT to quantitative analysis of oxide grain and phase boundaries for a number of different functional oxide materials is presented. In particular, the ability to relate the nanoscale measurements to processing conditions and/or macro-scale properties, such as conductivity and capacity fade are discussed [17-18]. This includes the discussion of both the advantages and limitations of APT for these analyses and the opportunities for correlating APT with other characterization techniques [19]. [1] H. Hojo et al., Nano Letters, 10 (2010) p. 4668-4672. [2] Z. Wang et al., Nature, 479 (2011) p. 380-383. [3] B. Feng et al., Applied Physics Letters, 100 (2012) p. 073109. [4] K. Song et al., APL Materials, 2 (2014) p. 032104. [5] G. Kothleitner et al., Physical Review Letters, 112 (2014) p. 085501. [6] M. Aoki et al., J. Am. Ceram. Soc., 79 (1996) p. 1169-1180. [7] Y. Lei et al., J. Am. Ceram. Soc., 85 (2002) p. 2359?2363. [8] T. Nakagawa, et al., J. of Mater. Sci., 40 (2005) p. 3185-3190. [9] J. An et al., Sci. Rep., 3 (2013). [10] J. A. Horton and M. K. Miller, Acta Metall. 35 (1987) p. 133. [11] B. W. Krakauer and D. N. Seidman, Rev. Sci. Instrum. 63 (1992) p. 4071. [12] Dieter Isheim et al., Scripta Mater. 55 (2006), p. 35. [13] S.P. Ringer, K. Hono, and T. Sakurai, Metall. and Mater. Trans. A 26 (1995), p 2207. [14] Y.M. Chen et al., Scripta Mater. 61 (2009) p. 693. [15] Emmanuelle A. Marquis et al., Mater. Today 13 (2010) p. 34. [16] F. Li et al., Scripta Mater. 63 (2010) p. 332. [17] David R. Diercks et al., Journal of the electrochemical society 161 (2014) p. F3039-F3045. [18] David R. Diercks et al., Journal of Materials Chemistry A 4 (2016) p 5167-5175. [19] B. P. Gorman, et al. Microscopy Today 16 (2008) p. 42-47.

Authors : Dino Klotz
Affiliations : WPI-International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, Japan; Department of Materials Science and Engineering (DMSE), Massachusetts Institute of Technology (MIT), Cambridge, USA

Resume : Electrochemical Impedance Spectroscopy (EIS) is a widely applied tool in solid state ionics. It is used to analyze transport and adsorption processes as well as interfacial reactions for a large variety of electrochemical systems. Yet, there are elusive processes and intermediate reaction steps that cannot be identified just by analyzing the impedance of the system, defined as the transfer function between voltage and current. I will show how additional quantities can be probed in order to gain more information about processes and characteristics of the electrochemical system. Replacing voltage or current, i. e. excitation or response signal, in an EIS measurement by another physical quantity such as illumination or temperature leads to so-called generalized electrochemical impedance spectroscopy (GEIS) measurements, that open up a whole new field of measurement techniques just recently receiving interest in the materials community. Such measurements can be applied in situ and provide a general transfer function capable of being analyzed with the tools readily available for evaluating EIS data. In this talk I give an overview of GEIS measurements such as: intensity modulated photocurrent/-voltage spectroscopy (IMPS/IMVS), optical impedance spectroscopy (OIS) and electro-thermal impedance spectroscopy (ETIS). Practical examples it will be provided that demonstrate the new insights that can be gained with the aid of GEIS. An overview of experimental setups will also be provided. This work was supported by JSPS Core-to-Core Program, A. Advanced Research Networks.

Authors : Jong-Sook Lee
Affiliations : Chonnam National University

Resume : Impedance spectroscopy is currently an indispensable tool in many subjects of solid state ionics and becoming even more popular. We researchers considered to have the expertise may have to admit that the techniques appear to be dead-ended. Many experimental data remain incompletely and unsatisfactorily explained. Physical modeling of AC behavior is done by the capacitor elements as well as the resistors. While the resistor components are unambiguously defined, ideal capacitors are rarely used. A good description of real experimental data using several constant phase elements (CPEs) should not be given too much significance, since the parameters of CPEs arbitrarily adjusted have no clear physical significance and the response of the respective CPEs extends over the entire frequency range. The procedure in estimating the effective capacitance parameters from the modeling employing CPEs is not absolutely justified nor unambiguous. It is suggested that the issues have been finally substantially clarified. Firstly, Havriliak-Negami capacitance function can describe the dispersive behavior with a reason such as relaxation, trapping, etc. and also define the capacitance magnitude for physical interpretation in terms of carrier or trap concentrations and geometry factors. Secondly, diffusion-involved electrochemical responses or percolating networks can be physically modeled by transmission-lines (TL) but CPEs are employed for shunt capacitance of TLs. In fact, many electrode polarizations can be satisfactorily described by TL with the ideal shunt capacitance in the presence of an ideal Warburg interfacial impedance. The capacitance effects are thus key to understand many impedance data. Often responses with different relaxations times can be systematically described by the superposition of capacitance effects, i.e. in parallel network, rather than the series network of the resistance effects. Importantly, these models have been recently implemented in a much used commercial fitting program and thus accessible for general experimentalists. Remarkably successful applications of the new impedance spectroscopy in the description of many different solid electrolytes, solid oxide fuel cells, photoelectrochemical cells, and batteries are presented

Authors : A. Morata1, V. Siller1, F.Chiabrera1, R. Trocoli1, M. Stchakovsky2, A. Tarancón1,3
Affiliations : 1. IREC, Jardins de les Dones de Negre 1, Planta 2, 08930, Sant Adrià del Besòs, Spain; 2. HORIBA Scientific, Avenue de la Vauve, Passage Jobin Yvon, 91120 Palaiseau, France; 3. ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain

Resume : Thin film solid state batteries can play an important role in powering microdevices. Electrode materials for this application must hold high capacity, stability and be capable to discharge in a high rate. LiMn2O4 (LMO) has long been investigated as a cathode for Li-ion batteries, showing high specific charge capacity (148 mAhg?1). However, an excessive degradation rate has been reported, mainly due to Mn dissolution. Recent studies from our group have proven excellent ciclability of PLD deposited thin films of this material, showing an capacity retention of 99.996% per cycle after operating 3500 cycles at extremely high rates (348C). The understanding of the mechanisms leading to this excellent performances require of techniques capable to detect a change of the films properties during the (de-) intercalation process. Optical techniques, like Raman spectroscopy, are typically used for the in-situ study of cathode and anode materials. The use of spectroscopic ellipsometry for this purpose is much less common, despite being a powerful technique for thin film characterization. From optical constants it is possible to gain information about band gap structure and oxidation states. In this work, spectroscopic ellipsometry has been used for the first time for the in-situ study of LMO films during electrochemical cycling. The evolution of the absortion coefficient of the sample at different potentials gives insight in the lithium intercalation phenomena on this promising material.

Authors : Sebastian Schröder (1), Yongbo Wang (1), Holger Fritze (1), Thomas Defferriere (2), Harry L. Tuller (2)
Affiliations : (1) Technical University of Clausthal, IEPT, Goslar, Germany, (2) Massachusetts Institute of Technology, DMSE, Cambridge MA, USA

Resume : Oxides such as ceria and praseodymium doped ceria exhibit large deviations from stoichiometry upon exposure to reducing environments and elevated temperatures. Thin films continue to gain attention, given interests in device miniaturization and related nanoscale effects. There is growing evidence that the nonstoichiometry of thin films might differ considerably from that of bulk counterparts due to inherent stresses induced by substrate constraints and/or high surface to volume effects. Only limited means exist, however, to accurately measure oxygen nonstoichiometry in films. In this work the nonstoichiometries of pulsed laser deposited CeO2-x and Pr0.1Ce0.9O2-x (PCO) thin films are investigated by resonant nanobalances at temperatures of up to 900 °C. The devices, consisting of high-temperature stable piezoelectric resonators, enable detection of mass changes on the order of nanograms by monitoring changes in resonant frequency. The oxygen activity in the films was controlled by varying the oxygen partial pressure from 10-20 to 10-12 bar and from 10-8 to 0.1 bar for CeO2 and PCO, respectively. The nonstoichiometry was found to range from x = 10-2 to 0.1 and x = 0.02 to 0.05 for CeO2 and PCO, respectively, in good agreement with previously reported thermogravimetry and chemical capacitance studies. Means for determining absolute values for x and issues that need close attention in achieving reliable data, e.g. temperature cross sensitivity, are discussed.

Solid State Energy Devices (II): Electrolyzers : Stevin S. Pramana and Tatsumi Ishihara
Authors : Filip Podjaski 1 2, Julia Kröger 1 3, Bettina V. Lotsch 1 3 4 5
Affiliations : 1 Max Planck Institute for Solid State Research, Stuttgart, Germany; 2 Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; 3 University of Munich (LMU), Munich, Germany; 4 Nanosystems Initiative Munich (NIM), Munich, Germany; 5 Center for Nanoscience, Munich, Germany

Resume : Graphitic carbon nitrides have emerged as an earth-abundant family of polymeric materials for various photo- and electro-catalytic applications. Herein, we report a 2D cyanamide-functionalized polyheptazine imide (NCN-PHI), which for the first time enables the synergistic coupling of two key functions of energy conversion within one single material: visible light harvesting and electrochemical energy storage. We reveal the underlying mechanism of this ?solar battery? material by photo-electrochemical measurements in aqueous electrolytes, showing that the charge storage in NCN-PHI is based on the photoreduction of the carbon nitride backbone while charge compensation is realized by the adsorption of alkali metal ions within the NCN-PHI layers and at the solution interface. The photoreduced carbon nitride can thus be described as a battery anode operating as a pseudocapacitor, which can store light-induced charge in the form of long-lived, ?trapped? electrons for hours. Importantly, the potential window of this process is not limited by the water reduction reaction due to the high intrinsic overpotential of this carbon nitride for the hydrogen evolution reaction. Owing to these properties, the complexity of solar batteries is significantly reduced and higher cell voltages for aqueous batteries are possibly enabled. Thus, the feasibility of light-induced electrical energy storage and release on demand by a one-component light-charged battery anode is demonstrated, that provides a sustainable, earth abundant solution to overcome the intermittency of solar irradiation and other renewable electrical energy sources at a time. Further information can be found in: ?Dark photocatalysis: Storage of solar energy in carbon nitride for time-delayed hydrogen generation?, V.W.-h. Lau et al.,, Angew. Chem. Int. Ed. 2017, 56, 510?514 and ?Toward an Aqueous Solar Battery: Direct Electrochemical Storage of Solar Energy in Carbon Nitrides?, F. Podjaski et al., Adv. Mater. 2018, 1705477.

Authors : Teresa Andreu, Carles Ros, Sebastian Murcia-Lopez, Nina Carretero, Cristina Flox, Joan R. Morante
Affiliations : Catalonia Institute for Energy Research (IREC)

Resume : The electrical conversion and storage of solar energy is a crucial target for assuring the world energy supply in the long term. A critical parameter for the implementation of standard high-efficiency photovoltaic absorber materials for photoelectrochemical water splitting is its proper protection from chemical corrosion while remaining transparent and highly conductive. Atomic layer deposited (ALD) TiO2 layers fulfill material requirements while conformally protecting the underlying photoabsorber. Nanoscale conductivity of ALD TiO2 protective layers on silicon-based photocathodes has been analyzed, proving that the conduction path is through the columnar crystalline structure of TiO2. Because of the sluggish kinetics associated to the water oxidation reaction and of inherent limitations in the H2 economy, the possibility of storing energy to other kind of redox pairs has recently attracted more attention, giving rise to the so-called solar-powered electrochemical energy storage (SPEES), The ability of protected crystalline silicon to photoassist the V3+/V2+ cathodic reaction under simulated solar irradiation, combined with the effect of bismuth have led to important electrochemical improvements. High reversibility of the V3+/V2+ redox pair, and improvement in the electrokinetics were attained thanks to the addition of bismuth. In fact, Bi0 deposition has shown to slightly decrease the photocurrent, but the significant enhancement in the charge transfer, reflected in the overall electrochemical performance clearly justifies its use as additive in a photoassisted system for maximizing the efficiency of solar charge to battery.

Authors : Hong Zhang, Haijun Wu, Ximeng Liu, Wenjie Zang, Abdelnaby Mohamed Elshahawy, Stephen John Pennycook, Jianping Xie, Cao Guan* and John Wang*
Affiliations : Hong Zhang, Haijun Wu, Ximeng Liu, Wenjie Zang, Abdelnaby Mohamed Elshahawy, Prof. Stephen John Pennycook, Dr. Cao Guan, Prof. John Wang Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore Prof. Jianping Xie Department of Chemical and Biomolecular Engineering National University of Singapore 4 Engineering Drive 4, 117585, Singapore

Resume : Water splitting provides a clean and renewable way to produce high-purity hydrogen, but its practical application has been limited by the slow kinetics and poor stability of the electrocatalysts. Here we report a facile preparation of Pt-Co open hollow clusters embedded in carbon nanoflake arrays aligned on flexible carbon cloth (Pt-Co/C NAs, 2.5 wt% Pt), which display excellent electrocatalytic activity and ultra-long durability for both hydrogen and oxygen evolution in alkaline media. The high performance arises from the synergistic effect of the unique open hollow Pt-Co nanostructure embedded in the conductive carbon nanoflake arrays. The material can be utilized directly as a bifunctional catalyst for overall alkaline water splitting. It outperforms noble-metal-based materials in terms of much lower operation voltage (1.54 V at a current density of 10 mA cm-2) and higher stability (no degradation at constant current or voltage up to 120 h), representing a highly promising electrode for electrochemical energy conversion.

Authors : Alexander K. Opitz, Andreas Nenning, Christoph Rameshan, Markus Kubicek, Thomas Götsch, Raoul Blume, Michael Hävecker, Axel Knop-Gericke, Günther Rupprechter, Bernhard Klötzer, Jürgen Fleig
Affiliations : TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165-PC, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; University of Innsbruck, Institute of Physical Chemistry, Innrain 80-82, 6020 Innsbruck, Austria; Fritz Haber Institute of the Max Planck Society, Department of Inorganic Chemistry, Faradayweg 4-6, 14195 Berlin, Germany; Fritz Haber Institute of the Max Planck Society, Department of Inorganic Chemistry, Faradayweg 4-6, 14195 Berlin, Germany; Fritz Haber Institute of the Max Planck Society, Department of Inorganic Chemistry, Faradayweg 4-6, 14195 Berlin, Germany; TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165-PC, 1060 Vienna, Austria; University of Innsbruck, Institute of Physical Chemistry, Innrain 80-82, 6020 Innsbruck, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria;

Resume : For large scale storage of excess electrical energy CO2 electrolysis may become very important, since it offers a method of sustainable CO production, which can serve as a basis for synthesis of regenerative carbon-based fuels. CO2 reduction in solid oxide electrolysis cells (SOECs) is particularly promising, since their high operating temperature facilitates both thermodynamics and reaction kinetics. In this work, the evolution of surface chemistry of (La,Sr)FeO3-? and (La,Sr)CrO3-? based perovskite-type electrodes was studied operando by near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) during electrochemical CO2 reduction at SOEC operating temperatures. In these experiments a carbonate intermediate was identified, which only forms upon cathodic polarization. In contrast to previously studied high temperature water splitting, the CO2 electro-reduction reaction was not significantly affected by exsolved metallic particles decorating the electrode surface. Together with an analysis of polarization-induced XPS peak shifts this behavior identifies the oxide rather than the metal particles as the adsorption sites of the carbonate. Based on these observations as well as the influence of the defect chemistry of the oxide electrode on the carbonate coverage, a reaction mechanism for high temperature CO2 reduction on perovskite-type oxides is discussed.

Authors : G. E. Wilson, R. Chai, J. B. Menendez, S. S. Pramana, A. Cavallaro, S. J. Skinner, A. Aguadero
Affiliations : Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ; Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ; Department of Chemical Engineering, Imperial College London, Exhibition Road, London, SW7 2AZ; School of Engineering, University of Newcastle, Merz Court, Newcastle, NE1 7RU; Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ; Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ

Resume : Water splitting is a rising technology with the potential to enable a future hydrogen economy. Thermochemical redox reactions are one established method to produce hydrogen with a minimal carbon footprint. The current state-of-the-art redox active material, ceria, boasts fast kinetics and high cyclability. Issues however arise as high reaction temperatures are necessary. Consequently, alternative oxygen exchanging materials are being actively explored. Strontium cobalt oxides doped with antimony, molybdenum and niobium are promising materials for low temperature thermochemical water splitting due to their mixed ionic electronic conductivity. Additionally, thanks to toptactic reversible redox cycling they exhibit large oxygen storage capabilities at intermediate temperatures (480-800 °C).1-3 Thermogravimetric analysis using alternating inert and oxidising environments reveal the 5% molybdenum-doped powders to have the most encouraging reaction kinetics and expected hydrogen production up to 450 umol/g at 800 °C. Future observations by gas chromatography aim to elucidate the precise rates and hydrogen production quantities allowing a direct comparison to be made with current published materials. 1. A. Aguadero et al., Chem. Mater., 2010, 22, 789-798 2. A. Aguadero et al., Chem. Mater., 2012, 24, 2655-2663 3. V. Cascos et al., Int. J. Hy. En., 2014, 39, 14349-14354

Authors : Kuan-Ting Wu (a, b), Tatsumi Ishihara (a, b)
Affiliations : (a) Department of Applied Chemistry, Faculty of Engineering, Kyushu University, Japan (b) International Institute for Carbon-Neutral Energy Research, Kyushu University, Japan

Resume : Efficient approaches for the utilisation and management of effluent emission of CO2 are highly important subjects. Reducing CO2 emissions and converting it into useful fuels by renewable energy has been an attractive approach, using solid oxide electrolysis cells (SOECs) as a promising energy storage device. This allows effectively mitigating the increase of CO2 in the atmosphere and even producing useful fuels (e.g. H2/CO syngas and hydrocarbon source). Previously Ni-based cermet materials are usually used as fuel electrodes for SOECs. High activity and low degradation rate of the conventional cathodes is essential for the application of high-temperature electrolyser. Hence, to improve the stability, utilisation of perovskite oxides as fuel electrodes recently has been highly suggested instead of metallic-based electrodes. However, there are some critical drawbacks in perovskite materials used for the cathode in SOEC. Insufficient current density or catalytic activity limits the operation in a low- and intermediate temperature. For example, in our previous case of La(Sr)Fe(Mn)O3 cathode, an average current density of ~0.65 A/cm2 was achieved at ~1.6 V and 800°C. In addition, significant A-site segregation (SrO) is generally formed on the surface at an elevated temperature, likely leading to a certain chemical reaction (SrCO3), and consequently degradation when particularly operating in a CO2 reduced atmosphere. Therefore, we proposed to use spinel oxides, a general formula AB2O4, which are composed of two transition metals. Spinel oxides have been used in various catalytic applications (for example, decomposition of gaseous pollutants and water gas shift reaction). This type of material is expected to provide a higher current density of electrolysis and possess a mixed termination of transition metals as active roles to facilitate the reduction of CO2 and H2O. In this study, we investigate a number of spinel oxides as cathodes applied in the electrolysis of CO2 and steam co-electrolysis using LSGM as the electrolyte. Galvanostatic measurements, electrochemical impedance spectroscopy and microstructural analysis have been conducted to investigate the cell performance. In addition, the formation of the syngas CO/H2 in operation was measured by gas chromatography. It was found that one of spinel oxide, CuFe2O4, can perform promising current density values of ~1.2 A/cm2 and ~2.0 A/cm2 have been achieved in CO2/H2O and H2O electrolysis at ~1.6 V and 800°C. Also, this material shows excellent conversion efficiency of CO H2 or H2, approximately over 95% achieved. Therefore, spinel oxide may be a potential type of cathode candidates for the application of CO2/H2O and H2O electrolyser.

Authors : Si-Won Kim, Jongsup Hong, Jong-Heun Lee, Mansoo Park, Kyung Joong Yoon, Jong-Ho Lee
Affiliations : SW Kim, M. Park, K. J. Yoon, J.-H. Lee (High-temperature Energy Materials Research Center, KIST, Seoul 02792, Korea) J. Hong (Department of mechanical Engineering, Yonsei University, Seoul 03722, Korea) J. Lee (Department of Materials Science & Engineering, Korea University, Seoul 02841, Korea

Resume : High value-added synthetic gas can be produced through co-electrolysis of carbon dioxide (CO2) and water vapor (H2O) using high-temperature solid oxide cells (SOCs). However, conventional Ni-catalysts based SOC shows relatively low CO2 conversion efficiency and poor selectivity of carbon monoxide. Hence, in this study, a useful model experiment was designed to understand the exact reaction mechanism of CO2 conversion during co-electrolysis, thereby we can select the optimum catalyst for co-electrolysis cells. Thin-film type heterogeneous alloy catalysts were introduced to more clearly compare the activity of alloy catalyst with respect to its composition and effective surface area. In order to precisely control the composition and quantify the effective surface area of catalysts, thin-film and in-situ nano-alloying techniques were employed. In-situ XPS and NEXAFS analysis were carried out to investigate the composition/structural change of catalyst surface and identify the intermediate product form of catalytic reaction in real operating environment. Some computational work was also carried out to verify the reaction mechanism. In this presentation, from the fundamental understanding of CO2 conversion reaction mechanism, some candidate catalysts that can improve the CO2 conversion efficiency and the selectivity of carbon monoxide will be proposed.

Solid State Energy Devices (III): Batteries : Albert Tarancón and William Chueh
Authors : Jennifer L.M. Rupp
Affiliations : Massachusetts Institute of Technology MIT, Cambridge 02139, USA -

Resume : Next generation of energy storage and sensors may largely benefit from fast Li+ ceramic electrolyte conductors to allow for safe and efficient batteries and real-time monitoring anthropogenic CO2. Recently, Li-solid state conductors based on Li-garnet structures received attention due to their fast transfer properties and safe operation over a wide temperature range. Through this presentation basic theory and history of Li-garnets will first be introduced and critically reflected towards new device opportunities demonstrating that these electrolytes may be the start of an era to not only store energy or sense the environment but also to emulate data and information based on simple electrochemistry device architecture twists. In the first part we focus on the fundamental investigation of the electro-chemo-mechanic characteristics and design of disordered to crystallizing Li-garnet structure types and their description. Understanding the fundamental transport in solid state and asking the provokative question: how do Li-amorphous to crystalline structures conduct? As well, as how can we alter their charge-and mass transport properties for solid electrolytes and towards electrodes is discussed. Here, we firstly present new Li-garnet battery architectures for which we discuss lithium titanate and antimony electrodes in their making, electrochemistry and assembly to full battery architectures1-4. Secondly, new insights on degree of glassy to crystalline Li-garnet thin films are presented based on model experiments of the structure types. Here, the thermodynamic stability range of maximum Li-conduction, phase, nucleation and growth of nanostructure is discussed using high resolution TEM studies, near order Raman investigations on the Li-bands and electrochemical transport measurements. The insights provide novel aspects of material structure designs for both the Li-garnet structures (bulk to films) and their interfaces to electrodes, which we either functionalize to store energy for next generation solid state batteries or ... make new applications such as Li-operated CO2 sensor tracker chips. As a final part we review in a more holistic picture how one can use such materials and change the electrochemistry from energy storage, chemical sensing to data emulation for which we see prospect for electric vehicles, the Internet of Things or hardware in artificial intelligence.

Authors : Xubin Chen (a b), Knut Gandrud (a), Maarten Mees (a), Akihiko Sagara (c), Mitsuhiro Murata (c), Morio Tomiyama (c), Mikinari Shimada (c), Philippe M. Vereecken (a b)
Affiliations : (a) imec, Kapeldreef 75, B-3001, Leuven, Belgium (b) Centre for Surface Chemistry and Catalysis, KU Leuven, B-3001 Leuven, Belgium (c) Technology Innovation Division, Panasonic Corporation, 1006, Kadoma, Kadoma City, Osaka 571-8501, Japan

Resume : Solid electrolytes with Li-ion conductivity higher than 1 mS/cm are required for the development of high capacity solid-state Li-ion batteries. In the past decade, several studies were done on the improvement of ion conductivity in composite materials by employing interface enhanced ion conduction at inorganic oxide surfaces. Also, composites of oxide nanoparticles or mesoporous oxide microparticles mixed with ILE have been proposed. However, so far the ionic conductivity was always lower than that of the original ILE due to the interrupted ionic paths by percolation from particle to particle. Enhancement of the Li-ion conductivity is shown for solid nanocomposite electrolytes (SCE) based on a mesoporous silica monolith functionalized with an ionic-liquid electrolyte (ILE). The ionic conductivity of the SCE pellet exceeded that of the pure ILE liquid with over 100%, well surpassing the 1mS/cm threshold. A mechanism for enhanced ion conduction through a surface adsorbed mesophase layer is proposed.

Authors : Vladimir P. Oleshko1, William R. McGehee2, Evgheni Strelcov2,3, Saya Takeuchi4,5 Jamie Gardner2, Oleg Kirillov4, David Gundlach4, Christopher L. Soles1, Nikolai Zhitenev2, Jabez J. McClelland2
Affiliations : 1 Materials Science and Engineering Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 USA 2 Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899 USA 3 Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 USA 4 Engineering Physics Division, Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 USA 5 Theiss Research, La Jolla, CA 92037, USA

Resume : Understanding and controlling lithiation reaction pathways in Si-based anodes, such as nucleation and evolution of Li-Si phases, defect interactions, and transport of Li ions, are crucial for developing high-performance Li-ion batteries. With a theoretical capacity of ~4200 mAhg-1, which is more than 10 times greater than that of graphite, the practical use of Si anodes is, however, hampered by capacity fading and large volume changes that occur during cycling. Deeper insights into the reaction mechanisms at the atomic level are vitally needed to address this problem. In this work, we report on recent progress in studies of the lithiation of model thin film Si membranes with a low-energy focused Li-ion beam (LiFIB). The scanning LiFIB enables a Li probe size of a few tens of nm at energies ranging from 500 eV to 5 keV and beam currents up to 15 pA, allowing one to inject Li cations directly into the material with a nanoscale precision. This approach avoids electrochemical processing in electrolytes and the formation of a solid-electrolyte interface. We investigated microstructural evolution of the membranes and defects induced by Li-Si interactions vs. ion dose and characterized surface electrostatic potentials and lateral distributions of lithium in the implanted regions using spatially-correlated Kelvin probe force microscopy, HRTEM, electron diffraction, and STEM-EELS. Our findings indicate that nanoscale processes that occur at early lithiation stages involve a series of solid state transformations, including clustering of interstitials in tetragonal sites of the c-Si lattice, creation of interstitial-rich extended defects, and substantial amorphization of the Si matrix followed by the formation of various LixSi phases.

Authors : Fouad Ghamouss*a Victor Chaudoy,a Tan-Vu Huynh,b, François Tran Vana, Michaël Deschampsb
Affiliations : aLaboratoire de Physico-Chimie des Matériaux et des Electrolytes pour l?Energie (PCM2E), EA 6299, Université François Rabelais, Parc de Grandmont, 37200 Tours, France b CNRS UPR 3079 CEMHTI, Orléans University, F-45100 Orléans, France

Resume : Herein, we report, for the first time, the preparation and the characterization of an interpenetrated polymer network electrolyte (IPNE) in a thin film lithium µ-batteries (µLIBs). The IPNE was prepared by thermal free radical polymerization of methacrylate oligomers in the presence of 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (P14FSI) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) 1 The study was conducted by varying the composition of the cross-linked electrolyte (e.g. the ratio of RTIL/oligomers and LiTFSI/RTIL, the rate of cross-linking) in order to achieve an optimized composition allowing a compromise between mechanical properties, liquid confinement inside the polymer network and electrochemical performances of the quasi-solid IPNE. Lithium transference number and ionic conductivity were determined as function of the electrolyte composition and Nuclear Magnetic Resonance (NMR) spectroscopy with Pulsed Field Gradients (PFG) was used in order to measure the self-diffusion coefficients in the electrolyte. Furthermore, a thin film Lithium µ-battery was successfully constructed and cycled. The µ-battery was consisting of a stack of a thin layers of active materials (lithium anode, LCO cathode and IPNE) where the IPNE plays a role of both electrolyte and separator. The thin lithium anode (5 µm thick) was directly grown on the IPNE (5 to 10 µm thick films) by metal thermal evaporation technique leading to a compact and stable lithium/polymer electrolyte assembly which was further added to a thin LCO cathode to get the full µ-battery. After assembling, the µ-battery showed an open circuit voltage around 3 V and was cycled at different speed showing excellent capacity retention even at high speed (1C) and very promising stability (over 100 cycles). References: [1] F. Ghamouss, V. Chaudoy. E. Luais, F. Pierre, F. Tran-Van, « Microbatterie au lithium et procédé de fabrication », PCT/Fr2017/053086. Patent.

Authors : Laurent Castro (a), Marisa Falco (b), Jijeesh Ravi Nair (b?),Federico Bella (b), Fanny Bardé (a), Giuseppina Meligrana (b), Claudio Gerbaldi (b)
Affiliations : (a) Research & Development 2, Advanced Technology- Advanced Material, Toyota Motor Europe, Hoge Wei 33 B, B-1930-Zaventem, Belgium (b) GAME Lab, Department of Applied Science and Technology (DISAT), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy (?) now at Helmholtz-Institute Münster (HI MS) IEK-12: Ionics in Energy Storage, Corrensstraße 46, 48149 Münster, Germany

Resume : All solid state Li metal batteries are the most promising candidate due to their expected high energy density for next electrical vehicles (EV-HEV) generation. Among possible candidate materials for solid electrolyte, the oxide ceramic super lithium ion conductors, garnet-type Li7La3Zr2O12 (LLZO) has recently attracted much attention because of its relatively high ionic conductivity at room temperature (>10-4 S cm?1), negligible electronic conductivity and absence of harmful decomposition products upon contact with atmospheric moisture. Anyway, processing LLZO in pellets by sintering, results in brittle and more or less porous electrolytes, which often display poor interfacial contact with Li metal electrodes. Moreover, there are some reports of lithium dendrite growth and instability towards the cathode material - especially while processing of the electrode at high temperature - referred to cells assembled with this electrolyte family [1,2]. To circumvent these problems, recent efforts have been dedicated to the formulation of composite hybrid polymer electrolytes (CPEs), where the ceramic material is embedded in a polymeric matrix. As compared to the pristine components, CPEs are stiff while preserving flexibility, are easily processed, and can be conceived to attain improved ionic conductivity and interfacial contact with the electrodes [3]. In this work, a polymer based matrix containing poly(ethylene oxide) (PEO), lithium bis (trifluoromethylsulphonyl)imide (LiTFSI), tetra(ethylene glycol dimethyl ether) (G4) and a photoinitiator was added with LLZO particles, thoroughly mixed, formed into a film and cross-linked under UV radiation to obtain a composite hybrid electrolyte [4]. This easy procedure allows obtaining self-standing CPEs with desirable properties of flexibility, shape retention upon thermal stress, improved interfacial contact with the electrodes and ionic conductivity suitable for practical application. Lab-scale all solid lithium metal cells assembled with the CPEs and lithium iron phosphate (LFP) cathodes demonstrated specific capacities up to 125 mAh g-1 at 1C rate and could work for hundreds of cycles at ambient temperature. [1] B. Liu, Y. Gong, K. Fu, X. Han, Y. Yao, G. Pastel, C. Yang, H. Xie, E.D. Wachsman, and L. Hu, ACS Appl. Mater. Interfaces 9 (2017) 18809-18815. [2] H. Duan, H. Zheng, Y. Zhou, B. Xu, and H. Liu, Solid State Ionics (2017) in press. [3] C. K. Chan, T. Yang, and J.M. Weller, Electrochim. Acta 253 (2017) 268?280. [4] L. Porcarelli, C. Gerbaldi, F. Bella, and Jijeesh R. Nair, Sci. Rep. 6 (2016) 19892.

Authors : Fabrizio Murgia, Matteo Brighi, Radovan ?erný
Affiliations : Laboratory of Crystallography, Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, Ch-1211, Geneva, Switzerland

Resume : The demand of portable energy has grown during last 25 years, due to the spread of electronic personal devices and it will increase to boost the turn toward an oil-free mobility.[1] Such revolution based on Li-ion cell, has to face many constraints, i.e. the costs of raw materials and the security issues due to the use of a flammable electrolyte.[2] Na-based solid-state batteries could tackle these hurdles. They use the more abundant sodium as charge carrier and they feature a safer, solid material as electrolyte. Herein, the novel Na4(CB11H12)2(B12H12) was synthetized by solid-state ball-milling. It shows high Na+ conductivity, 1 mS cm-1 at 20°C, which increases to 10 mS cm-1 at 100 °C (Ea=136 meV). CV performed with a specific setup for solid electrolytes[3] revealed an excellent electrochemical stability, up to 4.1 V vs. Na+/Na. Preliminary tests on the electrolyte?s stability toward metallic Na in symmetric cells showed a limited electrolyte-electrode compatibility, (increase of the internal cell resistance) as already observed elsewhere.[4] Replacing Na by Na-Sn alloy a stable Na+ shuttling has been achieved, with low polarization over one month of cycling. In situ monitoring of the internal cell resistance by EIS confirmed the good stability of the electrolyte-electrode interface. [1] Zeier et al Nat Ener 1 (2016) 16141 [2] Sun et al Nano Ener 33 (2017) 363 [3] Tian et al Energy Environ Sci 10 (2017) 1150 [4] Iermakova et al J Electrochem Soc 162 (2015) A7060

Authors : P. Kehne (1), C. Guhl (2), Q. Ma (3), Frank Tietz (3), R. Hausbrandt (2), P. Komissinskiy (1)
Affiliations : (1) Advanced thin film technology; TU-Darmstadt Germany, (2) Surface science; TU-Darmstadt Germany, (3) Forschungszentrum Jülich Gemany,

Resume : Sodium-ion batteries for large-scale energy storage have recently attracted attention due to larger reserves of raw materials and possibly lower cost in comparison with lithium-ion cells. Batteries following an all-solid-state approach promise higher charging rates, less flammability and the minimization of hazardous material but challenge scientists with high interface resistivities. Here we report on the connection between the interface resistivity and battery performance in sodium all-solid-state batteries with Na-super ionic conductor Na3.3Sc0.3Zr1.7Si2PO12 (NASICON) and ß??-alumina solid state electrolytes. Experimental batteries were produced with Pulsed Laser deposited (PLD) NaxCoO2 films on solid electrolyte substrates. NaxCoO2/Nasicon/Na and NaxCoO2/ß??-alumina/Na Swagelok-type cells were cycled at room temperature with intermediate electrochemical impedance measurements. Interface resistances between the cathode, the solid electrolyte and the sodium anode were identified and monitored with increasing cycling number. Optimized all-solid-state batteries were cycled at rates between C/5 and 2C in a voltage range of 2.0 and 4.2 V. They exhibit interface resistivity?s of 600 Ohm cm² and specific capacities of 125 mAh/g with a capacity fading of only 10% over 1000 cycles.

Solid State Electronic Devices (II): Resistive Switching : John Paul Strachan and Anna Palau
Authors : Susanne Hoffmann-Eifert
Affiliations : Peter Gruenberg Institute, Forschungszentrum Juelich GmbH, 52425 Juelich, Germany

Resume : Redox-based resistive switching random access memory (ReRAM) is considered as promising future low energy non-volatile storage device with high-speed data access and high reliability. Valence-change-memory (VCM) cells typically require an electroforming step to create conductive paths in the mixed ionic-electronic conducting (MIEC) oxide by means of local extraction of oxygen. For the resulting filamentary-type bipolar resistive switching behavior oxygen vacancy drift/diffusion processes play a major role. However, with decreasing device dimensions the effect of oxygen exchange reactions between the MIEC switching layer and the electrodes becomes more pronounced. Recently, the importance of oxygen exchange reactions at the interface of Ta2O5 and the chemically reactive electrode has been demonstrated. Additionally, a coexistence of switching events of opposite polarity has recently been reported for cells built of heteroepitaxial SrTiO3 films as well as for crossbar structures made of nano-crystalline TiO2 layers. Ultra-high density integration of massively connected ReRAM cells into three-dimensional blocks for future beyond-von Neumann memory architectures requires a deeper knowledge on the switching behavior of nano-scaled devices. This includes a deeper understanding of the competition between oxygen ion drift/diffusion vs. oxygen exchange reactions. The presentation will address these questions with a focus on Pt/3-5 nm TiO2/Ti/Pt nano-crossbar devices which show a coexistence of two switching polarities, in detail, the counter-eightwise (c8w) and the eightwise (8w) behavior. For the studied cells, the two switching modes share one state, this is that the c8w-HRS equals the 8w-LRS*.

Authors : Thomas Heisig1, Christoph Baeumer1, Ute Gries2, Michael P. Mueller2, Camilla La Torre3, Michael Luebben3, Nicolas Raab1, Hongchu Du4, Stephan Menzel3, David N. Mueller1, Ilia Valov1,3, Chun-Lin Jia4, Joachim Mayer4, Rainer Waser1,3, Roger A. De Souza2, Regina Dittmann1
Affiliations : 1 Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany 2 Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany 3 Institute of Electronic Materials, IWE2, RWTH Aachen University, 52056 Aachen, Germany 4 Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Juelich GmbH and RWTH Aachen University, 52425 Juelich, Germany

Resume : Resistive switching based on transition metal oxide memristive devices is suspected to be caused by the electric field driven motion and internal redistribution of oxygen vacancies. Deriving the detailed mechanistic picture of the switching process is complicated, however, by the frequently observed influence of the surrounding atmosphere. Although an increasing number of models used to explain atmospheric influences are based on the release and reincorporation of oxygen species, the experimental evidence for these exchange processes is scarce. To investigate the role of oxygen during resistive switching in greater detail, we use isotope labeling experiments in N2/H218O tracer gas atmosphere combined with time-of-flight secondary ion mass spectrometry. We explicitly demonstrate that oxygen incorporation processes take place in resistive switching SrTiO3-based memristive devices. Specifically, we observe that during the RESET operation, voltage driven oxygen incorporation occurs predominantly by water present in the atmosphere. These findings clarify in detail the exchange of oxygen between SrTiO3 and the ambient atmosphere during device operation and resolve the role of humidity for the oxidation process during the RESET operation.

Authors : D. Pla(a), R. Rodriguez-Lamas(a), B. Meunier(a), O. Chaix-Pluchery(a), M. Boudard(a), L. Rapenne(a), H. Roussel(a), Q. Rafhay (b) C. Jimenez(a) and M. Burriel(a)
Affiliations : (a) Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France (b) Univ. Grenoble Alpes, CNRS, Grenoble INP, IMEP-LAHC, F-38000 Grenoble, France

Resume : This work presents the design of memristive heterostructures using LaMnO3+? (LMO) as ?sandwiched? switching material between the top and bottom electrodes. A number of different strategies were explored to integrate these manganite films on silicon-based devices, overcoming the challenge of the high temperatures required for their deposition. LMO thin films were prepared by pulsed injection MOCVD and were fully characterized using a combination of microscopic, spectroscopic and physical techniques. A rhombohedral phase is obtained for films treated under O2, pointing out to higher oxygen concentration (3+?); whereas films treated under Ar showed an orthorhombic phase, linked to a lower oxygen content (higher VO.. concentration). The resistivity values obtained have been related to the structural, compositional and electronic properties of the LMO films. The resistive switching (RS) response for different LMO-based devices was optimized as a function of the nature of the electrodes, the LMO microstructure, the forming step and the set/reset voltages applied. Bipolar RS with different memory windows was attained by tuning the voltage and the current compliance. The nature of the switching mechanism will also be discussed (filamentary vs interfacial). The RS results obtained are very promising, showing a large resistance window for operation (up to 3 orders of magnitude) and using low set/reset voltages for the three different top metal electrode configurations tested.

Authors : Hongwei Tan, Qihang Qin, Sayani Majumdar, Sebastiaan van Dijken
Affiliations : Nanospin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland. Email of the presenting author:

Resume : The human brain processes large amounts of information in parallel at low energy cost. The energy-efficiency, cognitive ability, and versatility of this integrated memory and logic system have inspired the field of neuromorphic computing. Synapses are one of the most vital components of neuromorphic networks. They act as connections between neurons. Voltage pulses that are applied to a synapse modify the synaptic weight through long-term potentiation (LTP) and short-term plasticity (STP), enabling memory and cognitive activities. Memristors with gradually modifying conductivity levels can mimic the behavior of biological synapses. Low energy consumption, fast operation and small dimensions are essential requirements for the integration of memristors into neural networks. In recent years, several types of memristive devices have emerged, including devices that are based on ferroelectric polarization switching, phase changes, magnetization dynamics, and ion migration. In our previous work, we have shown that oxide tunnel junctions with ionic interfaces are able to show large resistive switching between on and off states due to electric-field controlled migration of oxygen vacancies. In this work, we demonstrate that the resistance of junctions with a La2/3Sr1/3MnO3 bottom electrode, a Au top electrode, and a thin SrTiO3 tunnel barrier can be continuously set to any intermediate states by controlled migration of oxygen vacancies under varying voltage pulses. This memristive behavior together with synaptic features like long-term potentiation and depression makes them attractive for applications as electronic synapse in neural networks.

Authors : Hehe Zhang1, Sijung Yoo3, Cheol Seong Hwang3, Carsten Funck2, Stephan Menzel1, and Susanne Hoffmann-Eifert1
Affiliations : 1 Peter Grünberg Institute, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany 2 Institute of Electronic Materials, RWTH Aachen University, 52062 Aachen, Germany 3 Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Korea

Resume : Resistive switching memory (ReRAM) is a prominent candidate for next generation non-volatile storage devices. Redox-type valence change memories (VCM) based on HfO2 and Ta2O5 switching layers typically show a counter-eightwise (c8w) polarity of the switching loop which is clearly associated with filamentary-type switching. Interestingly for epitaxial grown SrTiO3 based devices also switching loops of eightwise (8w) polarity have been reported. Recently, 8w switching hysteresis has also been reported for cells based on polycrystalline TiO2 thin films. Here, we report on TiO2 based nano-crossbar cells of Pt/(Al2O3)/TiO2/Ti/Pt with a Al2O3 layer of 0 to 3 nm and a TiO2 layer of 3 to 6 nm. To achieve conformal growth on the 100 nm wide Pt bottom electrode lines the oxide layers were deposited by thermal atomic layer deposition. The 10 nm Ti oxygen exchange layer and the Pt layer were grown by e-beam evaporation. Cells from pure TiO2 as well as bilayer cells with up to 2 nm of Al2O3 reveal a coexistence of the two switching polarities (c8w and 8w) in the same device. The 8w bipolar resistance switching mode can be operated in the current range below 100 µA and offers the possibility of programming stable multilevel high resistance states. In order to understand the switching behavior in these devices, different high resistance states of the 8w switching mode were carefully analyzed with respect to their current dependence on temperature and electric field. The corresponding I(V, T) behaviors were successfully characterized by application of the Simmons? formula for tunneling through an asymmetric barrier. With the simulation parameters, a qualitative understanding of the multilevel switching behavior in both mono- and bilayer cells is established.

Authors : Andrey A. Chernov(1,2,3), Damir R. Islamov(1,2), Andrey A. Pil?nik(1,2,3)
Affiliations : (1)Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090, Russia; (2)Novosibirsk State University, Novosibirsk 630090, Russia; (3)Kutateladze Institute of Thermophysics SB RAS, Novosibirsk 630090, Russia

Resume : Implementation of a memristor suitable for computing and data storing is a one of rising recent research trends. Many applications are to be implemented within a one- and a multi-bit memristors. It can be used to increase the information capacity of RAM elements as well as to be used for neuromorphic computational systems that can bring the AI to a completely new level. Although it is simple enough to implement the memristor using macrostructures, it is not applicable for the computing purposes. Research on thin metals oxide films shows the applicability of such an object for the objective ? creating the memristor with desirable characteristics. It is tended to connect the memristive switch with the filament formation that occurs when a current pulse passes over a dielectric. The aim of the work is obtaining a model of dynamic memristor switching possessing by analysis of charge transport in high-k affected by the presence of defects and heat release. A continuum filament growth model is formulated. The model is the boundary value problem, which includes a nonstationary heat conduction equation with a nonlinear Joule heat source, Poisson equation, and Shockley-Read-Hall equations considering strong electron-phonon interactions in trap ionization and charge transport processes. The results of computer simulations of the model are current-voltage characteristics of a memristor element. The work was supported by the Russian Science Foundation, grant #16-19-00002.

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Interface & Surface Phenomena (II) : Felix Gunkel and Rotraut Merkle
Authors : William C. Chueh
Affiliations : Department of Materials Science & Engineering, Stanford University

Resume : Mixed ionic and electronic conductors can change their chemical composition through mass exchange with the external environment, both chemically and electrochemically. Examples include oxygen-insertion compounds such as ceria oxide, and lithium-insertion compounds such as lithium cobalt oxide. The insertion or removal of mass such as oxygen or lithium causes an expansion or a contraction of the lattice, resulting in a chemo-mechanical coupling. In this talk I will present three special cases of such coupling. The first case is biaxially-strained, dense thin film of cerium oxide. The tetragonal distortion of the nominally cubic crystal gives rise to splitting of the oxygen redox levels, leading to a non-monotonic dependence of oxygen concentration on strain. The second case is porous agglomerate of lithium transition metal layered oxide, which exhibits significant compositional heterogeneity at equilibrium, again due to chemo-mechanical coupling. Finally, I will discuss the importance of chemo-mechanics at interfaces such as grain boundaries.

Authors : Markus Kubicek, Edvinas Navickas, Andreas Nenning, Stefanie Taibl, Herbert Hutter, Jürgen Fleig
Affiliations : Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, Vienna, A-1060, Austria

Resume : The oxygen exchange reaction on mixed ionic electronic conducting (MIEC) oxides is highly important for solid oxide fuel cells, sensors or oxygen permeation membranes. To characterize the kinetics of surface oxygen exchange, isotope exchange depth profiling (IEDP) and electrochemical impedance spectroscopy (EIS) are usually regarded as complementary tools, simply assuming the electrical (kq) and tracer (k*) surface exchange coefficients to be identical. Only very few studies directly compared kq and k* of solid?gas interfaces under identical conditions. In this work it is shown that kq and k* may strongly differ for one material and different humidification, but also between different MIEC materials. In-situ EIS with oxygen exchange experiments were performed on La0.8Sr0.2MnO3-?, La0.6Sr0.4CoO3-?, La0.5Sr0.5Co0.2Fe0.8O3-?, La0.6Sr0.4FeO3-? and SrTi0.3Fe0.7O3-? thin films. Experiments were performed in usual isotope exchange conditions (18O2), in dehumidified 18O2 isotope (by a molecular sieve), humid oxidizing (18O tracered O2 and H2O) and humid reducing (H2 tracer H2O) atmospheres. In dried isotope gas kq and k* were rather similar (k*/kq=1.5), whereas in humid atmospheres the difference between k* and kq becomes tremendous (k*/kq=1000) for some materials. The reason behind this is a fast water adsorption and dissociation on surface oxygen vacancies, by forming surface hydroxyl groups. Experimentally determined k* and kq values are discussed in terms of electrochemically relevant oxygen exchange and temperature dependence for five different MIECs.

Authors : Vincent Thoréton(a), Mathew Niania(b), John Druce(a), Tatsumi Ishihara(a), John Kilner(a,b)
Affiliations : (a) WPI-International Institute for Carbon-Neutral Energy Research (I2CNER), Fukuoka, Japan. (b) Department of Materials, Imperial College London, London, UK.

Resume : The reversible operation of Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC) for the interconversion of electrical and chemical energy requires a good electro-catalytic activity and the long-term stability of the ceramic air electrode with the surrounding atmosphere. In particular, the interaction of oxygen-bearing molecules in the feed gas with the electrode surface is a critical process to understand. This work investigates the influence of water vapour (up to 100 mbar) and carbon dioxide (up to 5 mbar) on the evolution of the surface chemistry and on the changes to the oxygen transport kinetics of LSCF6428 as a model air-electrode. A ?back exchange? protocol [1,2] and H218O labelling are used to probe the oxygen transport kinetics under 0.20 bar of oxygen. A systematic increase of the surface exchange kinetics is observed in the presence of steam or CO2. Unexpectedly, the diffusion kinetics are also affected. The evolution of the surface with time and the exposure to different atmospheres is followed, in particular by the mean of Low Energy Ion Scattering (LEIS). [1] S.J. Cooper, M. Niania, F. Hoffmann, J.A. Kilner, Phys. Chem. Chem. Phys. (2017). [2] H. Téllez, J. Druce, S.J. Cooper, J.A. Kilner, Sci. & Tech. of Adv. Mat. (2017). This work was supported by JSPS KAKENHI Grant Number 16K18236. This work was supported by the WPI program. This work was supported by JSPS Core-to-Core Program, A. Advanced Research Networks.

Authors : Alexander Hutterer, Jürgen Fleig, Alexander K. Opitz
Affiliations : TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria

Resume : Pt/YSZ is one of the best studied model systems for oxygen reduction in solid state electrochemistry with a long history of research and especially at high temperatures it is the prototype of a triple phase boundary (TPB) active electrode. However, the exact reaction mechanism of oxygen reduction on Pt/YSZ in general and its rate limiting elementary step in particular are still not completely understood. To shed further light on the oxygen exchange kinetics of this system the polarization resistance of micro-patterned Pt thin film electrodes on YSZ (111) single crystals was studied by means of impedance spectroscopy at low oxygen partial pressures between 0.1 and 0.01 mbar. Under these conditions a hysteretic behavior of the polarization resistance could be found for temperature sweeps between 500 and 850 °C. The associated step-like increase/decrease of the polarization resistance was further analyzed by variation of the electrode geometry to identify potential changes in the electrochemically active region. Moreover, possible reaction mechanisms explaining this yet unknown behavior of Pt(O2)/YSZ are discussed.

Authors : E. A. Kotomin, Yu. A. Mastrikov, R. Merkle, M. M. Kuklja, J. Maier
Affiliations : Max Planck Institute for Solid State Research, Stuttgart, Germany; Institute for Solid State Physics, University of Latvia, Riga; Mater Sci and Eng Dept, University of Maryland, USA

Resume : La1-xSrxMnO3 (LSM) was one of the first perovskites employed as SOFC cathode and is still used in composites. We analyzed oxygen adsorption, dissociation and migration on the (001) MnO2-terminated surface [1]. In pure LaMnO3, the MnO2 (001) termination was found to be the energetically most stable, however with an increase of Sr doping, the (La,Sr)O termination becomes more favorable [2]. In this talk, we compare results of first principles calculations on the elementary steps (oxygen vacancy formation, O2 molecule and O atom adsorption) of oxygen reduction on the polar (La,Sr)O and MnO2 (001) terminations. Slab calculations were performed using VASP with GGA functionals. In contrast to the MnO2 termination, the vacancy formation energy on (La,Sr)O is larger, strongly reducing the surface vacancy concentration. Our approach distinguishes two effects - different surface terminations and slab cation stoichiometry (ratio of (La,Sr) ions to Mn affecting the average Mn oxidation state). The equilibrium oxygen adsorbate concentration was found to be two orders of magnitude larger for (La,Sr)O, but on the other hand, the surface oxygen vacancy concentration is smaller by nearly six orders of magnitude. Therefore, the oxygen reduction rate on (La,Sr)O is expected to be significantly lower than on MnO2. [1] Y.A. Mastrikov, R. Merkle, E. Heifets, E. A. Kotomin, J. Maier, J.Phys.Chem.C 114, 3017 (2010). [2] S. Piskunov, E. Heifets, T. Jacob, E.A. Kotomin, E. Spohr, Phys. Rev.B 78, 121406 (2008)

Interface & Surface Phenomena (III) : Markus Kubicek and Mónica Burriel
Authors : José Santiso1,*, Núria Bagués1,2, Bryan D. Esser3, Robert E.A. Williams3, Dave W. McComb3, Zorica Konstantinovic4, Lluís Balcells2, and Felip Sandiumenge2
Affiliations : 1 Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST Campus UAB, Bellaterra, 08193 Barcelona, Catalonia, Spain. 2 Institut de Ciència de Materials de Barcelona, ICMAB-CSIC Campus de la UAB, 08193 Bellaterra, Catalonia, Spain. 3 Center for Electron Microscopy and Analysis The Ohio State University, Columbus, USA. 4 Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia.

Resume : In heteroepitaxial thin film growth the mismatch between film and substrate cell structures causes the films to start growing with a certain strain until a certain critical thickness is achieved. Above this thickness the strain energy starts to be gradually released by different possible mechanisms. One of the most common mechanisms for strain relaxation is the formation of misfit dislocations (MDs). In perovskite oxides the most common dislocations are of pure edge character following characteristic crystallographic directions, depending on the film orientation and substrate cut. The dislocations start forming at the film surface and diffuse across the film thickness until they reach the film-substrate interface. The dislocation core is intrinsically a discontinuity in the material structure and therefore it can show different material properties at a local scale. Concomitantly, the film regions surrounding one single MD core are submitted to a particularly strong strain field, compressive or tensile at opposite regions of the MD core. This strain field may as well substantially modify the equilibrium structure giving rise to differences in the material functionality around these local dislocated regions. Under particular conditions the dislocation strain fields of adjacent MDs interact generating a self-arrangement and forming organised arrays with a few nanometres scale spacing. These region can be, therefore, considered as a nanostructure embedded at the interfacial region between a relaxed film and the substrate, and pave the way to interesting application in nanodevices, as well of facilitating the fundamental study of the peculiar functionalities of these 1D objects. In this study we present different cases of MDs arrangement during epitaxial growth, particularly in compressively strained LaSrMnO3 grown on LaAlO3(100) substrates. The dislocation distribution is readily analysed by X-ray diffraction and AFM [1,2]. The structure of the core and surrounding area of the MDs is analysed by HRTEM, as well as its chemical and electronic configuration at atomic-column resolution by means of combined EDS and EELS analysis.[3] These studies reveal a complex interplay between local anionic and cationic composition as well as changes in the transition metal oxidation state which depend on the compressive or tensile region around the MD core. The mechanisms underlying the changes in the local structure and composition in the dislocated regions result from a combination of elastic and electrostatic energy degrees of freedom and the sign and magnitude of the film-substrate mismatch. [1] J. Santiso et al., ACS Appl Mater Interfaces. 8 (2016)16823-16832 [2] F. Sandiumenge, Adv. Mater. Interfaces 3 (2016) 1600106. [3] N. Bagués et al., Adv. Funct. Mater. (2017) 1704437. doi: 10.1002/adfm.201704437

Authors : George F. Harrington(a,b,c,e), Nicola H. Perry(c,e,f), Kazunari Sasaki(a,b), Bilge Yildiz(c,b), and Harry L. Tuller(c,b,e)
Affiliations : (a) Center for Co-Evolutional Social Systems, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan (b) Next-Generation Fuel Cell Research Centre, Kyushu University, 744 Motooka, Nishi-ku Fukuoka 819-0395, Japan (c) Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139, U.S.A. (d) Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139, U.S.A. (e) WPI-International Institute for Carbon-Neutral Energy Research, Kyushu University, 744 Motooka, Nishi-ku Fukuoka 819-0395, Japan (f) Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL 61801, U.S.A

Resume : Pr substituted CeO2 (PCO) is an excellent model mixed ionic-electronic conductor (MIEC) for fundamental studies and has potential applications in intermediate temperature electrochemical devices. In high pO2 conditions, vacancy formation is accompanied by the reduction of Pr4 to Pr3 and the material displays MIEC behaviour via oxygen vacancy migration and small polaron hopping between the valence-active cations. PCO has been extensively studied, and the defect chemistry, chemical expansion, and transport properties are well described in the bulk material. This makes it an excellent choice for studying the interplay of strain, space-charge, and electro-chemo-mechanical coupling effects at heterogeneous interfaces, including their impact on transport properties. We have fabricated multilayer films of alternating Pr0.1Ce0.9O2-d and SrTiO3 (STO) layers using pulsed laser deposition. The nanostructures have been characterised in detail using X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy combined with electron energy loss spectroscopy. The conductivity of the layers shows a dramatic weakening of the pO2 dependence as the density of the interfaces is increased, which is consistent with a lowering of the enthalpy for Pr reduction. This study represents an excellent example of the significant potential to tailor the ionic and electronic transport at oxide interfaces

Authors : A. F. Zurhelle[1,3], R. Waser[1,2,3], S. Menzel[2,3], F. Gunkel[1,3]
Affiliations : 1 Institute of Electronic Materials (IWE 2), RWTH Aachen University, 52074 Aachen, Germany 2 Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany 3 JARA ? Fundamentals of Future Information Technology

Resume : Oxide heterointerfaces can harbor electronic systems with a variety of remarkable properties, like superconductivity, magnetoresistance or tunable metal?insulator transitions. Since the discovery that a two-dimensional electron gas (2DEG) can be formed at the LaAlO3?SrTiO3 interface, SrTiO3-based interfaces have been in focus of research. For many SrTiO3-based interfaces, such as amorphous LaAlO3?SrTiO3, gamma-Al2O3?SrTiO3, or irradiated SrTiO3, the electron density is determined by oxygen vacancies, which accumulate at the interface and act as donor dopants. In recent experiments, it has been shown that the spatial distribution of oxygen vacancies can be controlled by annealing and thereby the electron density can be tuned. To support further experimental efforts, we describe the redistribution of oxygen vacancies and the corresponding changes in electron density during annealing with a time-dependent drift?diffusion model. This model is based on space-charge theory: the lowered chemical potential of oxygen vacancies at surfaces and interfaces is considered as thermodynamical driving force for the oxygen vacancy redistribution. We show that oxygen vacancies form a depletion layer close to the interface, which implies a spatial separation of oxygen vacancies (donors) and electrons. The timescale of this redistribution strongly depends on the ambient conditions, e. g. it ranges from weeks at 300 K to seconds at 473 K.

Authors : Hongguang Wang, Vesna Srot, Yi Wang, Hans Boschker, Jochen Mannhart and Peter A. van Aken
Affiliations : Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany

Resume : With the progress of epitaxial growth technology, complex oxide hetero-epitaxy attracts intense research interest due to the distinctive electrical, magnetic and optical properties which are not present in their bulk constituent. Lattice mismatch engineering can tailor the interplay between microstructure and properties of epitaxial-grown layers. In case of large lattice mismatch, defects like oxygen vacancies and misfit dislocations will appear for accommodating epitaxial strain. Therefore the development of an overall understanding about their occurrence and relevance toward electronic structure is of great significance. Here, by using a combination of aberration-corrected transmission electron microscopy imaging and electron energy-loss spectroscopy, we performed atomic-scale investigations of the microstructure and electronic structure of defects in a SrMnO3 (SMO) epitaxial thin film on SrTiO3 (STO) grown by pulsed-laser deposition. A wide distribution of defects with different morphologies varying from misfit dislocations to dislocation-associated trenches was observed. Simultaneously acquired atomically resolved high-angle annular dark-field and annular bright-field images were used to evaluate the microstructure of these defects and to analyze the strain state of the SMO thin film, demonstrating a concomitant strain release. The energy-loss near-edge structures of the O-K and Mn-L2,3 edges reveal a noticeable electronic structure variation in the vicinity of the defect core. The origin of the electronic structure evolution will be discussed.

Authors : Nan Yang?1??C. Aruta?2?
Affiliations : ?1?School of Physical Science and Technology, ShanghaiTech University, 201210 Shanghai, China? ?2?National Research Council CNR-SPIN, and Department DICII, University of Roma ?Tor Vergata?, 00133 Rome, Italy

Resume : The role of trivalent rare-earth dopants on the cerium oxidation state has been systematically studied by in situ photoemission spectroscopy with synchrotron radiation for 10 mol % rareearth doped epitaxial ceria films. It was found that dopant rare-earths with smaller ionic radius foster the formation of Ce3+ by releasing the stress strength induced by the cation substitution. With a decrease of the dopant ionic radius from La3+ to Yb3+ , the out-of-plane axis parameter of the crystal lattice decreases without introducing macroscopic defects. The high crystal quality of our films allowed us to comparatively study both the ionic conductivity and surface reactivity ruling out the influence of structural defects. The measured increase in the activation energy of films and their enhanced surface reactivity can be explained in terms of the dopant ionic radius effects on the Ce4+ ? Ce3+ reduction as a result of lattice relaxation. Such findings open new perspectives in designing ceria-based materials with tailored properties by choosing suitable cation substitution.[1] [1] Nan Yang, Pasquale Orgiani, Elisabetta Di Bartolomeo, Vittorio Foglietti, Piero Torelli, Anton V. Ievlev, Giorgio Rossi, Silvia Licoccia, Giuseppe Balestrino, Sergei V. Kalinin, and Carmela Aruta, J. Phys. Chem. C, 2017, 121, 8841?8849.

Authors : Aoife K. Lucid, Graeme W. Watson
Affiliations : School of Chemistry and CRANN, Trinity College Dublin

Resume : Current solid oxide cells (SOCs) require temperatures in the region of 1000°C to operate. This is primarily due to the fact that current generation SOC electrolytes, such as YSZ, require high temperatures for sufficient ionic diffusion of the oxide ions to occur. It has been suggested that replacing YSZ with samarium doped ceria (SDC) or gadolinium doped ceria (GDC) would reduce the operating temperature of SOFCs into the intermediate temperature range of 600-800°C, thus greatly reducing operating costs and increasing efficiency. It has been suggested that the strain which is induced in epitaxial thin films of these materials can result in enhancements in conductivity, though the degree of enhancement is often debated. There has been little theoretical investigation into oxide ion conductivity of SDC and GDC at surfaces and strained surfaces. Classical molecular dynamics simulations can be used to study the strain effects in these systems. We utilise a polarisable force field, known as the dipole polarisable ion model (DIPPIM), which has been derived from ab-initio data for ceria with a range of trivalent dopants. Biaxial tensile strains are applied to the (111), (221) and (210) slabs as this is a realistic representation of epitaxial thin film growth. We will discuss the effect of the surfaces and strained surfaces on the performance of SDC and GDC as oxide ion conductors. We have found that the ionic diffusion at the surface is highly surface dependent.

Authors : S. G. Ebbinghaus, M. Breitenbach, T. Buttlar, and T. Walther
Affiliations : Martin Luther University Halle-Wittenberg Institute of Chemistry Kurt-Mothes-Str. 2 06120 Halle(Saale)

Resume : In multiferroics, the coupling between the different ferroic ordering phenomena opens the door for a large variety of applications, e.g. as sensors or in data storage devices. In this contribution we report on multiferroic composites consisting of BaTiO3 as ferroelectric component in combination with either ferrimagnetic ferrite spinels MFe2O4 (e.g. M = Co, Ni) or ferromagnetic metals/alloys (Ni, Co1/3Fe2/3). As an interface-mediated effect the magnetoelectric coupling strongly depends on the connectivity of the components. We have prepared 0?3 composites, i.e. particles of the ferro-/ferrimagnetic phase embedded in the BaTiO3 matrix, by a polyol-assisted synthesis followed by reductive sintering and mild reoxidation. On the other hand, the eutectic crystallization of CoFe2O4/BaTiO3 melts in an optical floating zone furnace leads to composites with 3?3-connectivity. A variety of different geometric structures with very smooth interfaces are formed by self-organization. All samples have been investigated with a broad spectrum of characterization techniques comprising XRD, SEM/EDX, impedance spectroscopy and temperature- and field-dependent magnetic measurements. The magnetoelectric coefficients have been studied in detail with respect to different compositions, temperature, external magnetic field and frequency.

Poster Session 2 : David S. Mebane
Authors : Hyung Jong Choi, Dong Hwan Kim, Manjin Kim, Neoh Ke Chean, You Kai Li, Dong Young Jang, Joon Hyung Shim
Affiliations : School of Mechanical Engineering, Korea University 145 Anam-ro Seongbuk-gu, Seoul 02841, Korea

Resume : There has been a lot of efforts to develop catalyst with better performance than platinum (Pt) in the low and medium temperature ranges as Pt is precious and expensive. Pt or Pt-alloys have been regarded as top performance catalysts for oxygen reduction reactions (ORRs) essential for a variety of electrochemical devices, including batteries, fuel cells, electrolyzers and gas filters. ORRs occur through sequential reactions in case of using oxygen ion conducting electrolytes and non-ion conducting metal catalysts: i) adsorption of oxygen gas on the catalyst surface, ii) formation of oxygen monomers to remove O-O bonds, iii) surface-transport of the O-monomers to charge transfer sites, iv) reduction and ionization of the O-monomers, and v) incorporation of oxygen ions into the electrolytes [1]. Among these steps, reduction of O-monomer is considered as the most energetically unfavorable reaction that determine the overall process rate. In this respect, maximizing triple phase boundaries (TPBs) where catalyst, electrolyte and space are in physical contact and the charge transfer of the O-monomer can occur is expected to significantly improve the ORR. Our approach is to decorate the surface of the metal catalyst with percolated ion-conducting oxide nano-particles to extend TPBs to the surface catalyst. As a metal-backbone catalyst that can replace platinum, silver (Ag) can be thought of because the ORR on the Ag surface has been reported to be as active as Pt in the intermediate temperature range [2,3]. Our group has tried doped zirconia (ZrO2) and ceria (CeOx) [4-6] as ion conductive nanoparticles. The performance of the Ag oxide composite catalyst was evaluated as the anode of a solid oxide fuel cell at temperatures of 300-500°C. As a result, we found that Ag with optimized scandia-doped ZrO2 (ScSZ) nanoparticles is superior to Pt in terms of fuel cell output, ORR impedance and long-term stability [6]. Ag catalysts containing yttria-doped ZrO2 (YSZ) nanoparticles showed comparable performance to Pt catalysts [4], while the performance of doped ceria was found to be far less than that [5]. In this presentation, we will discuss detailed performance of Ag-oxide nano-particle composite ORR catalysts and their underlying mechanisms. References (1) H. Uchida, M. Yoshida, and M. Watanabe, J. Electrochem. Soc. 1999, 146(1), 1. (2) T.-J. Huang, X.-D. Shen, C.-L. Chou, J. Power Sources 2009, 187, 348. (3) M. Gödickemeier, K. Sasaki, L. Gauckler, I. Riess, J. Electrochem. Soc. 1997, 144, 1635 (4) Y. K. Li, H. J. Choi, H. K. Kim, N. K. Chean, M. Kim, J. Koo, H. J. Jeong, D. Y. Jang, and J. H. Shim, J. Power Sources 2015, 295, 175. (5) K. C. Neoh, G. D. Han, M. Kim, J. W. Kim, H. J. Choi, S. W. Park and J. H.Shim, Nanotechnology 2016, 27, 185403. (6) H. J. Choi, M. Kim, K. C. Neoh, D. Y. Jang, H. J. Kim, J. M. Shin, G. Kim, and J. H. Shim, Adv. Energy Mater. 2016, 1601956.

Authors : Iu-Fan Chen, Chun-Fu Lu and Wei-Fang Su
Affiliations : Department of Materials Science and Engineering, National Taiwan University, Taipei City, Taiwan 10617

Resume : Metal-Organic Frameworks (MOFs) are studied extensively in applications like catalysts, gas storage and sensors due to their various functional groups and porous structures. Two dimensional MOFs such as triphenylene-based materials show excellent charge transport property but thin film fabrication and organic ligand synthesis are difficult. In this work, we synthesize thiol-based organic ligand, benzenehexathiol (BHT), by a simple one-pot reaction. This facile method is safer and faster than conventional synthesis procedure which requires using liquid ammonia as solvent. We also demonstrate an efficient approach for fabrication of MOFs thin film by growing MOFs on functionalized substrates. Group 11 elements (Cu, Ag and Au) are used in this study to achieve planar coordination of metal ions and thiols in BHT. Functional group of silane on the substrate has affinity to BHT or metal ions, leading to high quality MOFs thin films. This general method can be used to control the growth of 2D MOFs on silicon substrate. Cu-BHT exhibits better redox performance in water than AgBHT and AuBHT. We fabricate a glucose sensor using 2D film of Cu-BHT that can sense 30mM glucose in water.

Authors : D. Gryaznov(1,2), M. Hödl(2), R. Merkle(2), E. A. Kotomin(1,2), J. Maier(2)
Affiliations : (1) Institute for Solid State Physics, University of Latvia, Riga, Latvia (2) Max Planck Institute for Solid State Research, Stuttgart, Germany

Resume : Among ceramic fuel cells, protonic ceramic fuel cells (PCFC) attract growing interest. Proton-conducting ceramic electrolytes offer a higher ionic conductivity compared to oxide ion conductors, in particular at intermediate T (300-600°C). Finding optimum cathode materials with mixed protonic and electronic conductivity is crucial for PCFC performance. So far, proton concentrations were measured only for few cathode materials, e.g. Ba0.5Sr0.5Fe0.8Zn0.2O3-delta [1]. They are significantly smaller than for BaZr1-xYxO3-x/2 electrolyte materials under comparable conditions. Recent first principles calculations for La1-xSrxFeO3-delta [2] yielded protonic defects (hydroxide ions on regular oxygen sites) with similar geometry as in BaZr1-xYxO3-x/2 electrolytes but much less negative hydration enthalpy. In the present study, we extend the calculations to nonstoichiometric Ba1-xSrxFeO3-delta and compare results from CRYSTAL (atomic basis) and VASP (plane waves) codes. Correlations of protonic defect formation energies with parameters such as ion charges, local atomic coordination and bond lengths are analyzed to obtain an atomistic understanding of the adjusting screws determining proton uptake in PCFC cathode materials. A comparison of proton migration and proton uptake with other cathode materials will be drawn and discussed. [1] D. Poetzsch, R. Merkle, J. Maier, Faraday Discussions 182 (2015) 129 [2] D. Gryaznov, R. Merkle, E. Kotomin, J. Maier, J. Mater. Chem. A 4 (2016) 13093

Authors : Ehsan Mahboobi, Amin Yourdkhnai, Reza Poursalehi
Affiliations : Ehsan Mahboobi: Materials Engineering Department, Tarbiat Modares University, Tehran, IRAN; Amin Yourdkhnai: Materials Engineering Department, Tarbiat Modares University, Tehran, IRAN; Reza Poursalehi: Materials Engineering Department, Tarbiat Modares University, Tehran, IRAN

Resume : We present the synthesis and growth of iron phosphate polyanions films by a novel chemical method so called liquid phase deposition (LPD). LPD is a soft chemical method which was used initially for the thin film growth of metal oxides. This chemical technique is based on the slow hydrolysis of fluoro-metal complexes in the aqueous solutions by replacing the fluorine ions from the water soluble metal-fluoro complexes by OH- groups. Iron phosphate polyanion is known for its great applications as the cathode materials for the small ion batteries owing to their longer lifetime, better power density and high degree of safety compared to other cathode materials. Recently, our group has extended this method for the film growth of polyanionic compounds. Scanning electron microscopy (SEM) observations showed that the morphology, continuity and the phase composition of the films strongly depend on the deposition temperatures and the precursor concentrations. Those films grown at 60 and 75 °C with 4 dM of phosphor fluoro-complex concentration are highly uniform, free of cracks, pure and continuously cover the stainless substrates. Thickness of these films easily can be tailored in the range of 80 nm to 2.7 ?m simply by varying the deposition time. Finally, the electrochemical properties (cyclic voltammetry) of FePO4 films as cathodes for Li-ion battery applications on 316-stainless steel were investigated. Cyclic voltammetry analysis at 20 mV/s scan rate showed that pseudocapacitance of the films are thickness dependent and the maximum pseudocapacitance (72.8 F/g ) corresponds the films grown at 75 °C- 4 dM with 230nm thickness.

Authors : Julio García-Fayos(1), D. Gryaznov(2), David Catalan(1), E. A. Kotomin(2), Jose M. Serra(1)
Affiliations : (1) Instituto de Tecnología Química (Universidad Politécnica de Valencia ? Consejo Superior de Investigaciones Científicas), Valencia, Spain (2) Institute for Solid State Physics, University of Latvia, Riga, Latvia

Resume : Major sources for human-made CO2 emissions comprise the energy and the industrial sector including cement production. One of the most appropriate concepts to capture CO2 is the oxyfuel combustion. However, most of known highly permeable membrane materials show unwanted chemical instability against CO2 and other flue gas components. Therefore, new advanced membrane materials and components are needed for such technological processes as the oxyfuel combustion. In the present study, oxygen permeation tests were performed, in order to study the effect of CO2 on surface properties of the (La,Sr)FeO3 perovskite membranes. A theoretical model was developed and applied to an analysis of the experimental data. The obtained CO2 adsorption enthalpies are compared with the results of hybrid density functional (DFT) calculations. Subsequently, the hybrid DFT calculations allow for a deeper atomistic understanding of the CO2 adsorption. This includes the correlation between the adsorption enthalpy and stability of different atomic configurations for the CO2 adsorption and membrane basic properties, such as the Fe oxidation state, a role of surface vacancies, bond lengths and bond populations. A good agreement between the DFT adsorption enthalpies and measured ones suggested an important role of oxygen vacancies and confirmed the formation of carbonate phases.

Authors : Bartosz Kamecki, Piotr Winiarz, Sebastian Wachowski, Aleksandra Mielewczyk-Gry?, Piotr Jasi?ski, Maria Gazda
Affiliations : Gdansk University of Technology Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Narutowicza 11/12, 80-233 Gdansk, Poland; Gdansk University of Technology, Faculty of Electronics, Telecommunications and Informatics, Department of Biomedical Engineering Narutowicza 11/12, 80-233 Gda?sk, Poland

Resume : High temperature proton conductors (HTPCs) are promising materials for hydrogen energy conversion and storage. Among them acceptor doped lanthanum orthoniobate (LaNbO¬4¬) has total protonic conductivity reaching 10-3 S/cm at 900 °C. In our previous works we have shown antimony substitution on Nb site and its influence on structural properties and stability of the material. LaAsO4 also has been considered as proton conductor with total conductivity around 10-5 S/cm at 900°C. On this basis, it may be expected that LaSbO4 ? another member of the ABO4 group ? may also be considered as a potential candidate for proton conducting ceramics. Based on a few literature reports we have synthesized calcium doped LaSbO4 and LaAsO4 in order to study their proton conductivity. The materials have been thoroughly investigated, focusing on the influence of doping on electrical properties. Enhanced proton conductivity was expected due to A-site acceptor doping. Prepared samples were characterized by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), Dilatometry measurements and Electrochemical Impedance Spectroscopy (EIS). XRD results show that single phase LaSbO4 can be formed. SEM images confirmed dense microstructure of obtained samples. In particular, electrical conductivity has been studied as a function of temperature and oxygen partial pressure. This work was financially supported by the National Science Center, Poland Grant No. 2015/17/N/ST5/02813.

Authors : Antton Curutchet, Tangui Le Bahers
Affiliations : Univ Lyon, ENS de Lyon, CNRS, Université Lyon 1, Laboratoire de Chimie UMR 5182, Lyon, France

Resume : Geologists have known for almost one century the existence of natural photochromic minerals of the sodalite family. Although the community is mainly trying to develop new type of photochromic materials, almost no efforts were devoted to understand and develop these natural minerals known by the geologists for a long time. In this presentation, we will focus on natural sulphur-doped sodalite mineral of Na8Al6Si6O24(Cl,S)2 that is computationally investigated for the first time, in order to understand its photochromic properties that are based on point defects. By combining periodic boundary conditions and embedded cluster-type approaches, we bring a theoretical overview on the photochromism mechanism. Our TD-DFT calculations of sodalite systems containing electrons trapped into chlorine vacancies (called F-center) showed absorption spectrum and a simulated color in agreement with experiment. This modelling highlights the huge effects of F-center?s environment such as the direct contribution of the ?-cage on the trapped electron and a strong vibronic coupling of the absorption spectrum. Post-Hartree-Fock calculations were also operated on S22--containing systems in order to determine the exact mechanism of coloration and discoloration, supporting that the key step is a direct through space charge-transfer between S22- ion and a chlorine vacancy. The geometry modification induced by this charge-transfer leads to a large electronic reorganization stabilizing the F-center thus explaining the high stability of the colored state of the mineral.[1] [1] A. Curutchet, T. Le Bahers, Inorg. Chem. 56, 414 (2017).

Authors : M. Dinachandra, D M Phase, Anshuman Dalvi
Affiliations : Department of Physics, BITS Pilani-Pilani Campus (RJ-333031), India; UGC-DAE Consortium for Scientific Research, Indore 452001, India; Department of Physics, BITS Pilani-Pilani Campus (RJ-333031), India

Resume : Solid polymer electrolyte films were prepared by mixing PEO-NaI with fine ball milled NASICON particles of NaTi2(PO4)3 [NTP] in the composition 10NaI-90(PEO1-XNTPX) (wt%) by solution casting. After removal of solvent, films were further treated in hot press at 70oC. The resulting free standing films were used for investigation by impedance spectroscopy. The bulk conductivity of the composite increases gradually with the NTP content and attain maximum conductivity ? 3 x 10-6 ?-1cm-1 for X = 0.4 at 40oC. The XRD and DSC results suggest gradual decrease of crystallinity with NTP addition and compliment the enhancement in conductivity. The FTIR spectra suggest no complexation of NTP with the host polymer. X-ray Absorption Near Edge Structure (XANES) spectra for Carbon (C) and Oxygen (O) K edge was obtained. For the compositions x ? 0.1, the O k-edge energy shifts towards higher energy with NTP. However, above this composition, the k-edge energy shows gradual decrease. These result suggest that for lower NTP content samples, the electrical transport should be attributed mainly to ion-chain coupling mechanism, but with the higher NTP content, the ionic migration is likely through NTP crystallites. The C k-edge energy does not exhibit any distinct shift with NTP content. This further suggests that the Carbon in the PEO does not interact with the cation of the salt. Our results suggest that XANES analysis can help in the understanding of ionic transport in polymer composites.

Authors : A.I. Popov (a,b), E.A. Kotomin (a,b), D. Gryaznov (a,b) and J. Maier (b)
Affiliations : (a) Institute for Solid State Physics, University of Latvia, 8 Kengaraga Str., Riga LV-1063, Latvia (b) Max Planck Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany

Resume : The color F centers (electron trapped in the halide vacancy) are very common defects in alkali halides, identified by means of the ESR and optical absorption/luminescence. In particular, their properties in fluorites (CaF2, SrF2 and BaF2) are very well studied and understood in detail. However, the manifestation of similar defects in binary oxides with fluorite structure (CeO2 or UO2) is debated for a long time. Recently, we successfully applied the Mollwo-Ivey rule (correlation between lattice constant and optical absorption energy) to explain similarity of optical properties of the F-type centers in alkali halides, alkaline earth oxides and sulfides with NaCl lattice structure [1]. In this study, we have performed similar comparative analysis of the F-type centers in alkaline earth halides and oxides with fluorite structure supported by detailed analysis of the literature. Special attention is paid to oxygen vacancies in CeO2. Obtained results and conclusions are supported by the first principles calculations of the atomic and electronic structure of defective oxides. [1] Popov, A. I., Kotomin, E. A., & Maier, J. (2010). Nucl Inst Meth B 268, 3084-3089.

Authors : Jong-Ho Lee, Junsung Ahn, Ho Won Jang, Si-Won Kim, Mansoo Park,Hoil Ji, Hyoungchul Kim, Kyung Joong Yoon, Ji-Won Son
Affiliations : J-H Lee, J. Ahn, S.-W. Kim, M. Park, H. Ji, H. Kim, K. J. Yoon, J.-W. Son (High-temperature Energy Materials Research Center, KIST, Seoul 02792, Korea) ; H. W. Jang (Department of Materials Science & Engineering, Seoul National University, Seoul 08826, Korea)

Resume : Strain-induced fast ion conduction has been a research area of interest for nanoscale energy conversion and storage systems. However, because of significant discrepancies in the interpretation of strain effects, there remains a lack of understanding of how fast ionic transport can be achieved by strain effects and how strain can be controlled in a nanoscale system. In this study, we investigated strain effects on the ionic conductivity of Gd0.2Ce0.8O1.9-? (100) thin films under well controlled experimental conditions, in which errors due to the external environment could not intervene during the conductivity measurement. In order to avoid any interference from perpendicular-to-surface defects, such as grain boundaries, the ionic conductivity was measured in the out-of-plane direction by electrochemical impedance spectroscopy analysis. With varying film thickness, we found that a thicker film has lower activation energy of ionic conduction. In addition, careful strain analysis using both reciprocal space mapping and strain mapping in transmission electron microscopy shows that a thicker film has higher tensile strain than a thinner film. Furthermore, the tensile strain of thicker film was mostly developed near a grain boundary, which indicates that intrinsic strain is dominant rather than epitaxial or thermal strain during thin film deposition and growth via the Volmer?Weber (island) growth mode.

Authors : Maximilian Morgenbesser, Stefanie Taibl, Markus Kubicek, Alexander Viernstein, Andreas Limbeck, Jürgen Fleig
Affiliations : TU Vienna, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164EC, 1060 Vienna, Austria

Resume : SrTiO3, a perovskite-type oxide, is one of the best investigated materials in solid state ionics and commonly used as a model material for many studies. The defect model of bulk SrTiO3 is well understood and the conductivity of bulk samples can be tailored by acceptor or donor doping, e.g. with Fe3+ or Nb5+ on the Ti4+ site. However, there are still many problems that have not been understood so far, including the electrochemical behavior of SrTiO3 thin films [1]. Different slightly Fe-doped thin films were prepared by pulsed laser deposition (PLD). The electrical conductivity was measured using Electrochemical Impedance Spectroscopy (EIS) and was found to be near the intrinsic point, independent of the Fe3+ dopant concentration. Measurements in different oxygen partial pressures and for different bias voltages revealed further strong deviations from the bulk behavior. Special attention was drawn to the relation between exact stoichiometry and electrical conductivity. The cation stoichiometry was varied by modifying the target composition, but also by different PLD parameters. A model linking the low conductivity to the stoichiometry of the thin films is presented, highlighting the impact of cation vacancies and the antisite defects on the electrical conductivity of Fe:SrTiO3. 1. Kubicek, M., et al., Resistive states in strontium titanate thin films: Bias effects and mechanisms at high and low temperature. Journal of Electroceramics, 2017: p. 1-13.

Authors : Jongseo Lee, Sangyeon Hwang, Minwoo Ahn, Mingi Choi, Doyoung Byun*, and Wonyoung Lee*
Affiliations : Departments of Mechanical Engineering, Sungkyunkwan University 2066 Seobu-ro, Jangan-gu, Suwon-si, Kyunggi-do, 16419, South Korea

Resume : In the typical solid oxide fuel cell system, the interface of electrode between the electrolyte which is known as triple phase boundaries (TPBs) plays crucial role within the electrode reaction. Many researches focused on the modification of interface to enhance the interfacial reactivity. In this work, the Sm0.5Sr0.5CoO3-? (SSC) nanofiber structure is utilized as an electrode. Nanofiber structure have a great potential to be a next generation electrode structure with advanced properties such as larger surface area, facile gas diffusion, and continuous conduction pathway. However, one-dimensional structure of nanofiber structurally limits the contacts at interface which results in high interfacial resistance and sluggish electrochemical reaction. To overcome the issue, nanocrystalline and nano-wrinkled structure of Gd0.1Ce0.9O1.9 (GDC) functional layer is deposited in hundreds nanometer scale with electrostatic spray deposition technique. The optimized functional layer can reduce 70 % of electrochemical resistance than reference electrode without functional layer. Nanocrystalline and nano-wrinkled structure can provide extended active TPBs with higher density of grain boundaries and additional contacts, respectively. Here, we report the modified nanofiber electrode performs not only the enhanced performance, but also the modified reaction mechanism which can be confirmed by reduced activation energy from 1.63 to 1.31 eV substantiating that the interfacial issue is fully relieved.

Authors : Arbi FATTOUM, Amira SENDI, Alessandra CARBONE, Rolando PEDICINI
Affiliations : RU: Materials Environment and Energy, faculty of sciences of Gafsa, Sidi Ahmed Zaroug 2180 Gafsa, Tunisia; CNR-ITAE,Polymer Electrolyte Fuel Cells and Hydrogen Storage, S. Lucia sopra Contesse, 5 - 98126 Messina, Italy

Resume : In this work we investigated the effect of clay addition on various properties of proton conducting membranes of sulfonated polyether ether ketone) (sPEEK) for fuel cell application. We prepared our membranes by Doctor-blade casting technique including different loadings of two types of clay, a commercial montmorillonite and a home purified one, in the range of 5-20 wt%. We performed XRD, ion exchange capacity (IEC), water uptake (WU) and ionic conductivity measurements at various temperatures. The XRD patterns show the typical peaks of the clay confirming the effective introduction and the stability of the clay even after the thermal and the acid treatment of the membranes. The IEC measurements showed increased values by introducing the clay at around 5 wt% and a progressive reduction occurs with the increase of the clay amount. The WU reported at different temperatures showed different behaviours depending on the clay used. At 30° C and for the home clay, we observed a slight decrease in the WU value around 5Wt% and the values remain as a constant for all the superior amounts. At 80°C lower values than sPEEK sample are visible with the 5 and 15wt% while a slight increase occurs with the 10wt%. At 95°C the composite membrane having 5wt% of clay has the highest WU but a reduction is recorded by increasing the amount up to 15wt% and a further increase is visible with the 20wt%. For the commercial clay the behaviour at 30°C is the same but by increasing the temperature at 80°C we observe an increase in the WU with using 5 and 10 wt% and a successive reduction by increasing the loading up to 20wt%. At 95°C the trend is the same for both clays with the highest WU for 20wt%. the proton conductivity of composite membranes carried out at 100%RH as a function of temperature showed increased values with the increase of temperature up to 95°C and a drop at 120°C occurs due to the swelling effect that degrades the polymeric matrix and produces the drop of mechanical properties. The proton conductivity of the sPEEK is the highest in the whole range of investigated temperature and the introduction of clay reduces the conductivity. By comparing the evolution of proton conductivity of composite membranes containing various amounts of clay we observe a reduction at 60°C for 5, 10 and 20wt% only for the commercial clay composite and this trend is not observed for the home purified clay composite for which the conductivity increases until 95°C. As a conclusion of this work we found that the 15wt% loading permits the best compromise between chemical-physical and electrochemical data and for this it will be considered for our future fuel cell tests.

Authors : Natalia Porotnikova (a, b), Lev Putilov (a), Vadim Eremin(a, b), Anna Khodimchuk(a, b), Maxim Ananyev(a, b)
Affiliations : (a) Institute of High Temperature Electrochemistry, Laboratory of Solid Oxide Fuel Cells, Russia (b) Ural Federal University named after the first President of Russia B.N.Yeltsin, Russia

Resume : Study of physical and chemical properties of polycrystalline oxide materials requires consideration of properties related to the grains and boundaries between them. Isotope exchange method provides the necessary information on the kinetics of oxygen exchange with the oxide surface as well as the diffusion of oxygen. In this work, the oxygen isotope exchange with dense ceramic material La0.8Sr0.2MnO3±? is studied at a temperature of 850-950 °C and an oxygen pressure of 1 kPa. An approach to the analysis of oxygen diffusion routes in oxide polycrystalline materials based on the model for the GPE experimental data treatment taking into account the oxygen diffusion inside the grains and along the grain boundaries is proposed [1]. It is shown that when the oxygen diffusion coefficient in the grain volume Dgr exceeds the diffusion coefficient along the grain boundaries Dgb, the rate is determined by diffusion in the bulk of the grains. In this case, we can use the model of Klier et al [2]. In the case when the diffusion coefficient of oxygen along grain boundaries Dgb significantly exceeds the diffusion coefficient in the grain volume Dgr, it is possible to calculate two diffusion coefficients of oxygen using the developed model. The proposed approach is tested on experimental data on a polycrystalline oxide La0.8Sr0.2MnO3±?. The diffusion coefficients in the volume and along the grain boundaries are calculated. The value of Dgr agrees with the data of isotope profiling from literature. References: [1] L. Putilov, M. Ananyev. Abstr. SSI. 2015. D.2.20 [2] J. Phys. Chem. Sol. 27 (1966) 1087-1095 Acknowledgements: This work is partly financially supported by Scholarship of Russian President 2018-2020. The facilities of the shared access center ?Composition of Compounds? IHTE UB RAS were used in this work.

Authors : Maximilian Schaube, Rotraut Merkle, Joachim Maier
Affiliations : MPI for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany

Resume : The incorporation reaction of oxygen into oxide materials proceeds via a complex network of reaction steps, and is expected to depend on the concentration of ionic (e.g. oxygen vacancies) as well as electronic defects (electrons, holes, mixed valent cations), see e.g. [1, 2]. Oxygen exchange is investigated by pulsed oxygen isotope exchange [3] on single and co-doped ceria containing 0.6-20 mol% of dopants: Gd3+ leading to oxygen vacancies formation, Pr3+/4+ creating oxygen vacancies and/or redox activity, and Nb5+ causing the formation of conduction electrons and/or oxygen interstitials. The equilibrium exchange rates are found to be low for Nb-doped and Nb/Pr-co-doped ceria. For Gd-doped ceria (GDC), exchange rates are proportional to the concentrations of Gd and oxygen vacancies. The pO2 dependence indicates that oxygen vacancies as well as molecular oxygen species are involved in the rate determining step. Pr-doped ceria (PDC) exhibits a much stronger variation of the exchange rate, emphasizing the importance of redox-active centers. The low formation rate of 16O18O on PDC compared to GDC points to enhanced oxygen vacancy diffusivity in PDC which is further investigated by SIMS. Measurements on Gd/Pr-co-doped ceria are in progress to deconvolute the impact of vacancies and electronic defects. [1] I. Riess, Solid State Ion. 2015, 280, 51. [2] M. M. Kuklja et al., Phys. Chem. Chem. Phys. 2013, 15, 5443. [3] H. J. M. Bouwmeester et al., Phys. Chem. Chem. Phys. 2009, 11, 9640.

Authors : Virginia Wilde¹, Lana-Simone Unger², Matthias Meffert¹, Lukas Grünewald¹, Heike Störmer¹, Stefan Wagner², Ellen Ivers-Tiffée², Dagmar Gerthsen¹
Affiliations : ¹Karlsruhe Institute of Technology (KIT), Laboratory for Electron Microscopy (LEM), Engesserstraße 7, 76131 Karlsruhe, Germany; ²Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-WET), Adenauerring 20b, 76131 Karlsruhe, Germany

Resume : (Ba?.?Sr?.?)(Co?.?Fe?.?)O? (BSCF) shows very high oxygen permeability [1], which makes it a promising material for oxygen separation membranes. However, secondary phases form at application-relevant temperatures below 850 °C, which degrades the oxygen permeability. One approach to stabilize the cubic BSCF phase is partial substitution of B-site cations. In this work Ti and Nb were investigated regarding their ability to suppress secondary phase formation. Our study focuses on microstructure of doped BSCF in dependence of temperature, doping level and 5% under-stoichiometric B-site occupation. Ti- and Nb-doped BSCF bulk samples were annealed at 600 °C, 700 °C and 800 °C for 10 days. Microstructural characterization was performed using scanning (transmission) electron microscopy in combination with energy dispersive X-ray spectroscopy for chemical analysis. The volume fraction of secondary phases (cobalt oxides, hexagonal BSCF, Ba???Co?O????(Co?O?) precipitates (BCO), Nb-rich precipitates) varies strongly as a function of Ti- and Nb-doping concentration and annealing temperature. Doping with 10% Ti or Nb reduces BCO and hexagonal phase formation. 5% B-site deficiency reduces the volume fraction of cobalt oxide precipitates, which act as nuclei for hexagonal BSCF formation. Most efficient in secondary phase suppression is substitution of 10% B-site cations by Nb in combination with 5% B-site deficiency. [1] Z. Shao et al., Journal of Membrane Science, 172 (2000) 177-188

Authors : E. Pikalova (a.b), M. Koroleva (c), A. Kolchugin (a.b), D. Osinkin (a.b), J. Lyagaeva (a.b)
Affiliations : (a) Institute of High-Temperature Electrochemistry, UB RAS, 620137, Yekaterinburg, Russia; (b) Ural Federal University, 620002, Yekaterinburg, Russia; (c) Institute of chemistry, Komi SC UB RAS, 167982, Syktyvkar, Russia;

Resume : The members of BaCe(Zr)O3 series of proton-conducting electrolytes possess high values of total and proton conductivity and good stability at the intermediate Zr content. The aim of this work was to investigate the electrochemically activity and long-term stability of air electrodes based on the Ca3Co4O9?? compound, well known for its excellent thermoelectric properties and resently proposed as a perspective SOFC cathode material, in contact with Y or Gd doped BaCe(Zr)O3 electrolytes. Particular attention was paid on the effect of the electrolyte composition, kind and amount of sintering aids and shunt effect of the electron conductivity in the electrolyte in oxidative conditions on the electrode performance. The Ca3Co4O9?? electrodes with a precious?metal-free collector developed in this work showed good adhesive properties and superiour polarization characteristics, which were measured on the symmetrical cells with dirrerent proton-conducting electrolytes (ASR values were equal to 0.14 ? 0.22 ? cm2 at 700 C). The most advantageous electrode-electrolyte pairs with an optimized sintering aid?s content were tested in wet air, at 700 oC during 1500 h. Testing of the electrodes in the SOFC-mode was successfully performed on the anode-supported single cells with BaCe0.8Gd0.2O3-? and BaCe0.5Zr0.3Y0.2O3-? thin film electrolytes (30 ?m). This work was supported by the UB RAS program, project 15-20-3-15.

Authors : Jiratchaya Ayawanna1*, Nattapol Laorodphan2, Kamonwan Ruangsrijan2
Affiliations : 1 School of Ceramic Engineering, Suranaree University of Technology, Muang, Nakhon Ratchasima 30000, Thailand; 2 Department of Industrial Chemistry and Textile Technology, Faculty of Science, Maejo University, 63 Moo 4, Nongharn, Sansai, Chiang Mai 50290, Thailand.

Resume : In this work, BaO?SiO2?B2O3 glass with 5 ? 25 wt% of Bi2O3 are prepared by melt?quenching technique. The structure of Bi2O3?containing glasses is studied as a function of Bi2O3 content by IR spectra. Thermal properties of the glasses are obtained by dilatometer. Joining and crystallization of Bi2O3?containing glass sealants with solid oxide fuel cell electrolytes after test for 30 h at 800°C are investigated via both XRD and SEM?EDS. The thermal?mechanical stability of sealing interface is tested via thermal?quenching cycles from room temperature to 800°C for 30 times. The local structure of BaO?SiO2?B2O3 glass is totally changed with the addition of Bi2O3. Bi2O3 has a big effect on reducing a glass?transition temperature and a softening point, but maintains thermal expansion coefficient of BaO?SiO2?B2O3 glass. Barium aluminate (BaAl2O4), bismuth boron oxide (Bi45BO69) and unknown phases are crystallized in only 10 and 15 wt% Bi2O3?containing glasses. SEM micrographs reveal the presence of needle?like, rectangular, and irregular shape crystalline phases and remaining amorphous phase in all samples. The presence of irregular shape Ba?Bi aluminosilicate phase results in crack formation through and surround the crystals. The sealing interface remains intact although the crack propagation is observed after thermal cycles for 30 times. The possible mechanism on the phase evolution of the Bi2O3?containing glass?ceramics at the sealing interface is investigated and proposed.

Authors : Chrysanthi Patriarchea 1,2 , M. Moschogiannaki 1,2,* M. Charalampakis,1,2, SophiaTsoumachidou 4, Ioannis Poulios 4, G. Kiriakidis1,2 V. Binas1,2
Affiliations : 1. Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, 100 N. Plastira str., Vassilika Vouton, 70013 Heraklion, Crete, Greece 2. University of Crete, Department of Physics, 710 03 Heraklion, Crete, Greece 3. Crete Center for Quantum Complexity and Nanotechnology, Department of Physics, University of Crete, 71003 Heraklion, Greece 4. Laboratory of Physical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece *presenter **corresponding author:

Resume : The heterogeneous photocatalytic degradation of para-aminobenzoic acid (PABA), one of the components that are present in many types of PPCPs, has been investigated in aqueous solutions of Zinc oxide nanospheres using UV and Visible illumination. Zinc Oxide (ZnO) nanospheres were synthesized by an easy and low temperature method. ZnO was successfullly synthesized by an thermal aging process under 70oC for 1 hr using Zn acetate, distilled water and oxalix acid as precursors. The final powders was characterized by X-Ray powder diffraction technique, Field-Emission Scanning Electron Microscope and Uv-Vis Spectrometry and showed that pure ZnO is obtained and the morphology is spheres with diameter less than 50nm. ZnO spheres were also studied for photocatalytic degradation of PABA (para-aminobenzoic acid), under UV and Visible illumination. Optimal experimental conditions were 1gr/L of ZnO nanopowder in 20ppm PABA aqueous solution and 90% degradation was obtained under UV irradiation

Authors : Kousika Anbalagan, Tiju Thomas
Affiliations : Department of Metallurgical and Materials Engineering, IIT Madras.

Resume : Application specific morphology tuning of materials is essential for several engineering applications. Ceramic materials which are normally prepared as powders have to be consolidated and heat treated (sintered) to get the final product. To achieve critical control over morphology, the happenings at the initial stages of sintering and particle interfaces are important. These events can be studied by Molecular Dynamics (MD). MD requires the interaction between the atoms as input which will normally be given as interatomic potential. Bond valence (BV) method which has been proposed based on Pauling?s 2nd rule is applicable for all types of bonding. BV based Morse potential is relevant for ceramics which usually have mixed type of bonding. Barium tantalum oxynitride (BaTaO2N), a ceramic which finds use in photoactive and charge storage applications, has been modelled using the above mentioned potential along with the explicit addition of a Columbic repulsion interaction. The lattice parameter and bulk modulus predicted through computation are found to be in agreement with experimental values. Two particle model of BaTaO2N has been modelled using MD and found to have interesting observations. For particles size > 10nm, segregation of TaO phase at the interfaces has been observed which is in agreement with the experimental reports. And also, it is found that for particle sizes < 6nm, phase segregation and degassing of atoms are averted. Based on the above results, we extend our work on MD of BaTaO2N to multiparticle sintering model to study the actual sintering experiments; the resulting densification and morphological changes have been experimentally verified. BV based Morse potential plus Coulomb repulsion term has been proposed for modelling other complex ceramics (eg. oxynitrides) using MD.

Authors : Binod Subedi 1, Josh Shipman 1, Brian Riggs 1, Zhe Wang 2, Christopher Green 3, Greg Lutz 3, Bryan Bilyeu 2, Scott M. Grayson 4, Douglas B. Chrisey 1
Affiliations : 1 Department of Physics and Engineering Physics, Tulane University, New Orleans, LA? 2 Xavier University, New Orleans, LA? 3 Louisiana State University, Baton Rouge, LA? 4 Department of Chemistry, Tulane University, New Orleans, LA

Resume : Sustainable Economic Aquaculture From Autonomously Real-time Monitoring (SEA-FARM) requires a large-scale energy storage device capable of cycling 100% of its energy for a near infinite number of times. Dielectric capacitive storage provides the necessary power density and lifetime, but falls short when it comes to gravimetric energy storage. Ferroelectric ceramics have high dielectric constant, and polarization values but low breakdown field, while polymers have a low dielectric constant but high breakdown strength. The obvious solution is to make a composite of the two materials. However, in practice this has been difficult to obtain. The issue lies at the interface between ceramics and polymers which is natural incoherent, creating an array of defects. By modifying the interface using processes like polymer grafting, these defects can be eliminated. We use a thiol-alkene click chemistry approach to improve the gravimetric energy storage of dielectric capacitors. By designing a thermally and electronically stable polymer that is cured through UV processing, functionalized high dielectric constant nanoparticles are directly bonded into a high breakdown polymer matrix. We show that correctly chosen surface functionalization could dramatically increase the energy storage available in a dielectric capacitor by reducing the energy of free electrons. The nanocomposite formed has a higher breakdown and dielectric constant enhancing the energy density of the capacitors, making a superior dielectric.

Authors : Thi Lan Tran, Hung Tai Nguyen, Dang Thanh Nguyen, Eui-Chol Shin, J.Maier, Jong-Sook Lee
Affiliations : Chonnam National University, Chonnam National University, Chonnam National University, Chonnam National University, Max Planck Institute for Solid State Research, Chonnam National University

Resume : Polycrystalline ZnO with double Schottky barriers at grain boundaries allow the ubiquitous application of varistors for surge protection. Admittance spectroscopy, i.e. measurements of conductance and capacitance as a function of temperature can reveal the deep levels in ZnO associated with the transition metal dopants. On the other hand, similarly as TiO2 system, cheap, abundant, and environmentally friendly ZnO system has been long studied as anodes in photoelectrochemical cells for water splitting. Nanostructured ZnO materials have been extensively studied, e.g., since they can be easily produced and the high performance is expected. However, mechanistic understanding is rather difficult to obtain from such studies, as there are many unknowns such as surface structure, reaction sites and area, transport paths etc. This work aims to study the fundamental properties of ZnO photoanodes by using single crystalline samples with well-defined crystallography from the bicrystalline samples previously prepared. Photoelectrochemical properties of these ZnO single crystalline anodes were studied in a lab-made PEC test station. In addition to DC photocurrent measurements wide-frequency range impedance spectroscopy was obtained, in contrast to conventional mono-frequency capacitance measurements for Mott-Schottky analysis. Havriliak-Negami capacitance function is employed to describe the Schottky capacitance affected by the distributed trap levels. Photoelectrochemical characteristics are compared with nanostructured thin film ZnO anodes. Possibility of the diffusion-recombination mechanism for the additional polarization effects, as recently reported for TiO2 nanorod photoanodes, is examined.

Authors : S. Grieshammer, J. Koettgen, R. Jalem
Affiliations : Helmholtz-Institut Münster, Forschungszentrum Jülich GmbH; Institute of Physical Chemistry, RWTH Aachen University;

Resume : Quantum chemical methods, such as density functional theory (DFT), have become a useful tool to predict structural and electronic properties of solid state materials as well as the migration paths of the ionic charge carriers. In ideal materials with dilute concentration of charge carriers the macroscopic ionic conductivity can be derived directly from the microscopic ion motion. However, at non-dilute concentration the motion of ions is correlated and depends on the local environment, which could be influenced not only by the interaction of the charge carriers but also by the presence of dopant ions and other lattice defects. In this case the ionic conductivity is determined by the correlated motion of all charge carriers, which can be simulated by the Kinetic Monte Carlo (KMC) method. In this study we perform KMC simulations for different solid state materials with potential applicability as electrodes or electrolytes in batteries and fuel cells. The simulations are based on DFT derived migration and interaction energies, which are used to model the energy landscape for the migrating ions. The simulations comprise materials with oxygen, lithium or sodium ions as charge carriers. Ionic conductivities are obtained for various compositions and temperatures and the underlying migration mechanisms as well as the influence of defect interactions are evaluated. The simulation results can contribute to a deeper understanding of the transport properties and support their optimization.

Authors : Edith Bucher (1), Christian Berger (1), Christian Gspan (2), Alexander Menzel (3), Werner Sitte (1)
Affiliations : (1) Montanuniversitaet Leoben, Chair of Physical Chemistry, Franz-Josef-Straße 18, Leoben, Austria; (2) Institute for Electron Microscopy and Nanoanalysis (FELMI), Graz University of Technology & Graz Center for Electron Microscopy (ZFE), Austrian Cooperative Research (ACR), Steyrergasse 17, Graz, Austria; (3) University of Innsbruck, Institute of Physical Chemistry, Innrain 80-82, Innsbruck, Austria

Resume : Long-term degradation of the oxygen exchange activity of mixed conducting perovskite-type air electrodes is a key problem which limits the broad market introduction of solid oxide fuel cells (SOFCs) and solid oxide electrolyser cells (SOECs). Typical degradation mechanisms involve surface reactions with critical impurities (SO2, Cr, Si) and formation of inactive phases. Recently, the Sr-free material Pr0.8Ca0.2FeO3-? (PCF82) was shown to exhibit very fast oxygen exchange kinetics [1]. The present study investigates the long-term stability of PCF82 under ideal (O2-Ar atmosphere) and accelerated ageing (O2-Ar with 2 ppm SO2) conditions. In pure O2-Ar atmosphere PCF82 shows excellent stability of the chemical surface exchange coefficient of oxygen kchem = 6E-4 cm/s for 1000 h at 700°C. Due to the addition of 2 ppm SO2 only a moderate degradation occurs with kchem decreasing to 1E-4 cm/s during 1000 h. Results from post-test analyses by scanning (transmission) electron microscopy and X-ray photoelectron spectroscopy show S-rich secondary phases in the near-surface region. These inactive phases occur in relatively large but locally isolated crystals, whereas significant amounts of the surface area remain unaffected. The latter effect explains the high stability of the oxygen exchange kinetics of PCF82 against SO2-poisoning. [1] C. Berger, E. Bucher, A. Windischbacher, A.D. Boese, W. Sitte, Journal of Solid State Chemistry 259 (2018) 57.

Authors : Jana P. Parras
Affiliations : RWTH Aachen University, Institut of Physical Chemistry, Landoltweg 2, 52074 Aachen, Germany

Resume : Density functional theory (DFT) calculations within the generalized gradient approximation (GGA) were used to examine the behaviour of point defects in the cubic B(VI)O3 perovskite-type oxide, ReO3. Energies of reduction and of hydration were calculated, and the results are compared with literature data for ABO3 perovskite oxides. The activation energies of migration for O2?, H , Li , Na , K and H3O were also determined. The empty A site in ReO3 is found to be detrimental to oxide-ion migration by a vacancy mechanism as well as to proton migration by a Grotthuss mechanism. Na , K and H3O exhibit activation energies of migration higher than 2 eV, whereas Li is characterised by a very low migration barrier of 0.1 eV. Reasons for this behaviour are discussed. Our results suggest that H , O2?, and especially Li , are high mobile ions in ReO3. In general, our results have strong implications for the mechanisms of ion migration in ABO3 perovskite oxides.[1] Literature: [1] J. P. Parras, A. R. Genreith-Schriever, H. Zhang, M. T. Elm, T. Norby and R. A. De Souza, submitted.

Authors : Alexander Schmid, Ghislain M. Rupp, Jürgen Fleig
Affiliations : Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, Vienna, 1060, Austria

Resume : In the search for high performance solid oxide fuel cells cathodes, understanding the mechanism and the limiting parameters of the oxygen exchange reaction is of great importance. Gas phase oxygen and point defects in the electrode are involved in these reactions. The defect concentrations, however, depend on electrode polarization as well as on oxygen partial pressure. The resulting complex relations between electrode polarization, pO2 and defect concentrations make it challenging to mechanistically analyze current voltage curves in terms of reaction orders. In this contribution we show how to take advantage of these interdependencies to separate the kinetic effects of gas phase oxygen and point defects. Counter-balancing pO2-induced defect concentration changes by applying a DC voltage allows studying the pO2 dependency of oxygen incorporation and evolution rates at constant defect concentrations. In a similar way, we use DC voltage to tune the defect concentrations while keeping the oxygen partial pressure constant. Applying this method of data analysis to current voltage measurements on thin La0.6Sr0.4FeO3-d films strongly suggests electron holes and oxygen vacancies as the rate limiting defects for the oxygen evolution and incorporation reactions respectively. A linear relation between oxygen incorporation rate and oxygen partial pressure suggests involvement of molecular oxygen species in the rate limiting step.

Authors : Thuy Linh Pham, Hung Tai Nguyen, Thi Lan Tran, Ji Haeng Yu, Jong-Sook Lee
Affiliations : Chonnam National University, Chonnam National University, Chonnam National University, Korea Institute of Energy Research, Chonnam National University

Resume : Dual-phase membranes of the percolating mixed-conducting oxides LSCF or LSM as an electronic conductor in GDC as an oxygen ion conductor matrix are under active development. Electrical conductivity relaxations have been used for the determination of chemical diffusivity and surface reactivity which determines the kinetics for the high performance oxygen transport membranes. Unlike conventional bar-shape samples for 4-probe conductivity, van der Pauw method applied to the disk samples in this work allows a systematic investigation on the effects of catalytic surface layers such as LSC. Conductivity relaxations were monitored upon change in the atmosphere between air and nitrogen. Instead of applying the solutions of the diffusion equation for the single phase which have issues, it is suggested to examine the Laplace-Fourier transform of the relaxation in time domain to the frequency domain as previously suggested by Boukamp et al. Frequency domain transformation had been made for the relaxation in Hebb-Wagner polarization cells and for pneumatochemical relaxations in hydrogen storage kinetics. Modification of the diffusion problems can be much easily and comprehensively performed using the transmission line models. Preliminary analysis using the relaxation time constants roughly estimated revealed that the relaxations generally faster in oxygen incorporation than in ex-corporation. They are found fastest at the LSCF threshold or conductivity threshold around 20 vol.%, while the slowest at the GDC concentration threshold or ionic conductivity threshold at 80 vol.% LSCF. The LSC coating is found to accelerate the kinetics, especially with oxygen excorporation.

Authors : Hung Tai Nguyen, Dang Thanh Nguyen, Thuy Linh Pham, Jong-Sook Lee
Affiliations : Chonnam National University

Resume : For the highly non-stoichiometric BaBiO3-? electronic structure, conduction mechanism, oxygen non-stoichiometry and phase transitions are supposed to be closely related but overall understanding is not yet achieved. In this work, BaBiO3 was prepared from BaCO3 and Bi2O3 by a solid state reaction method. The sample was pressed into pellets and sintered at 800oC for 24 hours. Two types of electrodes (gold and silver) were applied. AC response of BBO bulk sample was measured for a wide range of temperature by using an electrical furnace, a heating stage and a cryostat. The dielectric and conductive properties indicate the characteristic transitions at the temperatures some of which correspond to the known structural phase transitions, which appear to be closely linked to the oxygen non-stoichiometry. Detailed examination of AC behavior in different temperature regions is expected to provide a valuable insight into conduction mechanism in relation to the phase transition and oxygen nonstoichiometry. Temperature-dependent conductivity is however poorly reproducible. X-ray diffraction showed the presence of cubic perovskite single phase in as-prepared samples in air but annealing in argon results in the distorted structures. Electrical properties are affected by the atmosphere even at low temperatures near room temperature. Indeed, clear mass relaxations were observed by TG even at room temperature. Chemical diffusivities are estimated from the mass relaxation behaviors of powder samples which can be compared to the conductivity relaxations of the bulk samples.

Authors : A.I. Ryskin*, A. Lushchik**, P.P. Fedorov***, N.T. Bagraev****, E. Vasil?chenko**, E. Shablonin**, I. Kudryavtseva**, T.V. Kuznetsova*****, Yu.M. Yarmoshenko*****, A.E. Angervaks*
Affiliations : *ITMO University, 49 Kronverksky Pr., 197101 St. Petersburg, Russian Federation; **Institute of Physics, University of Tartu, 1 W.Ostwald Str., 50411 Tartu, Estonia; ***Prokhorov General Physics Institute, 38 Vavilov Str., 119991 Moscow, Russian Federation; ****Ioffe Institute, 26 Politekhnicheskaya Str., 194021 St. Petersburg, Russian Federation; *****Miheev Institute of Metal Physics, 18 Sofia Kovalevsky Str., 620137 Ekaterinburg, Russian Federation

Resume : High-temperature lability of anion sublattice underlying the superionic conductivity is a characteristic feature of the crystals with fluorite structure. The data on coherent diffuse quasi-elastic neutron scattering show that strong anion sublattice disordering in a superionic state results in the formation of short-lived clusters containing anion interstitials and vacancies as well as displaced anions. Since the formation of cluster is connected with the dynamical disordering of anion sublattice, their existence at room temperature seems impossible. It has been revealed recently that the preheating to 600-1000°C and subsequent quenching of CaF2 single crystals induces the structured absorption in VUV-UV spectral range with a giant low-energy tail reaching the visible region [1]. Such absorption cannot be ascribed to local centers, while similar absorption spectra are typical for indirect semiconductors. In our opinion, the observed absorption is due to the clusters with radically reconstructed electron structure, with regard to that of a regular CaF2 lattice. The disordering of anion sublattice in preheated/quenched crystals manifests itself via color center formation under weak X-irradiation, while X-rays do not affect as-grown crystals. The similar clusters have been observed in SrF2 and BaF2 crystals as well. [1] A.I. Ryskin, P.P. Fedorov, N.T. Bagraev, A. Lushchik, E. Vasil?chenko, A.E. Angervaks, I. Kudryavtseva, J. Fluor. Chem. 200 (2017) 109-114.

Authors : Matthäus Siebenhofer, Tobias Huber, Alexander Schmid, Jürgen Fleig, Markus Kubicek
Affiliations : Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, Vienna, A-1060, Austria

Resume : Materials which change their defect chemistry with the oxygen partial pressure p(O2) are important materials for solid oxide fuel cells (SOFCs) or as sensors. Exact characterization of these materials over a large p(O2) range is desired in this field of research. Since properties such as oxygen non-stoichiometry and defect chemistry have a big influence on ionic and electronic conductivities, electrode design highly depends on how these properties change with different parameters like temperature and oxygen partial pressure. While p(O2) values from 1 to ~10-4 bar (gas mixing with O2) and ~10-20 to ~10-25 bar (mixing of H2 and H2O, p(O2) depending on the temperature) can be rather easily achieved, the range in between is very difficult to access. With inspiration from literature, an optimized high temperature measurement setup was constructed, which electrochemically pumps oxygen through an yttrium-stabilized zirconia (YSZ) tube to change the p(O2) inside the tube accordingly. With this setup, the range from 1 bar to way below 10-30 bar was successfully reached with excellent long-term stability. Impedance spectroscopy and 4-point Van-der-Pauw measurements were conducted to investigate the influence of p(O2) on the defect chemistry as well as oxygen exchange parameters (via fast p(O2) jumps) for lanthanum strontium ferrite La1-xSrxFeO3-? (LSF) and neodymium nickelate Nd2NiO4 ? (NNO).

Authors : Markus Kubicek, Herbert Hutter, Jürgen Fleig
Affiliations : Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, Vienna, A-1060, Austria

Resume : Mixed ionic and electronic conducting (MIEC) perovskite oxides are important materials for energy applications such as solid oxide fuel cells (SOFCs). La0.6Sr0.4CoO3-? (LSC) is a highly active material for the oxygen reduction reaction. Introduction of lattice strain is a very powerful tool to further improve the oxygen ionic conductivity and the catalytic properties of the surface of LSC far beyond compositional optimization. In this work, LSC thin films were deposited by pulsed laser deposition on single crystalline substrates. By using different substrates, columnar polycrystalline thin films (MgO, yttria stabilized zirconia) and epitaxial thin films with either in-plane compressive strain (LaAlO3) or with in-plane tensile strain (SrTiO3) were deposited. Subsequently, oxygen isotope (18O) exchange experiments followed by ToF-SIMS profiling were used to establish highly resolved isotope maps and depth profiles for across-plane and in-plane geometry. Combining the measurements of the tracer diffusion coefficients gives important insight into the different influences of strain and grain boundaries on the concentration and mobility of oxygen vacancies in different directions of LSC thin films. While the oxygen vacancy concentration varies depending on the imposed strain, the hopping distance as well as grain boundary effects are different in-plane and across-plane for the same strain state.

Authors : R.Pascu1, G. Epurescu1, R. Radu2, A.Vlad1, A. Matei1
Affiliations : 1. National Institute for Laser, Plasma and Radiation Physics, Atomistilor Str. 409, P.O. Box MG-36, 077125, Magurele, Bucharest, Romania 2. National Institute for Materials Physics, Atomistilor Str.405A, P.O. Box MG7, 077125, Magurele, Bucharest, Romania

Resume : Samaria - Doped Ceria thin films (Sm0.2Ce0.8O2-?) are studied as solid electrolytes having much higher ionic conductivity than yttria ? stabilized zirconia (YSZ) and gadolinia- doped ceria (CGO) electrolytes operating in intermediate temperature range 400 to 700 degrees. The study is focused on applications in micro-solid oxide fuel cells (µSOFC) and ? sensors. The selection of PLD control parameters were optimized to deposite dense, free cracks of SDC thin films on Si and quartz substrates at 500 degree. The morphology, structure and chemical composition of the obtained films were investigated by SEM, XPS and XRD techniques. Optical characterization was performed using Spectroscopic Ellipsometry and UV-VIS measurements. The electrical properties are measured at 400 degree in air. Key words: SDC thin films; PLD, µSOFC, oxygen sensors

Authors : Pjotrs A. ?guns (ab), Andrei V. Ruban (bc), Natalia V. Skorodumova (ab)
Affiliations : a) Department of Physics and Astronomy, Uppsala University, Box 516, 75121 Uppsala, Sweden b) Department of Materials Science and Engineering, KTH Royal Institute of Technology, 10044 Stockholm, Sweden c) Materials Center Leoben Forschung GmbH, A-8700 Leoben, Austria

Resume : We present the DFT calculations of elastic moduli of \ce{CeO2-Gd2O3}, viz. \ce{Ce$_{1-x}$Gd$_{x}$O$_{2-x/2}$} (CGO), considering both essentially random and C-type ordered oxygen---vacancy configurations, representing fluorite-like and C-type solid solutions, respectively. We show that fluorite and C-type phase differ in bulk modulus and elastic constants (e.g., the ground state C-type phase (x>0.27) has larger bulk modulus). This explains experimentally detected non-linearity (Yavo et al., Scripta Materialia 123, p. 86-89) of elastic moduli with concentration.

Authors : S.M. Asadov1; S.N. Mustafaeva2; D.B. Tagiyev1
Affiliations : 1Institute of Catalysis and Inorganic Chemistry, Azerbaijan National Academy of Sciences, AZ-1143, Baku, H. Javid ave.113; 2Institute of Physics, Azerbaijan National Academy of Sciences, Az-1143, Baku, H. Javid ave. 131,

Resume : Ternary layer-chain TlGaS2 and TlInSe2 single crystals exhibit high photo- and roentgensensitivity making them well-suited for photoresistors and roentgendetectors. The study of physical properties of the TlGaS2, TlInSe2 compounds and solid solutions on their base are very important for establishing the relations between their compositions and properties. This offers the possibility of controlling the band gap, energy position of emission bands and electrical conductivity of such semiconductors. The purpose of present work was to investigate the influence of (TlGaS2)1-?(TlInSe2)? solid solutions compositions (x = 0-0.5) on their photo- and roentgensensitivity, ac ? electric, dielectric and optical properties. The single crystals of (TlGaS2)1-?(TlInSe2)? (? = 0?0,5) solid solutions have been grown up. The photoelectric, roentgendosimetric, dielectric and optical characteristics of the (TlGaS2)1-?(TlInSe2)? solid solutions with various compositions have been determined. The maximum and spectral range of photosensitivity were found to redshift as x increases from 0 to 0.5. Both the photo- and roentgensensitivity of the solid solutions are higher than those of pure TlGaS2. The nature of dielectric losses and the hopping mechanism of charge transport in the (TlGaS2)1-?(TlInSe2)? solid solutions were established from the experimental results on high-frequency dielectric measurements. The results of high-frequency dielectric measurements on obtained (TlGaS2)1-?(TlInSe2)? solid solutions provided an opportunity to evaluate the density of localized states at the Fermi level (NF), the average time of charge carrier hopping between localized states (?), average hopping distance (R), scattering of trap states near the Fermi level and concentration of deep traps (Nt) responsible for ac-conductivity. The temperature dependences of exciton peak position for various compositions (x = 0-0.3) are investigated in 77-180 K temperature interval. It was established that with increasing x in (TlGaS2)1-?(TlInSe2)? solid solutions the width of their forbidden gap decreases.

Authors : Tran Thi Huyen Tran, Thuy Linh Pham, Jinju Song, Sohyun Park, Won Bin Im, Jaekook Kim, Jong-Sook Lee
Affiliations : Chonnam National University

Resume : Understanding the ionic transport characteristics of the electrode materials closely related charging-discharging kinetics has been a long-sought-for but not a quite successful research objective, at least, in the case of many state-of-the-art cathode materials for lithium ion batteries. Superior sodium ion conductivity of NASICON structure should play an important role in the developing Na3V2(PO4)3 as cathode material for sodium ion batteries. With the insight obtained from Na3Sc2(PO4)3 this work aims to investigate the mixed-ionic-electronic conduction in Na3V2(PO4)3 in relation to the reversible thermal phenomena corresponding to order-disorder transitions within the sodium sub-network. Considerable ionic conductivity is evidenced in Na3V2(PO4)3 cathode material in the discharged reference state by the electrode polarization behavior and by the variation with the structural phase transitions similarly as recently observed in Na3Sc2(PO4)3. Therefore, similar sodium order-disorder mechanism for the structural phase transitions can be considered in Na3V2(PO4)3. To understand mixed-conduction better an electron-blocking symmetrical Hebb-Wagner cell is designed using the liquid sodium electrolyte held by the separators between bulk Na3V2(PO4)3 pellet and the sodium metal plates. Wide-frequency range spectra can provide the diffusion kinetics as well as mixed-ionic-electronic conduction characteristics by application of the generalized equivalent circuit for mixed conductors. Temperature dependence will be examined for the limited range due to the stability of the ion-blocking electrode consisting of the liquid sodium electrolyte and sodium metal.

Authors : E.P. Antonova, A.V. Khodimchuk, E.S. Tropin, G.R. Usov, A.S. Farlenkov, M.V. Ananyev
Affiliations : Institute of High Temperature Electrochemistry UB RAS, 620137, Akademicheskaya str. 20, Yekaterinburg, Russia Ural Federal University, 620002, Mira av. 19, Yekaterinburg, Russia

Resume : Electrode kinetics plays an important role in a performance of the electrochemical devices. One of the most common methods for electrode kinetics study is electrochemical impedance spectroscopy. However there is no generally accepted approach to the impedance data analysis, and the choice of an equivalent circuit in each particular case may not be obvious. For detailed analysis it can be useful to measure rates of individual steps of electrode process by an independent method and, applying physical models, to estimate their contribution to the overall electrode impedance. In the present study electrochemical impedance spectroscopy and oxygen isotope exchange with gas phase equilibration methods were applied to investigate the electrode kinetics for the O2, La2NiO4 ? | Ce0.8Sm0.2O1.9 | La2NiO4 ?, O2 symmetrical cells with different electrode thickness and microstructure in the temperature range 600-800 °C and oxygen pressure range 0.2 - 16 kPa. The experiments were carried out in similar conditions in order to get complementary information by the two methods. Using values of oxygen exchange and diffusion coefficients obtained by the oxygen isotopic exchange method the contribution of these processes to the overall electrode impedance was estimated. Probable mechanisms of electrode processes are discussed. The study was financially supported by Russian Science Foundation, project No. 17-73-10196 using facilities of shared access center ?Composition of Compounds? of IHTE UB RAS.

Authors : Hung Tai Nguyen, Thi Lan Tran, Dang Thanh Nguyen, Eui-Chol Shin , Soon-Hyung Kang, Jong-Sook Lee
Affiliations : Chonnam National University

Resume : Full parametric impedance analysis of AC response of a TiO2 photoanode in a PEC cell as a function of the potential and with the illumination condition has been performed, which comprises the depletion capacitance at the semiconductor-electrolyte junction following Mott-Schottky relation and the chemical capacitance in the electrode layer for the electron diffusion-recombination kinetics. All the parameters can be related to the spectral feature and physical interpretation made and implication discussed. Compatibility of the two physical mechanisms for the PEC impedance is to be noted and further examined. Importantly, well-defined Schottky capacitance can be successfully described by employing Havriliak-Negami capacitance function explained by the distributed trapping levels. Bisquert diffusion-recombination model can be applied with chemical capacitance in ideal capacitor elements, not in CPE, thus allowing the straightforward interpretation of the diffusivity and recombination rate constants. Interfacial Warburg impedance closely related to the bulk electrode parameters, is suggested to be generic in many electrochemical systems described by diffusion-recombination (reaction)-trapping mechanism.

Authors : Georgina L. Wellock, Joel Statham, Marco Molinari, Stephen C. Parker, Benjamin J. Morgan
Affiliations : University of Bath, Department of Chemistry, Claverton Down, Bath, BA2 7AY; University of Bath, Department of Chemistry, Claverton Down, Bath, BA2 7AY; University of Huddersfield, School of Applied Sciences, Queensgate, Huddersfield HD1 3DH; University of Bath, Department of Chemistry, Claverton Down, Bath, BA2 7AY; University of Bath, Department of Chemistry, Claverton Down, Bath, BA2 7AY

Resume : The presence of interfaces can strongly affect ionic transport in many energy materials. A key effect is the segregation of charged defects to or from these interfaces, which is accompanied by the accumulation or depletion of mobile ions in adjacent space-charge regions. In materials with interfacial separations on the order of nanometers, space-charges are expected to overlap, producing nano-ionic effects, where mobile ion concentrations deviate from bulk values. This is predicted to cause large differences in ionic conductivities. Analyses of nano-ionic space-charge formation typically use a continuum Poisson-Boltzmann model, under simplifying constraints. This allows analytical solutions for properties such as charge-carrier concentrations to be derived, but these results may be sensitive to the approximations that make this analysis possible. We have used atomistic modelling and a numerical site-explicit 1D Poisson solver to model space charge formation between pairs of parallel grain boundaries in Gd-doped CeO2, a widely studied solid electrolyte with applications in solid-oxide fuel cells. Nanocrystalline Gd-doped ceria has been reported to have an ionic conductivity several orders of magnitude larger than samples with larger grain sizes. Our approach allows us to explicitly include a description of atomic scale structure in our model. We will present results for a range of CeO2 grain boundaries, and compare the resulting data to the predictions from conventional models.

Authors : Soukaina Lamnini 1,2, Zsolt Fogarassy2, Endre Zs. Horváth2, Sára Tóth3, Zoltán Károly4, Eszter Bódis4, Katalin Balázsi 2, Csaba Balázsi 2
Affiliations : 1 Doctoral school of of Material Science and Technologies, Óbuda University, Bécsi str.96/B, 1034 Budapest, Hungary 2 Institute for Technical Physics and Materials Science, Centre for Energy Research, Hungarian Academy of Sciences, Konkoly ? Thege M. str. 29-33, 1121Budapest, Hungary 3 Wigner Research Center, Hungarian Academy of Sciences, Konkoly ? Thege M. str. 29-33, 1121 Budapest, Hungary 4Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences HAS, Magyar Tudósok Körútja 2, 1117 Budapest, Hungary

Resume : Several energetical applications are known where yttria-stabilized zirconia (YSZ) and zirconia / multiwall carbon nanotube (MWCNT) composites were useful used as parts of solid oxide fuel cells (SOFC), photovoltaic solar cells, supercapacitor or hydrogen storage materials. The Ni ? YSZ cermets are widely accepted as anodic materials in SOFCs with high catalitic activity and electrical conductivity. Some research works showed the drawbacks in hydrocarbon fuels as carbon build-up, sulfur poisoning or low tolerance to redox cycling. These irreversible processes damage the microstructure of anodes and reduce the cell performance, therefore Ni-free anode materials are continously researched and developed to overcome these problems. In this work, the design of milled and sintered YSZ / MWCNT composites was studied. The detailed structural investigations confirmed the MWCNT clusters in all cases, while the best homogenization was obtained in the case of YSZ / 1 wt% MWCNT composite. The Raman measurements showed unanimously results with structural observations. The apparition of the G and D bands for all the composites at ~1589cm?1 and ~ 1356cm?1 confirmed the structural integrity of MWCNT after the milling process. The effect of attritor milling and spark plasma sintering (SPS) at 1200°C, 1300°C and 1400°C on the structural and thermo-mechanical properties of 8 mol% yttria-stabilized zirconia (8YSZ) composites with 1wt%, 5 wt% and 10 wt% MWCNTs addition has been investigated.

Authors : Dino Klotz (a, b), Nicola Perry (a, b, c), Harry Tuller (b)
Affiliations : (a) WPI-International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, Japan; (b) Department of Materials Science and Engineering (DMSE), Massachusetts Institute of Technology (MIT), Cambridge, USA; (c) Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois at Urbana-Champaign, USA

Resume : We report a new in situ measurement method to determine the kinetics of the oxygen reduction reaction (ORR) and oxygen incorporation into fluorite and perovskite type mixed conductors, PCO (PrxCe1-xO2-d) and STF (Sr(Ti1-xFex)O3-d). These materials are promising candidates for use as electrodes in SOFC, gas sensors, and oxygen storage materials involving an oxygen exchange reaction. However, the individual rate limiting reaction steps are not fully identified. Optically probing the oxidation state by absorption measurements is feasible for PCO and STF and can help to discern between surface and bulk rate limiting processes. Optical relaxation measurements have been used in the past for this purpose. For our optical impedance spectroscopy (OIS) only a small signal voltage perturbation is applied to pump oxygen in and out of the film electrochemically, thereby changing its absorption. This generalized electrochemical impedance spectroscopy (GEIS) technique comes with the benefits of superior signal to noise ratio and the toolbox of analysis techniques available for impedance data can be readily applied to the acquired measurement data. We will present OIS measurements on model thin films, demonstrate the basic modeling approach and discuss the obtained results. The investigation also includes the electrochemical impedance measured in parallel. We believe that this is a very promising approach to provide answers for some of the most challenging questions in solid state ionics. This work was supported by JSPS Core-to-Core Program, A. Advanced Research Networks.

Authors : B.E.Umirzakov, S.B.Donaev, N.M. Mustafaeva
Affiliations : Tashkent state technical university

Resume : The present work is devoted to the study of the energy and angular dependences of the secondary electron emission (SEE) coefficients, the reflection and absorption coefficients of light by the Ga0.5Al0.5As/GaAs film. Based on the analysis of the obtained results on the structure, emission and optical properties of thin GaAlAs/GaAs films, the following conclusions can be drawn: The band-energy parameters, emission properties and lattice parameters of thin films (d ? 50-100 Å) of GaAlAs obtained by MBE and ion implantation differ little from each other. In the case of films obtained by ion implantation, the crystallographic orientation of the film and the substrate are in good agreement with each other. The depth exit zone of the true-secondary electrons and photoelectron for GaAs is ~ 100-120 Å, and for the Ga0.5Al0.5As film it is 150-160 Å. The values of the coefficients ?, respectively, for GaAs and Ga0.5Al0.5As are practically identical, and the values of the true-secondary electrons coefficients ?m differ by 20-25%. The coefficient of light reflection K in the whole investigated wavelength region (both in the absorption region and in the region of maximum reflection) of GaAlAs was up to 2 times that of GaAs. The heating of the GaAlAs/GaAs system at T ? 600 0C for 5-10 min resulted in a slight decrease in K in the region of intense light absorption (? ? 580 nm). One of the reasons for this may be the presence of some excess Ga or As atoms in GaAlAs films.

Authors : Ingars Lukosevics, Peteris Lesnicenoks, Janis Kleperis
Affiliations : Institute of Solid State Physics, University of Latvia

Resume : As waste material from combustion, CO2 can be used to synthesize some useful hydrocarbons by electrochemical conversion. As theoretical studies have already shown this process could be enhanced by graphene supported copper particles making it possible to synthesize more than 30 different products. However before implementing this procedure in industrial scale certain specifications must be achieved e.g. the durability of the working electrode. In this work graphene sheet stacks (obtained by electrochemical exfoliation from waste graphite crucible) are incorporated into nitrocellulose matrix and copper structures are electrochemically deposited on the composite creating a conductive catalyst coated electrode (CCE) thick films with an average thickness below 40 µm. In addition to surface morphology, electrochemical analysis has been carried out focusing on the durability of prepared electrodes in CO2 saturated aqueous solutions. The cyclic voltammetry tests show that the prepared CCE can be successfully used as cathode material for continuous and sustainable electrochemical processes.

Authors : Wenjing Quan1, Xuefeng Hu1,*, Junwen Qiu1, Wei Du1, Xinjie Min1, Yewei Hu1, Shaohe Lu1, Huishi Chen1, and Wei Zhang1,2,*
Affiliations : 1.State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing, 210009, P.R. China; 2.School of Electrical Engineering & Intelligentization, Dongguan University of Technology, No.1 Daxue Rd, Dongguan, Guangdong Province, 523808, P. R. China.

Resume : Tin dioxide (SnO2), as a n-type semiconductor with the large band energy gap of 3.6 eV at 300K, has appeared to be one of the most popular materials for gas sensing due to its excellent stability, high sensitivity, fast response, etc. Though the morphology, size, and surface permeability of nanomaterials can result in the superior gas sensing compared with their thin films and bulks, their easy-going self-aggregation is the barrier to explore the best performance. So looking for a satisfying approach for the ordered arrangement of nanosized building blocks into hierarchically porous or hollow structures is still attracting widely attention. In addition, doping metal ions, such as Co, Au, Pt, Cu, etc, is another effective way to enhance the gas sensing of metal oxide semiconductors. Here, two categories of novel sensor materials, pure SnO2 with hierarchical pagoda structures and different contents of Pt-doped 3D porous SnO2 with similar structures were synthesized by a hydrothermal method. And the latter, bearing the porous, hierarchical, and dopant effects synchronously, has been systematically examined for acetone gas sensing. As such, the comparative study of both materials and different contents of Pt doping have been performed to show the porous and doping effects in detail, which further indicate that the Pt-doped 3D porous SnO2 hierarchical structure can be optimized as a promising sensing material for the detection of acetone gas.

Authors : Huyen Tran Tran, Jee-Hoon Kim, Eui-Chol Shin, Cheol-Woo Ahn, Dong-Soo Park, Jong-Sook Lee
Affiliations : Chonnam National University, Chonnam National University, Chonnam National University, Korea Institute for Materials Science, Korea Institute for Materials Science, Chonnam National University

Resume : LLZ ceramic power and pellets were prepared by the typical ceramic process. As recently illustrated in detail, conventional brick-layer model is not satisfactory both in theory and in practice for the description of dispersive and overlapped responses of polycrystalline solid electrolytes with current-constriction effects due to the grain boundaries. Parallel networks of the complex dielectric functions have been shown to successfully describe the AC responses of polycrystalline sodium conductors over the wide temperature and frequency range with model parameters of well-defined physical significance only around ten in number. Strongly dispersive impedance response of polycrystalline lithium garnet oxide ionic conductors Li7La3Zr2O12 indicates well-defined capacitance effects where the relaxation behavior suggests the common mobile-charge-carrier origin. An equivalent circuit model with one total sample resistance component connected in parallel with three Havriliak-Negami dielectric functions can succinctly describe the frequency and temperature dependence and also distinguish three components originated from bulk and the current-constriction due to the grain boundaries and electrodes. The low frequency polarization is successfully described by a finite length Warburg impedance with an interfacial Warburg impedance. The transmission line parameters are also found to be closely associated with the bulk conduction mechanism. The feature is suggested to be generic in the electrode polarization of diverse solid electrolytes.

Authors : Yewei Hu1, Xuefeng Hu1,*, Junwen Qiu1, Wenjing Quan1, Wei Du1, Xinjie Min1, Shaohe Lu1, Huishi Chen1, and Wei Zhang1,2,*
Affiliations : 1.State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing, 210009, P.R. China; 2.School of Electrical Engineering & Intelligentization, Dongguan University of Technology, No.1 Daxue Rd, Dongguan, Guangdong Province, 523808, P. R. China.

Resume : NO (Nitric oxide) is a common toxic gas generated by the exhaust of automobile engines and the production of fossil fuel power plants, which seriously endanger the environment and human health. However, as an important intermediate in the chemical industry, NO is a messenger and effector molecule. In addition, as a biomarker gas in some physiological and pathogenic processes, the detection of exhaled NO is a new promising and noninvasive way as well, for instance, in studies of lung diseases and asthma. So researching and developing a portable, low-cost, high sensitivity with a ppb-level, and high selectivity NO gas sensor is an emergent and challenge job. Here, x%wtIn2O3-y%wtNb2O5-WO3 films were deposited by pulsed laser deposition (PLD) as ppb level NO gas sensors. We found that 1% In2O3-1% Nb2O5-WO3 is superior to one element doped and undoped WO3 films. As to 100ppb NO, the 1% In2O3-WO3 film has the sensitivity of 4.1 at the best working temperature of 70?, while 1% Nb2O5-WO3 has the sensitivity of 43.0 at the 110?, which are better than undoped WO3 films with 1.7 sensitivity at 110?. Furthermore, 1% In2O3-1% Nb2O5-WO3 increase the sensitivity to 56.1 at 70? and its limit of detection is 20ppb with the sensitivity of 3.2. Additionally, the sensitivities of 100ppbNO2, 10ppm HCHO, 20ppmCO, 20ppmH2, and 20ppmNH3 at 70? are 2.2, 4.0, 3.7, 3.3, and 2.3, respectively. So, the 1% In2O3-1% Nb2O5-WO3 has the lower working temperature, ppb-level sensitivity, and high selectivity.

Authors : Osiris Escamilla Luna, Fabiola del Carmen Gómez Torres, German Pérez Hernández and Laura Lorena Díaz Flores
Affiliations : Universidad Juárez Autónoma de Tabasco, Av, Universidad s/n Zona de la Cultura Col. Magisterial Villahermosa Centro Tabasco CP 86040 México.

Resume : This work investigates ZnO thick films for gas sensing application. Zinc oxide nanoparticles were synthesised by a mechanochemical method using ZnCl2 and Na2CO3 as precursors and NaCl as a diluent. The ZnO samples obtained were washed with DI water to remove NaCl and thermal annealed at 400 °C for 2 hours. The crystallographic structure of the ZnO synthesized powders was characterized by X-ray diffraction and its structure and morphology using HRTEM and SEM. A viscous screen printing paste, was prepared by dispersion of ZnO synthesised nanoparticles in ethanol/ethylcellulose solution with terpineol as evaporation control agent. By using screen printing method, thick films of synthesized ZnO paste were deposited on glass substrate and sintered at 450°C for 30 minutes. After deposition, the ZnO film thickness was measured and the effects of structural and morphology of ZnO on gas sensing properties were studied. ZnO thick films were exposed to H2S at 20 ppm and the results show that these ZnO thick films have applications as H2S gas sensor.

Authors : Pinar Kaya, Michael Weissmayer, Giuliano Gregori, Petar Yordanov, Wilfried Sigle, Peter A. van Aken, Hanns-Ulrich Habermeier, Joachim Maier
Affiliations : Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany

Resume : In this study, the possibility of modifying the grain boundaries of strontium titanate by decoration has been investigated mainly by impedance spectroscopy and Seebeck coefficient measurements. The findings are discussed in the framework of defect chemistry and microstructure. Grain boundaries in SrTiO3 have been found to be notoriously positively charged, giving rise to a strong depression of p-type (increase of n-type) and even sharper depression of ion conductivity. It is hence of enormous interest to be able to modify nature and charge of the grain boundaries. For that purpose, La and Rb compound were chosen as decorating dopants. In the case of La, donor doping of the grain boundary core and at least of bulk-near regions occurs, depending on the preparation condition. We notice the formation of a secondary grain boundary phase which explains the unusual conductivity features. In contrast to La, the big Rb-ion is expected not to be incorporated and to confer an extra negative charge contribution to the grain boundary core. Indeed this is observed up to 3at.%, while the tendency inverts for larger percentages, indicating Rb then to be introduced interstitially. In the Rb-case the positive core charge is hence reduced, but was not inverted.

Authors : Tobias M. Huber 1,2,3, Richard Schlesinger1, Alexander Schmid1, Markus Kubicek1, Jürgen Fleig1
Affiliations : 1Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, 1060 Vienna, Austria 2 Huber Scientific, Rottmayrgasse 17/29, 1120 Vienna, Austria 3 Next-Generation Fuel Cell Research Center (NEXT-FC), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan

Resume : There are two common methods to measure the impedance response of only one electrode of a solid-state electrochemical cell, microelectrodes or a three-terminal configuration. In aqueous electrochemistry, three-terminal configurations are widely used, however, implementing this method in solid-state electrochemistry is highly non-trivial. This work summarizes, which method is most suitable for different applications. We show potential error sources and evaluate each of them quantitatively with special emphasis on their impact in thin film electrode measurements. Evaluation is done by means of finite elements analysis (FEA), electric circuit simulations and conducted measurements. Three potential error sources were identified as particularly crucial factors: (i) Asymmetric sample cells (ii) short circuit currents across the reference electrode (RE), (iii) Especially for highly resistive electrode, coupling capacitances between the three electrodes. These error sources can result in different measurement errors such as additional high frequency semicircles, additional low frequency semicircles, inductive loops and even more critical, erroneous electrode properties without indicating of additional features in the impedance spectrum. We propose a novel sample geometry, the ?wing geometry?, which was designed to minimize the measurement errors significantly, but still remains affordable and suitable for different applications.

Authors : Daniel Mutter, Daniel F. Urban, Christian Elsässer
Affiliations : Fraunhofer IWM, Freiburg, Germany; University of Freiburg, FMF, Germany

Resume : Solid oxide fuel cell (SOFC) and solid oxide electrolyzer cell (SOEC) devices, which transform chemical into electrical energy and vice versa, have the potential to make a significant contribution to the efforts of overcoming future problems of the energy economy. An optimal functionality of the electrodes in such devices requires a high catalytic activity at their surfaces, i.e. the capability for chemisorption and dissociation of O2 molecules, charge transfer to O2?, and incorporation of O2? ions into vacant anion sites of the crystal structure. Promising materials regarding these requirements are perovskites (ABO3), with La, Ba or Sr ions on the A sites, and transition-metal ions (Mn, Fe, Co) on the B sites. Using density functional theory calculations with a Hubbard-U correction, we aim to shed light on the correlation between stoichiometry, point defect concentrations and experimental synthesis conditions in the perovskite system LaxSr1-xFeyMn1-yO3-d. The stability regions in the phase diagram and point defect concentrations were calculated taking into account image charge corrections. Employing defect equilibrium reactions and applying the charge neutrality condition, point defect concentrations were obtained for varying elemental chemical potentials, i.e., synthesis conditions. The sensitivity of the results on the choice of the Hubbard-U parameter will be discussed.

Authors : Felix Hirschberg, Jens Brüggemann, Hans-Hermann Johannes, Wolfgang Kowalsky
Affiliations : TU Braunschweig, Institut für Hochfrequenztechnik, Schleinitzstraße 22, 38106 Braunschweig, Germany

Resume : Ionic transport is of increasing significance to enable controlled interplay between technical and biological systems. It allows on one hand the realization of novel electronic devices (ionic resistors, transistor, and memristors) and on the other hand direct contacts to biological systems and individual cells with controlled electrochemical potential. Hydrogels like polyacrylamide (PAM) offer attractive properties as ionic transport media with structural biocompatibility. In biomedical applications artificial passive ionic channels of PAM can be used to adjust the ionic transport resistance, ion selectivity and thus ionic flux. Based on the thermodynamic diffusion process of the ions in the hydrophilic channel, the ionic resistance is determined by geometry and polymeric matrix. By applying voltage along the ionic channel the transport of the ions can be supported or restrained by the electrical field with respect to polarity. The incorporation of an ion selective fluorescent dye like N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE) gives information of the transient distribution of chloride ions in the hydrogel channel by fluorescent spectroscopy, since PAM is transparent for excitation and emission. Furthermore, MQAE can be immobilized in the hydrogel and thus determining the transition time of drifting ions through hydrogel channels. Current investigation focus on manufacturing hydrogel microchannels and switchable network matrices.

Authors : Thimo Ferber, ?ahin Cangaz, Sefa Akça, Conrad Guhl, René Hausbrand
Affiliations : Technische Universität Darmstadt

Resume : With the upcoming development of all solid-state batteries, there are solid electrolytes available that reach ionic conductivities of the same level as their liquid counterparts. Solid polymer electrolytes can be combined with inorganic solid electrolytes and electrode materials to composite electrodes which promise high performance and durability. Interfaces in such composites play a crucial role as they contribute significantly to the inner resistance of the cell. PEO is a cheap and easy to process polymer, which already reaches good ionic conductivity at elevated temperatures, and is well suited as model material for interface studies. In this contribution we present results on the interfaces between PEO and LiCoO2 as well as PEO and Li. As interfaces are usually buried within the device, we used a surface science approach to study the interfaces based on model systems. For the LiCoO2/PEO interface investigation, the PEO was evaporated stepwise onto the LiCoO2, a methodology which can also be applied to the study of interfaces between PEO and inorganic solid-state electrolyte. Reaction layer formation takes mostly place at the anodic side, while the cathodic part is less reactive. Degradation is not only limited to the polymer, but also affects the salt, for example LiTSFI. Information gained by this method gives further insight in to the composition of the reaction layer and the origin of the interface resistance.

Authors : Noriko SATA, Feng HAN, Rémi COSTA
Affiliations : Institute of Engineering Thermodynamics, DLR

Resume : Electrochemical cells based on proton conducting ceramics (PCC) offer a number of potential electrochemical applications. Since proton is the ionic charge carrier, they are utilized in electrochemical devices in which hydrogen or hydrogen containing molecules are the main resources or products. It should also be noted that moderate operating temperatures and low partial oxygen pressure on the fuel electrode in PCCs are advantageous to prevent degradation of the components. One of the critical issues in realizing PCC devices, however, is to find promising materials for air electrode that demonstrate high conductivities and chemical stability. In this work, we focus on BaZrO3 based electrode candidates to be applied for PCCs based on Ba(Zr,Ce,Re)O3 electrolytes (Re: trivalent dopant). Powder specimens are synthesized by a conventional solid state reaction process and their fundamental properties, including structural analyses and electrical conductivities, are investigated. Based on the experimental results, their potentials as air electrodes will be discussed.

Authors : Johanna Hackl(1), Tomá? Ducho?(1,2), David N. Mueller(1), Jolla Kullgren(3), Dou Du(3), Caroline Mouls(4), Daniel M. Gottlob(1), Muhammad I. Khan(1), Stefan Cramm(1), Kate?ina Veltruská(2), Vladimír Matolín(2), Slavomír Nem?ák(1,5), Claus M. Schneider(1).
Affiliations : (1) Peter-Grünberg-Institut 6, Forschungszentrum Jülich, 52425 Jülich, Germany; (2) Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 18000 Prague, Czech Republic; (3) Department of Chemistry?Ångstro?m Laboratory, Uppsala University, Box 538, S-751 21 Uppsala, Sweden; (4) Laboratório Nacional de Luz Síncrotron, 13083 Campinas - SP, Brazil; (5) Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Resume : Ceria exhibits unique catalytic properties with numerous applications, ranging from water splitting to oxygen storage. Density functional theory calculations predict a strong dependence of oxygen vacancy formation energies for different CeO2 surface orientations. Particularly, the (100) surface is expected to have a lower oxygen vacancy formation energy than the (111) surface. It has also been shown, that it is possible to grow both (111) and (100) oriented CeO2 islands on Cu (111), by adjusting the Ce and O2 ratio during the growth. In the present work CeO2 islands with (111) and (100) surfaces are simultaneously grown in-situ onto a Cu (111) substrate. The island formation is observed and characterized with low energy electron microscopy (LEEM) and micro-LEED (low energy electron diffraction). Using laterally resolved x-ray absorption spectroscopy (XAS) performed in a photoemission electron microscope (PEEM) the reduction of Ceria in an H2 environment is observed in-situ and in real-time, directly comparing the reduction kinetics of the (111) and the (100) islands. Spectra of the Ce M5 edge show a more pronounced reduction of Ce for the (100) islands as compared to the simultaneously observed (111) orientation, unambiguously showing that the surface orientation of CeO2 has a profound impact on its catalytic properties. A DFT study tailored to the morphologies of ceria islands confirms the observed differences in surface thermodynamics of the different orientations.

Authors : Tynee Bhowmick(a), Sudip Nag(b) and S.B. Majumder(a)
Affiliations : (a)Materials Science Centre, Indian Institute of Technology, Kharagpur; (b)Electronics and Electrical Communication Engineering, Indian Institute of Technology, Kharagpur

Resume : For air quality monitoring thin film type selective sensing elements for volatile organic components (VOC) (1000-5000 ppm), carbon monoxide (CO) (50-1000 ppm), nitrogen dioxide (NO2) (0.1-5 ppm), and hydrocarbons (HCs) (100-1000 ppm) are in large demand. Identification of selective sensing materials for each of these gases remain a major problem as majority of conventional chemi-resistive sensing materials (viz. SnO2, ZnO, WO3 etc) are plagued with relatively higher operating temperature (~ 300oC), poor base-line stability (> 15%) during prolonged uses, cross-sensitivity towards these gases and moisture etc in real field application. In the present work we have demonstrated that chemical solution deposited lanthanum iron cobalt oxide (LFCO) thin films could be attractive candidate for selective CO sensing (in the concentration range between 5 to 500 ppm) at relatively lower operating temperature (175-250oC). Among all these test gases studied, it has been reported that at an operating temperature ~ 225oC, LFCO thin film sensing elements sense only CO gas (5-500 ppm) with a response % varying between 18-87% and response and recovery times varies in the range of 49 – 225 seconds and 94 – 852 seconds respectively. We have explained that the superior CO sensing characteristics of ABO3 type LFCO thin films are primarily governed by the ‘B’ site transition metal ions (Fe,Co). Also, the symmetry and coordination of A (La,Sr) and B site elements are lost on these perovskite surfaces, and as a result, the surface is saturated with adsorbed oxygen and hydroxyl ions. These adsorbed species make the perovskite surface catalytically active and thus, the CO oxidation is favorable at relatively lower operating temperature. A microcontroller based electronic circuit module with LCD display has been developed and the CO sensing characteristics of optimized thin film type LFCO sensing elements have been demonstrated and benchmarked with available commercial CO sensing elements. Keywords: Lanthanum iron cobalt oxide, thin film, carbon monoxide sensing

Authors : Abhishek Ghosh, Subhasish Basu Majumder
Affiliations : Materials Science Centre, Indian Institute of Technology, Kharagpur

Resume : Carbon dioxide (CO2) has a wide variety of manmade and natural applications including but not limited to carbonating drinks, fire extinguishers, photosynthesis etc. However, it is a green house gas, and in atmosphere it absorbs infra-red energy and dissipates the heat to the surrounding to cause global warming. Two most important sources of CO2 in consumer related activities are road transportation and building heating, ventilation and air conditioning (HVAC) systems. In view to this, development of economical, indigenous CO2 monitoring system is highly desirable. It is extremely advantageous to use semiconducting metal oxide (SMO) based thin film gas sensors compare to other commercially available sensors due to low cost, small size, higher stability and selectivity. Some recent literature reports recommend that hetero-junction between ?n? and ?p? type of semiconducting oxide can enhance the response and selectivity of the test gases. But, very few literature reports exist which specify the factors effecting CO2 gas sensing using ?n?-?p? type multilayer thin films. In the present work we have demonstrated CO2 sensing properties and obtained the factors effecting CO2 sensing performance using SMO based hetero-structure multilayer thin film.

Authors : George F. Harrington(a,b,c,d), Lixin Sun(d,e), Nicola H. Perry(c,d,f), Kazunari Sasaki(a,b), Bilge Yildiz(d,e), and Harry L. Tuller(c,d)
Affiliations : (a) Center for Co-Evolutional Social Systems, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan (b) Next-Generation Fuel Cell Research Centre, Kyushu University, 744 Motooka, Nishi-ku Fukuoka 819-0395, Japan (c) WPI-International Institute for Carbon-Neutral Energy Research, Kyushu University, 744 Motooka, Nishi-ku Fukuoka 819-0395, Japan (d) Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139, U.S.A. (e) Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139, U.S.A. (f) Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL 61801, U.S.A

Resume : To date, studies into the effect of strain on the ionic conductivity of thin films and multilayers have focused on the so-called ?optimised? ionic conductors, such as Gd- or Sm-doped CeO2, but the results have been both controversial and inconstant. In addition, very little attention has been payed to the ?non-optimised? electrolytes where defect-defect interactions are much more significant. But as the defect association is much stronger for these materials a much larger modification in the conductivity due to strain may be possible. We have grown ?optimised? and ?non-optimised? doped-CeO2 epitaxial films by PLD on double buffered MgO substrates. The dopants used were La, Gd, and Yb, which represents significant differences in the defect association. The strain was varied by thermal annealing to relax the intrinsic strain occurring during growth. With increasing in-plane compressive strain, the conductivity of the films was reduced and the activation energy increased. The observed change is in excellent agreement with computational work, and consistent with other experimental findings. Furthermore we show that the effect is more pronounced for Yb-CeO2 than La- or Gd-CeO2, demonstrating that larger changes in the conductivity with strain can be obtained with ?non-optimised? dopant cations. We rationalise our findings using static force-field simulations, suggesting that the cause is due to a combination of changes in the migration barrier and vacancy-cation configuration.

Authors : M.M. Asadov, E.S. Kuli-zade
Affiliations : Institute of Catalysis and Inorganic Chemistry, Azerbaijan National Academy of Sciences

Resume : In this work, the phase relationships in the ZnO?PbO?Bi2O3 system are studied by the thermodynamic method and X-ray phase analysis of the samples. Quasi-binary sections were determined and an isothermal cross section of the system was constructed at 298 K. A method for calculating the standard thermodynamic functions of the formed intermediate phases was tested. The thermodynamic characteristics of the ZnO?2PbO?Bi2O3 compound are calculated. For high-temperature oxide phases of the ZnO?PbO?Bi2O3 system, new thermodynamic databases were used by their critical estimation / optimization, taking into account the available experimental data on phase equilibria. A thermodynamic model of solutions was chosen, which reproduces all the phase equilibrium data of the ZnO?PbO?Bi2O3 system within experimental errors. The selected thermodynamic model was used for extrapolation in the temperature and composition region, where experimental data are not available. Thermodynamic calculations of phase equilibrium have been carried out, which are of interest for the preparation and thermal treatment of samples in the ZnO?PbO?Bi2O3 system. Operating conditions usually deviate from thermodynamic equilibrium, and the oxygen potential in the processing of samples is not established. In view of this, the calculated diagrams are intended to give the development engineers data on the trends and changes in the liquidus temperature, the degree of crystallization and the partial pressures of the volatile components as a function of temperature, composition, and oxygen potential. The calculated diagrams can also help identify variable processes in high-temperature oxides, which are important for industrial practice. Calculation and modeling significantly reduces the amount of experimental work that must be performed for optimization of operations.

Authors : Veaceslav Sprincean1, Dumitru Untila1,2, Nicolae Spalatu3, Iuliana Caraman4, Ion Tiginyanu2,5, Mihail Caraman1
Affiliations : 1 Faculty of Physics and Engineering, Moldova State University, Alexei Mateevici, 60, MD-2009, Chisinau, Republic of Moldova; 2 Ghitu Institute of Electronic Engineering and Nanotechnologies, Academy of Sciences of Moldova, Academiei, 3/3, MD-2028, Chisinau, Republic of Moldova; 3 Tallinn University of Technology, Department of Materials Science, Ehitajate tee, 5, EE-19086 Tallinn, Estonia; 4 Engineering Department, ?Vasile Alecsandri? University of Bacau, Calea Marasesti, 157, RO-600115, Bacau, Romania; 5 Department of Microelectronics and Biomedical Engineering, Technical University of Moldova, Stefan cel Mare Avenue, 168, MD-2004, Chisinau, Republic of Moldova

Resume : The GaS compound is a layered semiconductor with the indirect band gap of ~2.6 eV. The direct and indirect band gaps are separated by ~0.45 eV energy range. GaS single crystals consist of elementary packings (S-Ga-Ga-S) linked by weak polarization forces. Bonds of ionic-covalent nature act between atoms within the packings. The specific crystal structure allows the obtaining of parallel lamella with nanometric thicknesses, by single crystals cleavage. The Ga2O3 nanometric layers were obtained onto GaS lamella surface, perpendicular to the C6 crystallographic axis, by thermal annealing (TA) in atmosphere. The structure, morphology and optical properties were studied by XRD method, AFM microscopy, Raman and absorption spectroscopies, and also light scattering spectroscopy in the fundamental absorption edge region of both ?-GaS and Ga2O3 compounds. XRD patterns contain two types of lines: intense, with narrow contour, assigned to the (002) and (004) planes of ?-GaS crystal, and low intensity lines, with wide contour, characteristic for the (002), (111) and (311) planes of Ga2O3 oxide. There, also, the lines from the (110) and (300) atomic planes of Ga2S3 crystals are slightly highlighted. Thus, on the basis of the XRD analysis, it can be admitted that as a result of the GaS lamella TA in atmosphere, a composite consisting of GaS lamellae, Ga2O3 nanolamella, and traces of Ga2S3, is formed. The formation of Ga2O3 phase is also confirmed by Raman spectroscopy.

Authors : Yaroslav S. Kochergin,[1] Dana Schwarz,[1] Arun Ichangi,[2] Michael J. Bojdys*,[1,2].
Affiliations : [1] Charles University, Faculty of Science, Department of Organic Chemistry, Hlavova 8, Prague 2, Czech Republic, 128 43. [2] Institute of Organic Chemistry and Biochemistry of the CAS, Flemingovo nám. 2, Prague 6, Czech Republic, 166 10.

Resume : Purely organic conjugated microporous polymers (CMPs) are gaining an importance as materials for organic electronics, energy storage and photocatalysis. Accordingly, we have previously developed band-gap-tuneable donor?acceptor (D-A) sulfur- and nitrogen-containing polymers (SNPs) as a subclass of CMPs via Sonogashira?Hagihara cross-coupling. Due to open pore structure these materials can be easily modified by post-synthetic p-doping with iodine, and show good results in photocatalytic water splitting. Here, we used Pd-catalysed Stilled coupling to synthesise eight new materials to increase our knowledge about D-A polymers and expand the library of SNPs. As for electron-donor motifs we used four thiophene-based linkers: thienothiophene, dithiophene, benzotrithiophene, and naphthodithiophene. From the other hand, triazine ring, a key building block of covalent triazine-based frameworks, is known to be a good electron-acceptor. Commercially available cyanuric chloride and easy-to-synthesise tris-bromophenyltriazine were used as a source of triazine core. All materials are highly fluorescent and have mixed micro-/mesoporous structure with Brunauer?Emmet?Teller specific surface area and CO2 uptake up to 656 m2g-1 and 2,04 mmolg-1 respectively. The combination of ?-conjugated structure as well as D-A nature allows the control over the optical band-gap in the resulting materials (from 2.28 eV to 2.60 eV). Moreover, prepared SNPs can be used as fluorescence-on and fluorescence-off sensors for organic volatile compounds detecting. References. D. Schwarz, Y. S. Kochergin, A. Acharjya, A. Ichangi, M. V. Opanasenko, J. ?ejka, U. Lappan, P. Arki, J. He, J. Schmidt, P. Nachtigall, A. Thomas, J. Tarábek and M. J. Bojdys, Chem. - Eur. J., 2017, 23, 13023-13027.

Authors : Rahul Bhattacharyya, Shobit Omar
Affiliations : Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, Uttar Pradesh, India 208016

Resume : Sodium bismuth titanate (NBT) recently has drawn immense research interest as a fast oxygen-ion conductor because of its high oxide-ion conductivity comparable with the other state-of-art materials like Gd0.10Ce0.90O2-?. Non-stoichiometric NBT compositions with Na/Bi molar ratio >1 exhibit at least three orders of higher conductivity than that of compositions having this ratio less than unity. In our recent work, we have shown that replacing Na for A-site Bi can lead to a significant conductivity enhancement. The present work aims to investigate the phase stability and conductivity behaviour on doping divalent and trivalent cations at the B-site in Na0.54Bi0.46TiO3-?. The conventional solid oxide route was used to fabricate the dense polycrystalline samples of Na0.54Bi0.46T1-xMxO3-? (M = Mg2 and Ga3 ). XRD indicated the presence of distorted perovskite rhombohedral structure in all the samples. SEM revealed the presence of secondary phases of Na2Ti6O13 and other compounds. Impedance spectroscopy showed improvement in grain conductivity on Mg2 doping in Na0.54Bi0.46TiO3-?, while Ga3 substitution leads to a monotonous lowering of conductivity. Among the tested compositions, the maximum grain conductivity of ~14 was observed at 600oC in air. The conductivity results and the ageing behaviour of Na0.54Bi0.46T1-xMxO3- ? at 600oC in air and reducing conditions will be presented.

Authors : Federico Baiutti,* Giuliano Gregori, Y. Eren Suyolcu, Yi Wang, Georg Cristiani, Wilfried Sigle, Peter A. van Aken, Gennady Logvenov, and Joachim Maier
Affiliations : Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany.

Resume : Oxide epitaxial heterointerfaces possess a number of fascinating properties, spanning from superior electrical conductivity to magnetism, which do not belong to the constituting phases and which result from the interplay between different local phenomena. In this contribution, we present a study on the fascinating properties arising at the contact between lanthanum cuprate (La2CuO4) and Sr-doped lanthanum nickelate (La2-xSrxNiO4), which have been investigated in MBE-grown bilayers and superlattice systems. We show that high-temperature superconductivity arises in La2CuO4 within a nm-region at the interface (with superconducting critical temperature Tc up to 40 K) and that such a property can be tuned as a function of the supercell structural parameters, i.e. doping level in the nickelate, supercell thickness and layers sequencing. By employing a number of complementary techniques, including electrical conductivity measurement, aberration-corrected scanning transmission electron microscopy and spectroscopy, we were able to correlate the system functionalities with the local interface chemistry. This allowed us to propose a mechanism for local high-temperature superconductivity in the light of a generalized space-charge theory for oxide systems, which accounts of both ionic and electronic redistribution effects.

Authors : Alexey Markov, Aleksandr Ushakov, Mikhail Patrakeev, Ilya Leonidov, Victor Kozhevnikov
Affiliations : Institute of Solid State Chemistry, Ural Branch of RAS, Pervomayskay str. 91, 620990 Yekaterinburg, Russia

Resume : The perovskite-like oxide SrFe0.8Mo0.2O3-? is shown to combine valuable characteristics allowed utilizing it for the development of novel oxygen permeable membrane materials. The serious drawback of this material is related to poor sintering at ceramic processing. It is well known that partial substitution of Sr by La is beneficial for improved sinterability and densification of the ferrous ceramics. This work was focused on studying of lanthanum concentration influence on ceramic and transport properties of Sr1-xLaxFe0.8Mo0.2O3-?. Complex oxides Sr1-xLaxFe0.8Mo0.2O3-?, where x=0.05, 0.1 and 0.2, were prepared by glycine-nitrate synthesis. X-ray powder diffraction of Sr1-xLaxFe0.8Mo0.2O3-? show formation of single phase samples with cubic structure (s.g. Pm3-m). According to the thermal properties measurements in air, partial substitution of strontium by lanthanum results in a decrease of oxygen content variations at heating and respective improvement of thermomechanical properties. Analysis of electrical conductivity measurements carried out in the oxygen pressure range of 10-18-0.3 atm at temperatures 750-950ºC reveals increase of n-type electron conductivity in response to increasing lanthanum concentration in Sr1-xLaxFe0.8Mo0.2O3-?. Gas-tight tubular membranes were successfully fabricated from Sr0.8La0.2Fe0.8Mo0.2O3-?. This work was supported by the RFBR (grant 17-08-01029).

Authors : N. Korsunska1, Yu. Polishchuk1, M. Baran1, V. Nosenko1, I. Vorona1, S. Lavoryk1,2, S. Ponomaryov1, O. Marie3, X. Portier4, L. Khomenkova1,5
Affiliations : 1) V. Lashkaryov Institute of Semiconductor Physics of the National Academy of Sciences of Ukraine, 45 Pr. Nauky, 03028 Kyiv, Ukraine; 2) NanoMedTech LLC, 68 Antonovycha Str, Kyiv 03680, Ukraine; 3) LCS (UMR CNRS 6506/ENSICAEN/Normandie Université), 6 Boulevard Maréchal Juin, 14050 Caen, France; 4) CIMAP (CEA/UMR CNRS 6252/ENSICAEN/Normandie Université), 6 Boulevard Maréchal Juin, 14050 Caen, France; 5) National University ?Kyiv-Mohyla Academy?, 2 Skovorody str., Kyiv 04070, Ukraine

Resume : Zirconia nanopowders doped with subvalent ions have attracted considerable attention due to their mechanical, electrical, thermal and luminescent properties offering diverse applications such as catalysts, solid oxide fuel cells, high temperature resistant coatings, biological labeling, etc. In the most cases, to prepare zirconia-based powders, zirconium oxychloride is used. In the present paper we will demonstrate the effect of chlorine on spatial distribution of subvalent dopants and oxygen vacancies? content in Cu-doped Y-stabilized ZrO2 nanopowders prepared by co-precipitation technique. This effect was studied versus calcination temperature and Cu content. Zirconium oxychloride was used as Zr-based precursor. Optical and structural properties of the powders were studied using diffuse and attenuated total reflectances as well as XRD, EPR and Auger spectroscopy methods. It was observed that the increase of calcination temperature stimulates structure transformation, variation of oxygen vacancies content in the grains and amount of dispersed CuO at their surface. These changes depend on Cu content being controlled by surface-volume copper redistribution (copper in- and out-diffusion) and transformation of surface entities. At low Cu content, the amount of oxygen vacancies and CuO varies significantly and non-monotonically with temperature rise, while for higher Cu content, they changes slightly. The presence of chlorine inside ZrO2 grains was detected. This allowed assuming that slow formation of oxygen vacancies is due to Cl action as compensator for Cu charge. Besides, tight Cu-Cl interaction keeps Cu ions inside the grains that affects significantly the formation of CuO at their surface. The latter reduces the catalytic activity of the powders in the CO PROX reaction.

Authors : Xiaorui Tong, William Bowman, Peter A. Crozier and David S. Mebane
Affiliations : Mechanical and Aerospace Engineering, West Virginia University

Resume : In doped systems of electroceramics, the presence of grain boundaries leads to defect redistributions, resulting in important material property changes. Conventional space charge theories have been established to model compositional changes near grain boundaries, based on the assumption of dilute dopant level. The fact that concentrated doped systems are widely employed in solid oxide fuel cells and other applications, demands a novel methodology that could be applied for these systems, where the premise of conventional models couldn’t be satisfied. Based on a thermodynamic framework of the Poisson-Cahn theory, a unified methodology has been developed to treat doped systems of all concentrations, expanding from the simplest case without defect interactions and gradient contributions to the more complicated cases where both effects become significant. The functional forms of defect interactions and gradient energy contributions are built through Bayesian calibration with discrepancy functions using EELS data of CaO doped ceria.

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Interface & Surface Phenomena (IV) : David Diercks and Werner Sitte
Authors : Yan Chen
Affiliations : Guangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Institute, School of Environment and Energy, South China University of Technology, Guangzhou510006, China.

Resume : Perovskite-based materials have been widely studied as the electrode materials for high temperature electrochemical systems such as solid oxide fuel cells and solid state electrolysis cells, and other low-temperature electrochemical devices such as alkaline membrane fuel cells and metal?air batteries. While many perovskite-based electrodes have shown remarkable performance, cation segregation near the surface or interfaces is often observed, which greatly impacts not only electrode kinetics but also their durability and operational lifespan. The segregation of A-site alkaline earth metal oxides was reported to degrade the electrochemical performance in literature. In contrast, the segregation or exsolution of B-site transition metals and the formation of metal/oxide interface were found to significantly enhance catalyst activities and stability for the electrodes. Despite of many corresponding examples, contradicting results were reported in literature. A detail understanding of the correlation between the surface cation composition and the electrochemical reaction kinetics near the surface and interface is vital to achieving the rational design of more efficient perovskite based electrode materials with excellent durability. In this study, we aimed to provide critical insights into the mechanisms of cation segregation and provide the guide line for how to enhance desired positive effects while suppressing negative effects associated with cation segregation under operating conditions. (La,Sr)MO3 (M is the transition metal) thin films grown by pulsed laser deposition were used as model systems. The evolution of surface cation composition, morphology and local electronic structure as a function of temperature, gas environment and electric potential were systematic investigated. We observed the segregation of Sr on the surface of (La,Sr)(Fe,Co)O3 (LSCF) thin films after long time operation in oxygen environment at high temperature (500 to 600o C), which lead to the degradation of oxygen reduction reaction (ORR) activity. After the deposition of PrxCe1-xOy (PCO, x=0, 0.2, 1) surface modification layer, both the ORR activity and stability of LSCF were greatly enhanced. Based on SEM, XPS and TEM measurements, we believe such enhancement is partly due to the suppression of A-site metal Sr segregation on LSCF surface by the top PCO layer at elevated temperature. Furthermore, the surface modification was found to change the rate limiting step of ORR on the surface, which was attributed to the change of surface electronic structure as quantified by in-situ scanning tunneling microscopy/spectroscopy. By annealing in reducing condition or applying an cathodic potential, the exsolution of B site cation was observed on the surface of (La,Sr)MO3 (M=Ni,Fe,Ti) oxide. The local electronic structure changes introduced by B site exsolution were studied in details and were correlated to the catalytic activity enhancement.

Authors : Tatsumi Ishihara (a,b), Lin Liu(a), Kaveh Edalati (b), Zenji Horita(b,c)
Affiliations : a)Department of Applied Chemustry, Faculty of Engineering, Kyushu University;b)International Institute for Carbon Neutral energy Research, Kyushu University; c)Department of Materials, Faculty of Engineering, Kyushu University,

Resume : Formation of NO which is toxic to human body and environment, is mainly occurred from combustion engines and so, removal of NO from exhaust gas is highly important issue at present. There are several methods reported for NO removal and among them, NO direct decomposition is the most ideal reaction because no reductant is required. In spite of spontaneous reaction, the active catalyst for NO decomposition is limited and low activity because of the deactivation of catalyst by the formed oxygen. In our previous study, we found that Ba doped Y2O3 shows high activity to NO decomposition, however, high reaction temperature is essentially required. In this study, effects of oxygen vacancy introduced into Er doped Y2O3 lattice by high pressure torsion treatment on NO decomposition activity were investigated. The high pressure torsion (HPT) is an effective technique for stabilizing high-pressure phases at ambient pressure and introducing oxygen vacancy effectively. Starting material was Y2O3 powder with 1 mol% Eu2O3. The HPT treatment was performed at room temperature by using around 0.2 g powder and applied at upper anvil for 1 turns. Plastic strain was introduced at 3 or 6 GP. Pulsed reaction was used for NO decomposition activity coupled with an online gas analyser. NO (1% in He) was subsequently introduced into the reactor to assess NO adsorption and decomposition. An online mass spectrometric detector was used to monitor the signals at m/z values of 28 (N2), 30 (NO), 32 (O2) and 44 (N2O). Although N2 formation was observed at initial few pulses on Er doped Y2O3 without HPT, NO decomposition was significantly deactivated. On the other hand, N2 and N2O yield was much increased by application of HPT treatment which could introduce oxygen vacancy and grain boundary, and N2 formation was stably observed over few 10 NO pulses. Therefore, oxygen vacancy might be work as active site for NO decomposition and increase in oxygen vacancy. Among the samples at different HTP treatment, Y2O3 by HTP at 3GPa shows the highest NO decomposition activity. However, O2 desorption was not observed and this could be explained that only increase in oxygen vacancy is not enough for increasing NO decomposition activity but also diffusivity in oxygen vacancy is essential for increasing NO decomposition activity in low temperature range. Effects of oxygen vacancy on NO adsorption state will be discussed in details based on FT-IR measurement.

Authors : Peter A. van Aken, Y. Eren Suyolcu, Yi Wang, Federico Baiutti, Giuliano Gregori, Georg Cristiani, Wilfried Sigle, Joachim Maier, Gennady Logvenov
Affiliations : Max Planck Institute for Solid State Research, Stuttgart, Germany

Resume : Epitaxial interfaces in oxides have been extensively studied recently. One of the most intriguing interface effects is high-temperature interfacial superconductivity (HT-IS). In this study, La2CuO4-based bilayers were grown by oxide molecular beam epitaxy. They consist of a metallic (M) and an insulating (I) phase. The bilayers exhibit HT-IS up to ?40 K. To assess the role of dopant size on chemistry and superconductivity at the interfaces, different dopants (Ca, Sr, and Ba) were employed in the M-phase, and the M-I bilayers were investigated by complementary techniques, including analytical scanning transmission electron microscopy (STEM). Structural quality and perfect coherent interfaces were revealed via high-angle annular dark-field STEM imaging. The dopant distribution was studied via electron energy-loss spectroscopy and dopants were found to be inhomogeneously distributed in the M layer revealing distinct differences among the three dopant species. Annular bright-field STEM imaging provided quantitative information on octahedral distortions and yielded different Jahn-Teller (JT) and anti-JT effects. A series of exciting findings are highlighted: (i) the c-lattice parameter of the bilayers is linearly dependent on the ionic size, while dopant-specific redistribution is found at the interfaces, (ii) superconductivity is highly dependent on the dopant, and (iii) the dopant distribution has a remarkable effect on the JT and anti-JT distortions.

Authors : M. Leprich, J. Hofer, W. Preis
Affiliations : Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben, Austria

Resume : Numerous electroceramic devices, such as MLCCs (multilayer ceramic capacitors) or PTCR thermistors (positive temperature coefficient of resistivity), are based on barium titanate. The PTC effect (steep increase of resistivity above the Curie point) is associated with highly conductive grains and blocking grain boundaries. Usually, this behaviour is found in the case of small dopant concentrations and fairly large grain sizes around 3 ? 5 µm, if the ceramics are sintered in air. The electrical properties of donor and acceptor co-doped BaTiO3 ceramics have been investigated as a function of oxygen partial pressure and temperature (from room temperature to 900°C) by application of impedance spectroscopy. While samples doped with 0.25% La and 0.05% Mn or commercial specimens (doped with 0.5% Y and 0.1% Mn) show the PTC effect, samples containing fairly large amounts of donors and acceptors, e.g. 2.1% La and 1.0% Mn, are highly resistive at room temperature with Arrhenius-type temperature dependence of the bulk conductivity. In addition, BaTiO3 (doped with 0.25% La and 0.05% Mn) with grain sizes in the sub-micron range (200 ? 300 nm) is highly resistive with Arrhenius-type temperature dependence, most probably because of low calcination and sintering temperatures in order to avoid grain growth. The experimental results are interpreted in terms of defect chemical models for the bulk emphasizing ionic and electronic compensation mechanisms as well as the trapping effect of Mn.

Authors : Maximilian Felix Hoedl a), Rotraut Merkle a), Evgeniy Makagon b), Igor Lubomirsky b), Eugene Kotomin a), Joachim Maier a)
Affiliations : a) Max Planck Institute for Solid State Research, Stuttgart, Germany; b) Weizmann Institute of Science, Rehovot, Israel

Resume : Yttrium doped BaZrO3 combines a high bulk proton conductivity with good chemical stability [1]. Acceptor doping, e.g. by Y3+, Sc3+, leads to oxygen vacancy formation, which allows for dissociative water incorporation. Recently, dry and hydrated BaZrO3:Y was investigated regarding its unusual electromechanical properties. Due to the cubic symmetry of the material, piezoelectricity is absent but electrostriction (the second order quadratic effect linking strain and electric field squared) could still be observed, and was found to be exceptionally high [2]. In this presentation, DFT calculations of elastic and dielectric properties of Y:BaZrO3 and Sc:BaZrO3 are discussed. The obtained Young?s moduli in dry and hydrated state are in good agreement with experimental data. Their dependencies on dopant type and concentration are decomposed into contributions from modified lattice constant and modification of the lattice by defects (acceptors, oxygen vacancies, protonic defects). Finally, a mechanism is discussed in which the response of point defect clusters to an external electric field causes a macroscopic strain that could, in principle, explain the observed high electrostriction coefficient. Funding by GIF (grant no. I-76-302.1-2015) is acknowledged. [1] K. D. Kreuer, Annu. Rev. Mater. Res. 33, 333-59 (2003) [2] N. Yavo, O. Yeheskel, E. Wachtel, A. Frenkel and I. Lubomirsky, abstract for Solid State Ionics Conference, Padua, Italy (2017)

Defects & Transport Phenomena (II) : Yan Chen and Pjotrs Zguns
Authors : C-Y. S. Chang (a), S. Khodorov (b), S. Kim (a), I. Lubomirsky (b)
Affiliations : (a) Dept. of Chemical Engineering and Materials Science, University of California, Davis, USA; (b) Dept. of Materials Science, Weizmann Institute of Science, Rehovot, Israel

Resume : Recently we have demonstrated that I?V characteristics of grain boundaries in prominent solid oxygen or proton conductors can be accurately described using a simple linear diffusion formalism (I-V model).[1-3] The model assumes that: (1) the grain boundaries do not represent physical blocking layers and (2) the ions follow Boltzmann distribution. Despite its simplicity, the model successfully reproduces the ??power law??: current proportional to voltage power Igb~(Ugb)^n. The model also correctly predicts that the product n·T, where T is the temperature in K, is constant and is proportional to the grain boundary potential, ?gb. Previously, the value of ?gb has been determined exclusively by the ratio of an effective resistivity of a single grain boundary to that of grain interior (RR model[4]). This approach assumes that the grain boundary resistance arises solely from the depletion of charge carriers in the space charge zone. However, it may have various sources causing the RR model to overestimate the value of ?gb. We demonstrate that using the I-V model, ?gb can be determined accurately even if multiple factors are responsible for the resistance. Funding by US-Israel BSF (grant no. 2016006) is acknowledged. [1] S. K. Kim, et al., Phys Chem Chem Phys 2013, 15, 8716 [2] S. K. Kim, et al., Phys Chem Chem Phys 2014, 16, 14961 [3] S. Kim, et al., Phys Chem Chem Phys 2016, 18, 3023 [4] J. Fleig, et al., J. Appl. Phys. 2000, 87, 2372

Authors : Stevin S. Pramana,1* Tom Baikie,2 Ji Wu,3 Andrew P. Horsfield,4 Stephen J. Skinner4
Affiliations : 1School of Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom 2Energy Research Institute at Nanyang Technological University, Singapore 3International Institute for Carbon-Neutral Energy Research, Kyushu University 4Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom

Resume : Oxygen hyper-stoichiometric CeNbO4+d fergusonite is reported to possess high ionic conductivity at intermediate temperatures, making it a new class of ionic conductor for energy generation and storage purposes. This provides an alternative to more commonly used perovskite and fluorite electrolytes that heavily depend on vacancy migration. In order to explore the oxygen migration dynamics in fergusonite, defect crystallography needs to be understood. We successfully grew a single crystal of CeNbO4.25 using a floating zone mirror furnace and modelled the long-range average structure by analysing the single crystal X-ray diffraction pattern, neutron and synchrotron X-ray powder diffraction data, and electron diffraction. In addition to better capture the short-range coordination environment especially around the interstitial defect sites, pair distribution function (PDF) analysis of neutron powder diffraction data was performed. The combined diffraction results show that the structure has to accommodate the interstitials by modulating the oxygen positions commensurately, creating a ~12 times larger cell with cell vectors given by the following matrix: (ar, br, cr) = (2, 0, 2 | 0, 2, 0 | -2, 0, 1) (ap, bp, cp); where the (a,b,c)r and (a,b,c)p are the resultant supercell and stoichiometric (d = 0) cell lattice vectors, respectively. The ordering of Ce3+ and Ce4+ was discovered with a continuous helical network of Ce4+Ox running parallel to the crystallographic z- axis. In addition, the coordination number of Nb expands from 6 to 7 or 8.1 To validate the experimental findings, the oxygen migration was simulated using molecular dynamics approach based on the determined superlattice. CeNbO4.25 shows significantly greater mean square displacements of oxygen at 1073K than does CeNbO4; this indicates that the interstitial oxygen ions are mobile. At higher temperature (1573 K and above), the major migration pathway lies within the NbOx polyhedra slab (xz plane), but with some connectivity along the y crystallographic axis being observed, consistent with the existence of NbO7 and NbO8. The calculated activation energies for oxygen diffusion (~1 eV) are comparable to those measured by Packer and Skinner.2 1S. S. Pramana, T. Baikie, T. An, M. G. Tucker, J. Wu, M. K. Schreyer, F. Wei, R. D. Bayliss, C. L. Kloc, T. J. White, A. P. Horsfield, S. J. Skinner. J. Am. Chem. Soc., 2016, 138, 1273-1279. 2R. J. Packer and S. J. Skinner, Adv. Mater., 2010, 22, 1613-1616.

Authors : Fabian M. Draber, Manfred Martin
Affiliations : Institute of Physical Chemistry, RWTH Aachen University, 52074 Aachen, Germany; Institute of Physical Chemistry, RWTH Aachen University, 52074 Aachen, Germany

Resume : Acceptor doped BaZrO3 is well known for its high thermodynamic stability as well as high proton conductivity. It is therefore a promising candidate for applications in solid oxide fuel cells. In the last years it has been extensively studied with experimental and theoretical methods. These studies suffer from one problem, the obtained migration energies do not fit each other. In our work we present a new approach for the calculation of the ion conductivity. Starting from density functional theory (DFT) calculations we developed a conductivity model based on pair interactions with only a few parameters, which allows us to obtain ion conductivities and activation energies by using Kinetic Monte Carlo (KMC) methods. Every introduced parameter has been thoroughly analysed to gain knowledge on its influence on the ion conductivity. Using this model we investigate proton and oxygen vacancy conductivity in BaZrO3 including the investigation of different dopants and the role of percolation pathways. Our data are compared with theoretical and experimental values from literature and we are able to reproduce several trends. Through our model studies, we are able to get deeper insight into these phenomena.

Authors : Sebastian Steiner1, Leonie Koch1, Kai-Christian Meyer1, In-Tae Seo1, Karsten Albe1 and Till Frömling1
Affiliations : 1Institute of Geo- and Materials Science, Technische Universität Darmstadt, Germany

Resume : As recently reported by Ming Li et al., A-site non-stoichiometry as well as B-site acceptor doping of Na0.5Bi0.5TiO3 (NBT) show a significant impact on the oxygen vacancy concentration and further the oxygen ionic conductivity [1, 2]. Mg acceptor doped NBT, for instance, shows an extremely high ionic conductivity comparable with conventionally used solid ion conductor materials. With respect to the experience with other lead based or lead free ferroelectric ceramics, this behavior was a rather unexpected result. The origin and defect chemical reasons for these findings are part of important ongoing research approaches. In this work, we will discuss the formation as well as the effect of oxygen vacancies in B-site acceptor doped Na0.5Bi0.5TiO3. With the help of temperature dependent impedance spectroscopy (IS) the defect chemistry and the charge carrier migration process is investigated. Furthermore, phase and charge carrier dependent simulations are included to get a deeper understanding of the origin for this unexpected conductivity behavior [3]. Based on these results we are able to propose how the investigated changes in NBT may affect other NBT related materials. References [1]. M. Li, M. J. Pietrowski, R. A. De Souza, H. Zhang, I. M. Reaney, S. N. Cook, J. A. Kilner, and D. C. Sinclair, Nat. Mater, 13, pp 31-35 (2014) [2] M. Li, H. Zhang, N. S. Cook, L. Li, J. A. Kilner, I. M Reaney, and D. C. Sinclair, Chem. Mater., 27, pp 629-634, (2015) [3] L. Koch, S. Steiner, K.-C. Meyer, I.-T. Seo, K. Albe, T. Frömling, J. Mater. Chem. C, 5, 8958-8965 (2017)

Authors : S. Wachowski, P. Winiarz, B. Kamecki, K. Dzierzgowski, A. Mielewczyk-Gry?, P. Jasi?ski, M. Gazda
Affiliations : Gda?sk University of Technology, Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Narutowicza 11/12, 80-233 Gda?sk, Poland; Gda?sk University of Technology, Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Narutowicza 11/12, 80-233 Gda?sk, Poland;Gda?sk University of Technology, Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Narutowicza 11/12, 80-233 Gda?sk, Poland;Gda?sk University of Technology, Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Narutowicza 11/12, 80-233 Gda?sk, Poland;Gda?sk University of Technology, Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Narutowicza 11/12, 80-233 Gda?sk, Poland; Gda?sk University of Technology, Faculty of Electronics, Telecommunications and Informatics, Department of Biomedical Engineering, Narutowicza 11/12, 80-233 Gda?sk, Poland; Gda?sk University of Technology, Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Narutowicza 11/12, 80-233 Gda?sk, Poland;

Resume : Acceptor doped ReBO4 (where Re is a rare earth element and B is Nb, Ta, As or Sb) are a group of chemically stable solid state proton conductors combining considerable proton conductivity, reaching 10-3 S/cm at 900 °C under wet conditions. Lanthanum niobate, the member of the group with highest ionic conductivity, undergoes a second order phase transition from tetragonal to monoclinic structure at about 500 °C, which is accompanied by an increase in the activation energy of the conductivity and a nearly twofold change of the thermal expansion coefficient (TEC). This challenge can be tackled by substituting Nb by different isovalent elements, such as As, Sb, Ta, and V to alter the phase transition temperature. This work summarizes the studies of the structure and electrical properties of solid solutions of LaNbO4-LaAsO4, LaNbO4-LaTaO4 and LaNbO4-LaSbO4. The structure of the samples has been determined by X-ray Diffraction method supported by Rietveld analysis. The electrical conductivity has been measured by Electrochemical Impedance Spectroscopy. Conductivity has been measured as a function of temperature, oxygen and water vapour partial pressure for the separation of the influence of different charge species on the total conductivity. The diffusion coefficient of oxygen ions has been determined by the isotope exchange method combined with Secondary Ion Mass Spectroscopy. This work was financially supported by the National Science Center, Poland Grant No. 2015/17/N/ST5/02813.

Authors : I. Garbayo (1), F. Chiabrera (1), N. Alayo (1), A. Morata (1), A. Tarancón (1) (2)
Affiliations : (1) Department of Advanced Materials for Energy, Catalonia Institute for Energy Research (IREC), Jardí de les Dones de Negre 1, Planta 2, 08930 Sant Adrià de Besòs (Barcelona), Spain; (2) Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís Companys 23, 08010, Barcelona, Spain

Resume : Last advances in the development of micro Solid Oxide Fuel Cells (?SOFC) have been connected with the downscaling of traditional SOFC functional layers to thin films, together with their integration in silicon technology. Classical restrictions of SOFC could be overcome, being able to lower the operating temperature to 400ºC. Despite such important leap, the technology encountered a new dilemma, since fast degradation was still found on the utilized metallic electrodes, but further lowering down was hindered by the internal resistance of the electrolyte. Operating at lower temperatures is desired, since it would not only allow a safe and stable use of metals, but would also facilitate an easier integration in real devices. For that, electrolyte materials with superior oxide-ion conduction need to be investigated. Here, we present the optimization of Bi2V0.9Cu0.1O5.35 (BICUVOX) as a thin film electrolyte for ?SOFC. Despite its high ionic conductivity, a poor chemical stability and low compatibility with other components of the cells have traditionally impeded its utilization in classical SOFC. However, the use of thin films and in a new low temperature range could solve the problem. A complete structural and electrochemical characterization of BICUVOX films deposited by pulsed laser deposition has been carried out, aiming to stabilize the high conducting aurivillus tetragonal phase. Best performing films showed the potential use of this material at temperatures as low as 250ºC.

Authors : F. Chiabrera (1), L. López-Conesa (2), A. Chroneos (3)(4), A. Kordatos (3), I. Garbayo (1), A. Morata (1), A. Ruiz-Caridad (2), S. Estradé (2), F. Peiró (2), A. Tarancón (1)(5)
Affiliations : (1) Department of Advanced Materials for Energy, Catalonia Institute for Energy Research (IREC), Jardí de les Dones de Negre 1, Sant Adrià de Besòs, 08930 , Spain.; (2) Department of Electronics, University of Barcelona, C. de Martí i Franquès 1, 08028 Barcelona, Spain: (3) Faculty of Engineering, Environment and Computing, Coventry University, Priory Street, Coventry CV1 5FB, United Kingdom; (4) Department of Materials, Imperial College London, London SW7 2AZ, United Kingdom; (5) Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís Companys 23, 08010, Barcelona, Spain;

Resume : The large impact of grain boundaries (GB) on the electrochemical behaviour of polycrystalline oxides materials has received increasing attention in the past decades. While for a large number of oxides GBs have been demonstrated to be detrimental for oxygen mass transport properties, recent studies showed that they produces a large enhancement of oxygen diffusion in Sr-doped Lanthanum Manganite (LSM) polycrystalline thin films. To understand and control the extraordinary properties of LSM GBs, we systematically investigated their chemical and structural composition in pulsed laser deposited polycrystalline thin films by High-resolution Transmission Electron Microscope (HR-TEM) and electron energy loss spectroscopy (EELS). The analysis revealed that a high density of dislocations occurs at the interface between the different oriented grains, along with a rearrangement of cationic composition. Also, the GBs show oxygen deficiency, which, in opposition to the typical hyper-stoichiometry presents in bulk LSM, appears to be the origin of the enhanced mass transport properties. We performed Density Functional Theory (DFT) calculations to investigate the formation energy of the cationic defects found in the GBs. The analysis revealed a strong intercorrelation among the various defects, helping to explain the local defect chemistry found by TEM. Finally, we analyzed the impact of the GBs local composition on electronic conduction, confronting polycrystalline and epitaxial thin films.

Solid State Electronic Devices (III): Iontronics : Susanne Hoffmann-Eifert and José Santiso
Authors : Nini Pryds, Dennis Christensen and Yunzhong Chen
Affiliations : Department for Energy Conversion and Storage, Technical University of Denmark, DK-4000 Roskilde, Denmark

Resume : Understanding how the carrier mobility can be increased in oxides is one of the most significant challenges in order to obtain nanoelectronic based devices. The mobility of complex oxide is still orders of magnitude lower than that of semiconductors and with the current fabrication method we are still not fully able to control the carrier mobility at the interface. Here I will provide an overview of interface defects which influence the mobility at the interface observed in SrTiO3 (STO)-based heterostructures. I will also show that different scattering mechanisms at the 2D electron gas (2DEG) of SrTiO3-based interfaces can be controlled by defect engineering leading to enhanced mobility. Based on the enhanced mobility, in 2DEG samples of unprecedented structural perfection, we have recently studied the Quantum Hall Effect (QHE) which reveal the strength of enhancing the mobility. I will also show some results observed at these interfaces indicating a large positive magnetoresistance of 80,000% and the presence of a highly strain-tunable magnetic order. This collection of samples offers unique opportunities for a wide range of rich world of mesoscopic physics and future nanoelectronics.

Authors : Yongsuk Choi, Hyunwoo Kim, Jeehye Yang, Min Je Kim, Ajjiporn Dathbun, Dong Un Lim, Seung Won Shin, Soong Ho Um, Sungjoo Lee, Moon Sung Kang,* and Jeong Ho Cho*
Affiliations : Yongsuk Choi, Hyunwoo Kim, Min Je Kim, Ajjiporn Dathbun, Dong Un Lim, Prof. Soong Ho Um, Prof. Sungjoo Lee, Prof. Jeong Ho Cho SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea. Jeehye Yang, Prof. Moon Sung Kang Department of Chemical Engineering, Soongsil University, Seoul 156-743, Republic of Korea. Seung Won Shin, Prof. Soong Ho Um School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea.

Resume : Room temperature electron mobility of >130 cm2V-1s-1 is achieved for a few-layer MoS2 transistor by use of a polyanionic proton conductor as the top-gate dielectric of the device. The use of a proton conductor that inherently exhibits a cationic transport number close to 1 yields unipolar electron transport in the MoS2 channel. The high mobility value is attributed to the effective formation of an electric double layer by the proton conductor, which facilitates electron injection into the MoS2 channel, and to the effective screening of the charged impurities in the vicinity of the device channel. Through careful temperature-dependent transistor and capacitor measurements, we also confirm quenching of the phonon modes in the proton-conductor-gated MoS2 channel, which should also contribute to the achieved high mobility. These devices are then used to assemble a simple resistive-load inverter logic circuit, which can be switched at high frequencies above 1 kHz.

Authors : Ajjiporn Dathbun,? Youngchan Kim,? Seongchan Kim,? Min Je Kim,? Yongsuk Choi,? Dong Un Lim,? Youngjae Yoo,? Moon Sung Kang,? Changgu Lee,*,?,? and Jeong Ho Cho
Affiliations : ?SKKU Advanced Institute of Nanotechnology (SAINT), ?School of Mechanical Engineering, §School of Chemical Engineering, Sungkyunkwan University, Suwon 440?746, Korea ?Division of Advanced Materials, Korea Research Institute of Chemical Technology, Daejeon 305-600, Korea ?Department of Chemical Engineering, Soongsil University, Seoul 156-743, Korea

Resume : We demonstrated the fabrication of large-area ReS2 transistors and logic gates composed of a chemical vapor deposition (CVD)-grown multilayer ReS2 semiconductor channel and graphene electrodes. Single-layer graphene was used as the source/drain and coplanar gate electrodes. An ion gel with an ultrahigh capacitance e?ectively gated the ReS2 channel at a low voltage, below 2 V, through a coplanar gate. The contact resistance of the ion gel-gated ReS2 transistors with graphene electrodes decreased dramatically compared with the SiO2-devices prepared with Cr electrodes. The resulting transistors exhibited good device performances, including a maximum electron mobility of 0.9 cm2/(V s) and an on/o? current ratio exceeding 104. NMOS logic devices, such as NOT, NAND, and NOR gates, were assembled using the resulting transistors as a proof of concept demonstration of the applicability of the devices to complex logic circuits. The large-area synthesis of ReS2 semiconductors and graphene electrodes and their applications in logic devices open up new opportunities for realizing future ?exible electronics based on 2D nanomaterials.

Authors : T.V. Perevalov(1,2), A.A. Gismatulin(1), V.F. Voronkovsky(1), V.A. Gritsenko(1,2,3), A.K. Gerasimova(1), V.Sh. Aliev(1), I.A. Prosvirin(4)
Affiliations : (1) Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave, 630090, Novosibirsk, Russia; (2) Novosibirsk National Research University, 2 Pirogova Str., 630090 Novosibirsk, Russia; (3) Novosibirsk State Technical University, 20 K. Marksa ave,, 630073, Novosibirsk, Russia; (4) Ural State Technical University, 19 Mira Str., 620002 Ekaterinburg, Russia

Resume : Stoichiometric tantalum oxide (Ta2O5) dielectric films find wide applications in microelectronics due to their high dielectric constant, electrical strength and good thermal and chemical stability. For the last years, the interest in tantalum oxide has strongly increased due to its successful use in nonvolatile resistive random-access memories (ReRAM) or/and memristors. The optical and transport properties of non-stoichiometric tantalum oxide thin films grown by ion beam sputtering were investigated in order to understand the dominant charge transport mechanisms and reveal the traps nature. The TaOx films content was analyzed by X-ray photoelectron spectroscopy. From the optical absorption and photoluminescence measurements, and density functional theory simulations, it was concluded that the 2.75 eV blue luminescence excited in a TaOx films by 4.45 eV photons, originates from oxygen vacancies. These vacancies are also responsible for a TaOx conductivity. The thermal trap energy of 0.85 eV determined from the transport experiments coincides with half of the blue luminescence band Stokes shift. It is argued that the dominant charge transport mechanism in TaOx films is a phonon-assisted tunneling via traps. The exponential leakage current increase in TaOx with the decreasing x is explained by the increasing oxygen vacancy corresponding to a smaller distance between traps.

Authors : P. Grey, S. N. Fernandes, D. Gaspar, I. Cunha, R. Martins, E. Fortunato, M. H. Godinho, L. Pereira
Affiliations : CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia FCT, Universidade Nova de Lisboa and CEMOP-UNINOVA, Campus da Caparica 2829-516, Caparica, Portugal

Resume : We report on the fabrication of solid-state photonic electrolytes based on cellulose nanocrystals (CNCs) and their integration into transistor devices. The CNC films with a left-handed internal long-range order are produced via evaporation induced self-assembly and consequently infiltrated with alkali ions (Li, Na and K) to yield highly polarizable chiral nematic electrolytes. The influence of anisotropy is studied through electrochemical impedance spectroscopy, yielding capacitances between 5 and 10 ?F cm-2. They are employed as gate dielectrics in electric double layer sputtered amorphous indium-gallium-zinc-oxide (a-IGZO) transistors. The obtained devices operate in depletion mode at low voltages (< 2 V), with On-Off ratios of up to 7 orders of magnitude, subthreshold swings of 77 mV dec-1 and saturation mobilities of 8.3 cm2 V-1 s-1. Anisotropic solid-state electrolytes based on abundant biopolymers show great potential for high performing cheap electronics. It is crucial to understand the fundamental transport mechanisms and their potential impact on technology, when compare to their isotropic counterparts. The developed films can find application in solid-state ionics for batteries, electrochemistry and microelectronic circuits.

Authors : E. Mishuk, E. Makagon, A.D. Ushakov, E. Wachtel, S.R. Cohen, R. Popovitz-Biro, V. Ya. Shur, A.L. Kholkin, I. Lubomirsky
Affiliations : Department of Materials and Interfaces, Weizmann Institute of Science, Israel; Department of Chemical Research Support, Weizmann Institute of Science, Israel; School of Natural Sciences and Mathematics, Ural Federal University, Russia; Department of Physics and CICECO ? Aveiro Institute of Materials, University of Aveiro, Portugal

Resume : Gadolinium-doped ceria (GDC) exhibits electrostriction that is comparable in magnitude to the field-induced strain of commercial, Pb-based electrostrictors. Given the ecological preference for ceria over Pb, we fabricated robust GDC self-supported MEMS in the form of millimeter-sized membranes, bridges, and cantilevers, using only Si-compatible processes and materials. We observed that the electrical contacts play a critical role in device functionality. Ti electrodes are the most suitable for active GDC membrane MEMS, as Ti contact resistance is lower than for Cr, Ni, Al and Ag electrodes. Measurements of membrane-displacement with atomic force microscopy and Michelson-Morley interferometry revealed a predominantly linear (1st harmonic) response to applied AC voltage (zero DC bias). We found that the amplitude of the 1st harmonic component is an exponentially increasing function of temperature with activation energy very similar to that for oxygen diffusion. Our results highlight a connection between electrostrictive strain and charge transport in GDC films. In the absence of electronic conduction, development of an electric field in the film depends on the mobility of oxygen vacancies, which renders the electro-mechanical properties more complex than in the case of classical electrostrictors. Funding by the Israeli MoS&T 3-12944 and 3-12421(collaboration with Russian Federation) and by the Russian Foundation for Basic Research (grant 15-52-06006 MNTI_?) are acknowledged.

Authors : Marina Muñoz-Castro1, Nicolai Walter2, Wolfram Pernice2, Hartmut Bracht1
Affiliations : 1University of Münster, Institute of Materials Physics, D-48149 Münster, Germany 2University of Münster, Physikalisches Institut, D-48149 Münster, Germany

Resume : Optical modulators are essential elements of photonic integrated circuits, where these devices are required for tuning, reconfiguration and stabilization operations. Different physical processes are used to manipulate the optical properties of a medium. In electrochromic materials, the optical behaviour is altered by electrochemical injection of ions and electrons. Applying an external voltage, the composition of the material changes, inducing a continuous variation of the optical properties. This mechanism could be exploited to realize an electrically driven optical modulator for photonic applications. To prove this concept we choose V2O5, a well-known cathode material for Li ion batteries [1], its layered structure can reversibly uptake/release a great amount of ions, and its optical properties are very sensitive to changes in stoichiometry. Adjusting the Li content in the V2O5 layers, the refractive index n and the extinction coefficient k shift [2]. This feature enables manipulating intensity and phase of light beams in very compact devices [3]. To implement this modulation in a photonic chip, a sputtered multi-layer stack is realized, where the ions reversibly travel from the Li-ion source to the V2O5 layer (battery principle) producing the desired change of the optical properties. [1] M. Winter et al., Adv. Mater. 10 (1998) 725. [2] M. Muñoz-Castro et al., J. Appl. Phys. 120 (2016) 135106. [3] S. Zanotto et al., Adv. Opt. Mater. 5 (2017) 1600732.

Solid State Energy Devices (IV): Fuel Cell Cathodes : Dino Klotz and Jürgen Fleig
Authors : Stephen J. Skinner, Andrea Cavallaro, Stevin Pramana, Chris Nicklin, Celeste van den Bosch
Affiliations : Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ, UK; School of Engineering, Merz Court, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK; Diamond Light Source Ltd, Diamond House, Harwell Science & Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK

Resume : Surface and interfaces in electrochemical devices are key to the effective development of durable and efficient devices. Understanding the key processes such as oxygen reduction and incorporation, cation transport and segregation in oxide based devices is particularly challenging as both structure and chemistry have to be considered. In order to clearly elucidate the contributions at solid-solid and solid-gas interfaces a combination of techniques are required, and in this work we explore the interfaces in a model electrode system using primarily X-ray crystal truncation rod measurements as a function of operating conditions, and will highlight the power of this technique in exploring buried interfaces. This will be coupled with ion beam and X-ray spectroscopy measurements to provide a full picture of the atomic scale processes governing key mass transport phenomena.

Authors : M. Acosta1, F. Baiutti2, A. Tarancón2,3, J. L. MacManus-Driscoll1
Affiliations : 1 Department of Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road 27, CB3 0FS, Cambridge, UK 2 Institut de Recerca en Energia de Catalunya (IREC), Jardins de les Dones de Negre 1, 08930, Sant Adrià de Besòs, Barcelona, Spain 3 ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain

Resume : Micro-solid oxide fuel cells (SOFC) can run with a broad variety of hydrocarbon fuels and feature low or even zero pollutant emissions, thus they can play a major role in the future portable power sources and can even act as sensors for the internet of things. Despite their potential, their applicability remains limited due to the high operating temperatures required for sufficiently high oxygen reduction and transport. In this work, we present a novel approach to develop epitaxial and mesoporous thin films with the aim to maximize the surface area of the films. Using pulsed laser deposition, we grew vertically aligned nanocomposites based on (La,Sr)(Co,Fe)O3 (LSCF) and different secondary phases. We optimize deposition parameters to obtain a two-phase composite with nanopillars between 20 nm and 100 nm. Selective etch-out of the nanopillars rendered mesoporous honeycomb-like nanostructures LSCF. It is demonstrated that by modifying the density and size of nanopillars, not only the nanostructure can be altered, but also it can be used as a strain engineering strategy to tune LSCF conductivity and catalytic activity. A thorough structural and functional characterization of the mesoporous materials will be presented to reveal synthesis-nanostructure properties. The results open a new route to develop nanostructured epitaxial mesoporous electrodes for micro-SOFC.

Authors : Yuexing Zhu, Ben Levitas, Srikanth Gopalan
Affiliations : Division of Materials Science and Engineering; Division of Materials Science and Engineering; Department of Mechanical Engineering & Division of Materials Science and Engineering

Resume : In this work, we focus on the oxygen electrode of solid oxide fuel cells where oxygen reduction occurs in two steps?adsorption and electronation, and surface/bulk diffusion to incorporation sites. Complex transition metal perovskite oxides such as strontium-doped lanthanum manganite (LSM) and strontium-doped cobalt iron oxide (LSCF) have been used as SOFC cathode materials. However both individually lack the key characteristics to successfully complete oxygen reduction. Furthermore, the accumulation of chromium (chromium poisoning) on SOFC cathodes is known to significantly hinder the performance of the cells. Incorporating core-shell hetero-structures as the cathode material could alleviate this problem: effectively combining the functionalities of both materials, and providing a nanoscale protection from Cr poisoning with a shell such as Cr-doped LSM (LSCM). However, synthesizing core-shell cathode structures previously has proved difficult requiring multiple steps, resulting in non-uniform core-shell structures. In this work, we utilize a molten salt synthesis process to synthesize core-shell structures with tailored length scales of the core and shell with great compositional control. The core is synthesized using any convenient processing method and added to a molten salt solvent. To this solvent, precursors of the shell forming materials added in calculated amounts. So long as the Gibbs free energy of formation of the target shell material from the precursors is sufficiently negative, the shell forms through a heterogeneous nucleation process around the core. The thickness and composition of the shell can be controlled by varying the process variables, namely precursor concentration in the solution, temperature, and time.

Authors : Mingi Choi, Jongseo Lee, and Wonyoung Lee
Affiliations : Sungkyunkwan University, Sungkyunkwan University, Sungkyunkwan University

Resume : The nano-structured composite electrode, with a carefully conducted infiltration process, is one of the most promising electrode structures for intermediate temperature solid oxide fuel cells (IT-SOFCs), due to its promoted oxygen reduction reaction (ORR) and enlarged triple phase boundaries (TPBs). Among the various morphologies using infiltration, we reports an effect of film-coated cathode for IT-SOFCs with enhanced ORR kinetics and excellent stability. To facilitate the wet-chemical based film-coating technique, we controlled the fluid mechanical parameters when we prepared the precursor solution and pre-heating process of as-infiltrated samples. Following those approaches, we successfully deposited the target materials on the prepared scaffolds in a thickness of ~5 nm. Through the film-coating technique, we systematically designed the nano-structured Sm0.5Sr0.5CoO3-? (SSC)/Gd0.2Ce0.8O2-? (GDC) composite cathode. The film-coated SSC/GDC composite cathode showed the ~30% reduction in polarization resistance (Rp) and ~15% increase in peak power density at 650 °C compared to the conventionally coated cathode (discrete feature) in spite of ~12-fold less loading of infiltration materials. Furthermore, the film-coated cathode showed an excellent stability, maintaining an Rp of 0.029 ?cm2 for 100 h at 650 °C. Our results demonstrated that high performance and stability of the composite cathode for IT-SOFCs can be achieved through a thin-film coated cathode.

Authors : Ja Yang Koo, Yonghyun Lim, Young Beoom Kim, Doyoung Byun, Wonyoung Lee
Affiliations : School of Mechanical Engineering, Sungkyunkwan Univeristy; Department of Mechanical Convergence Engineering, Hanyang Univeristy; Department of Mechanical Convergence Engineering, Hanyang Univeristy; School of Mechanical Engineering, Sungkyunkwan Univeristy; School of Mechanical Engineering, Sungkyunkwan Univeristy

Resume : The high operating temperature (800?1000 ºC) of solid oxide fuel cells (SOFCs) has been a critical technical hindrance for broader applications because of a low chemical stability, slow start-up, and high system cost. At reduced temperatures, especially at low temperatures (< 500 ºC), the significant increases in SOFC components, in particular the polarization resistance of cathode, become critical as they often determine the entire SOFC performance. In particular, the oxygen reduction reactions (ORRs) at the cathode usually dominate the entire ionic transfer. Therefore, a high-performance cathode is crucial for the enhancement of SOFCs at low temperatures. In this study, we report a 3.5-fold improvement in the performance of SOFCs operating at 450 ºC with functional layer between the electrolyte and cathode, composed by electrospun yttria-stabilized zirconia (YSZ) nanofibers. YSZ nanofibers with diameters of 150-200 nm were uniformly deposited on single-crystal YSZ substrate. The dramatically enhanced polarization resistances were shown in electrochemical impedance spectroscopy, and that was caused by high specific surface, high porosity and nano-crystalline structure of the YSZ nanofiber functional layers. Our results show the possibility of applying YSZ nanofibers for the enhancement of high performance low temperature SOFCs.

Authors : Reihaneh Zohourian, Rotraut Merkle, Joachim Maier
Affiliations : Max Planck Institute for Solid State Research

Resume : Mixed-conducting perovskites with VO.., h. and OHO. are potential cathode materials for protonic ceramic fuel cells (PCFC). They incorporate protons either by hydration (water uptake, acid-base reaction for ) or hydrogenation (hydrogen uptake, redox reaction for )[1]. Thermogravimetry shows that the hydration degree is smaller for (Ba,Sr,La)(Fe,Co,Zn,Y)O3-? cathode materials compared to Ba(Ce,Zr,Y)O3-? electrolyte materials. The basicity of the oxide ions is identified as a key parameter for proton uptake, it is modified by the cation composition (substitution of Ba by Sr or La decreasing [OHO.], partial substitution of Fe by Zn increasing it). The maximum [OHO.] of 10% at 250 °C was found for (Ba0.95La0.05)(Fe0.8Zn0.2)O3-? [2]. The proton concentration of Ba-rich cathode materials is expected to allow for an extension of the reactive zone beyond the three-phase boundary. Quantitative analysis of oxygen stoichiometry and proton uptake shows a significant hole-hole and hole-proton interaction [3]. This non-ideality can be related to a partial delocalization of holes from the transition metal to the oxide ions, which affects also the protons by decreasing the oxide ion basicity. Quantitative modelling of this issue is discussed. Such interactions are key to understand the differences in cathode versus electrolyte materials proton uptake. [1] D. Poetzsch et al., Farad. Disc. 182 (2015) 129 [2] R. Zohourian et al., in preparation [3] R. Zohourian et al., ECS Transact, 77(10) (2017) 133

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Interface and Surface Phenomena (V) : Dolors Pla and Stephen Skinner
Authors : Juergen Fleig
Affiliations : TU Wien, Institute of Chemical Technologies and Analytics, Vienna, Austria

Resume : Fast oxygen surface exchange is of vital importance in solid oxide fuel or electrolysis cells and many studies investigated the dependence of its kinetics on external experimental parameters (temperature, partial pressure, applied voltage), sample geometry or microstructure (porosity, grain size, etc.), and sample composition. Also the exact surface chemistry and the strain state affect the oxygen exchange rate. Moreover, kinetic models have to include point defects, which themselves depend on external experimental parameters, composition, etc.. Owing to this complex situation, the oxygen exchange kinetics of oxides remains a strongly debated topic and novel experimental or theoretical approaches are essential for further progress. In this contribution, it is considered how some rarely investigated factors affect the oxygen exchange rates of oxides. i) The role of dislocations in Sr-doped LaMnO3 (LSM) thin films is discussed. ii) The relevance of defects on the oxygen exchange of (La,Sr)FeO3-x (LSF) is evaluated from I-V measurements. iii) Measurements on SrTiO3 (STO) upon UV illumination give further information on the role of electronic defects. iv) The dependence of oxygen exchange on the electrode thickness is investigated for (La,Sr)CoO3-x (LSC) films of 3-100 nm thickness. Here, a novel tool comes into play, in-situ impedance spectroscopy during pulsed laser deposition (I-PLD). v) The same tool allows a detailed analysis of kinetic changes caused by growth of hetero-layers. These I-PLD measurements also revealed existence of a still unknown factor modifying the oxygen exchange kinetics: Growing LSC films exhibit extraordinarily active surfaces with oxygen exchange resistances much lower than ever observed in ex-situ experiments.

Authors : Christian Berger (1), Rotraut Merkle (2), Benjamin Stuhlhofer (2), Christian Gspan (3), Edith Bucher (1), Joachim Maier (2), Werner Sitte (1)
Affiliations : (1) Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria; (2) Max Planck Institute for Solid State Research, Heisenbergstraße 1, DE-70569 Stuttgart, Germany; (3) Institute of Electron Microscopy and Nanoanalysis (FELMI), Graz University of Technology & Graz Centre for Electron Microscopy (ZFE), Austrian Cooperative Research (ACR) Steyrergasse 17, A-8010 Graz, Austria;

Resume : Rare earth nickelates from the Ruddlesden-Popper (RP) series Lnn+1BnO3n+1 with Ln=La, Nd, Pr and B=Ni show exceptionally high oxygen diffusivities, high catalytic activity for oxygen reduction, and good electronic as well as ionic conductivities. Previous investigations on first order (n=1) RP-type rare earth nickelates demonstrated that the highest surface exchange rates are obtained for Pr2NiO4+? [1]. In the present study, the effect of partial substitution of Ni by Co in Pr2NiO4+? is investigated to further improve the surface oxygen exchange kinetics. In order to gain a deeper understanding of the oxygen exchange process in Pr2NiO4+? and Pr2Ni0.9Co0.1O4+?, dense thin film microelectrodes were prepared by pulsed laser deposition. The individual resistive and capacitive processes were investigated with electrochemical impedance spectroscopy as function of the oxygen partial pressure (1×10-3?pO2/bar?1) and temperature (550?T/°C?850). It was shown that B-site cation doping with small amounts of cobalt lowered the electrode resistance. The surface exchange coefficient kq calculated from the resistance of the electrode semicircle increased from kq = 2×10-7 cm s-1 for Pr2NiO4+? to kq = 5×10-8 cm s-1 for Pr2Ni0.9Co0.1O4+? at 850°C and 1×10-3 bar pO2. The observed exponents of the oxygen partial pressure dependence of kq are 0.73 for Pr2NiO4+? and 0.58 for Pr2Ni0.9Co0.1O4+? at 850°C. [1] C. Berger et al., Solid State Ion. 316 (2018) 93.

Authors : David N. Mueller(1,2), Daniel S. Bick(2,3), Jakub Drnec(4), Agnieszka Poulain(4), Daniel Többens(5), Hendrik Laufen(2,3), Leonard Diekman(2,3), Theodor Schneller(2,3), Slavomir Nemsak(1,6), Stefan Cramm(1), Felix Gunkel(2,3), Rainer Waser(1,2,3), Claus M. Schneider(1), Ilia Valov(1,2,3)
Affiliations : (1) Peter Grünberg Institute, FZ Jülich, D-52425 Jülich, Germany; (2) JARA ? Fundamentals of Future Information Technology, FZ Jülich, D-52425 Jülich, Germany; (3) Institute for Materials in Electrical Engineering and Information Technology (IWE2), RWTH Aachen University of Technology, D-52074 Aachen, Germany; (4) ID31, European Synchrotron Radiation Facility, FR-38043 Grenoble, France; (5) KMC2, Helmholtz-Zentrum Berlin für Materialien und Energie, D-12489 Berlin, Germany; (6) Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Resume : The perovskites structures? unmatched capability to accommodate virtually the whole periodic table of elements in the cation sublattice suggests the ability to tune the electronic and ionic defect structure towards favorable electrocatalytic activity by careful choice of the chemistry. Many favorable choices of chemistry, however, may lead to a departure from the ideal cubic perovskite structure, be it in the form of a complete decomposition or more subtly by ordering phenomena in either sublattice, impacting defect and electronic structure profoundly. One boiler plate example is the double perovskite PrxBa1-xCoO3-? (PBCO) where A-site as well as vacancy ordering may take place. In this work, we investigate the whole compositional space of PBCO in the form of active catalyst assemblies with sophisticated structural and spectroscopic methods to assay the phase relations and their impact on electronic and defect structure and with that the electrocatalytic activity. We find the anticipated transition from the hexagonal polytype in BaCoO3 to a cubic structure, and additionally the formation of superstructures along the substitution series, with the A-sites ordering at x = 0.6. These relations have profound impact on defect and electronic structure and surprisingly, aliovalent A-site substitution as well as the hexagonal to cubic transition only has a miniscule effect on the electrocatalytic efficiency, contrary to the A-site ordering showing a considerable one.

Authors : M. Weber, C. Hausner, D. N. Müller, D. Bick, T. Schneller, R. Waser, I. Valov, and F. Gunkel
Affiliations : IWE2 and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany; PGI, Forschungszentrum Jülich GmbH, Jülich, Germany;

Resume : In depth understanding of the atomic processes taking place at the interface of catalyst and electrolyte is essential for optimizing catalytic properties of catalysts for electrochemical water splitting. This requires defined model systems that provide defined and tunable structural and electrical properties and, at the same time, possess electrochemical performance compatible with state-of-the-art compounds. Epitaxial thin films are one crucial way of generating thin films and surfaces with defined phase and crystallographic orientation as well as defined surface morphology and roughness. We discuss the structural and electrochemical properties of epitaxial cobaltite thin films, synthesized in growth-controlled phases involving cubic perovskites as well as oxygen-vacancy ordered double-perovskites. The electrochemical properties are shown to have little dependence on the bulk structure of the thin film, while electrical conductivity and cation stoichiometry seem to be key for increased catalytic performance. We compare (Pr0.5Ba0.5)CoO3?d and (La0.4Sr0.6)CoO3?d thin films and show that achievable current densities can be increased by one order of magnitude (>150mA/cm2) by changing the cation composition, while maintaining atomically defined step terrace structure.

Authors : Yongliang Yong
Affiliations : 1 College of Physics and Engineering, Henan Key Laboratory of Photoelectric Energy Storage Materials and Applications, Henan University of Science and Technology, Luoyang 471023, China 2 Kathleen Lonsdale Materials Chemistry, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom

Resume : Motivated by the recent realization of cluster-assembled nanomaterials as gas sensors, first-principles calculations are carried out to explore the stability and electronic properties of cluster-assembled nanowires based on X12Y12 (X=Zn, Ga, Al, Y=O, N) clusters cluster-assembled nanowires and the adsorption behaviors of environmental gases on the X12Y12-based nanowires. Our results indicate that the ultrathin X12Y12 cluster-assembled nanowires have semiconducting electrical properties with direct energy gaps, and are particularly thermodynamic stable at room temperature. By analyzing the adsorption energy, adsorption types (chemisorption or physisorption), charge transfer, the adsorption behavior of the target molecules comparison with other common molecules, the change of electronic properties (particularly, DOS, band structures, and electric conductivity), the recovery time before and after the adsorption, we can confirm that the Zn12O12-based nanowire is a potential candidate for gas sensors with high sensitivity and selectivity for NO and NO2 detection, and the Al12N12-based nanowire should be a highly sensitive CO and NO sensor with quick response as well as short recovery time, and the Ga12N12-based nanowire should be a promising gas sensor for CO, NO, and NO2 detection.

Defects & Transport Phenomena (III) : George Harrington and David Mebane
Authors : Pjotrs A. Zguns (ab), Andrei V. Ruban (bc), Natalia V. Skorodumova (ab)
Affiliations : a) Department of Physics and Astronomy, Uppsala University, Box 516, 75121 Uppsala, Sweden b) Department of Materials Science and Engineering, KTH Royal Institute of Technology, 10044 Stockholm, Sweden c) Materials Center Leoben Forschung GmbH, A-8700 Leoben, Austria

Resume : Here we present the phase diagram of \ce{Ce$_{1-x}$Gd$_{x}$O$_{2-x/2}$} (CGO), calculated by means of a combined Density Functional Theory (DFT), cluster expansion and lattice Monte Calro approach. Methodology is well tested in the whole range of concentrations ($x \equiv x_{\ce{Gd}} \leq 1$) and is reliable. In the thermodynamic equilibrium, we observe two transitions ($x_{\ce{Gd}}\gtrsim0.3$): an onset of oxygen-vacancy (\ce{O-Va}) ordering at \emph{ca.} 1300K--3300K ($x_{\ce{Gd}} = 0.3\text{--}1$), and then, below \emph{ca.} 1000 K, a phase separation into \ce{CeO2} and C-type \ce{Gd2O3} ($x_{\ce{Gd}} = 0\text{--}1$). We also model quenched systems, with cations immobile below 1500 K, and observe that immobilised cations does not prevent the C-type order. The boundary between C-type \ce{Va} ordered and fluorite solid solutions is found to be $x_{\ce{Gd}} \approx 0.27$. For smaller concentrations \ce{O-Va} sublattice freeze into a random-like state upon cooling. Transition temperatures for \ce{Va} ordering (thermodynamic and quenched) compare well with existing experimental data. Moreover, DFT calculations of quenched structures show that \ce{Va} ordering affects lattice parameter and relaxation of cations, in good accordance with recent experimental findings. We also estimate the effect of ordering and composition on cations' misorientation from ideal C-type structure. The effect of ordering on ionic conductivity is discussed. Altogether, current study provides a deep understanding of structure and ordering in CGO consistent with the body of experimental data and allows to rationalise it.

Authors : E. Sediva (1,2,3), A. Nenning (1,2,3), F.Messerschmitt (1,2,3), J.L.M. Rupp (1,2,3)
Affiliations : 1 Electrochemical Materials, Department of Materials, ETHZ, Hönggerbergring 64, 8093, Zürich, Switzerland 2 Electrochemical Materials, Department of Materials Science and Engineering, MIT, 77 Massachusetts Av.,02139, Cambridge, MA, USA 3 Electrochemical Materials, Department of Electrical Engineering and Computer Science, MIT, 77 Massachusetts Av., 02139, Cambridge, MA, USA

Resume : Strontium titanate, SrTiO3, is a wide band gap electroceramic that belongs to the most investigated perovskites. By introducing iron on the structural B site a perovskite-type solid solution is formed over the entire composition range from SrTiO3 to SrFeO3. The SrTi1-xFexO3-? system can be used in a variety of important applications such as oxygen permeation membranes, solid oxide fuel cell electrodes, oxygen sensors or as the switching oxide in resistive random access memories. Despite extensive studies on the mixed ionic-electronic conduction and oxygen exchange kinetics of SrTi1-xFexO3-? [1],[2], Raman spectroscopic studies are scarce in this system [3]. However, Raman can be a powerful tool to obtain information on local atomic arrangements in relation to the defect chemistry by correlating the spectra with the materials stoichiometry and composition. Here we firstly review insights on Raman spectra, defect chemistry and structural symmetry for the SrTi1-xFexO3-? solid solution system over the whole composition range in thin films and pellets. Secondly we interpret the Raman spectra as a function of the stoichiometry and composition. The experiments are carried out using an electrochemical cell where the stoichiometry can be controlled by an applied bias. The intensity and position of the Raman peaks associated to the oxygen vibrations around the iron are linked to the local atomic arrangements. These findings introduce a controlled method of probing oxygen vibration modes with Raman spectroscopy as a function of the materials stoichiometry, which can be applied to various functional oxide materials helping Raman spectra interpretation but also probing materials properties on the near order. In this way we highlight the importance of Raman spectroscopy to understand and probe defects in functional oxides and present a precursor for Raman in-operando experiments on the device level. 1. A. Rothschild, W. Menesklou, H. L. Tuller, and E. Ivers-Tiffe, Chemistry of Materials, 18, 2006. ? 2. W. Jung and H. L. Tuller, Advanced Energy Materials, 1, 2011. ? 3. M. Vracar, A. Kuzmin, R. Merkle, J. Purans, E. A. Kotomin, J. Maier, and O. Mathon, Physical Review B, 76, 2007. ?

Authors : S. Grieshammer, J. Koettgen, M. Martin
Affiliations : Helmholtz-Institut Münster, Forschungszentrum Jülich GmbH; Institute of Physical Chemistry, RWTH Aachen University

Resume : Doped ceria is of major technological interest in energy related applications like solid oxide fuel cells, solid state batteries, and the production of solar fuels. The presence of defects, their interactions and their mobility determine key properties of the material. Density functional theory (DFT) calculations can provide information about defect energies on the atomic scale while Monte Carlo (MC) simulations are able to predict properties like phase stability and conductivity. Combining both methods enables the prediction of macroscopic quantities from first principles calculations. In this talk an overview of our recent computational research on bulk properties of doped ceria is presented. This includes the calculation of the energies of migration for oxygen ions in different dopant environments as well as the mutual interaction of defects. In addition to the energies the influence of vibrational entropies to defect formation, interaction and migration are considered. Monte Carlo simulations based on the first principles results are conducted to predict the distribution of defects, their influence on the redox behaviour and the ionic conductivity. The calculations reveal a strong influence of the atomic scale defect interactions on the macroscopic properties. These interactions can explain the dependence of the ionic conductivity of doped ceria on the type of dopant and doping level due to trapping of oxygen vacancies by the dopant ions and blocking of the migration path. In addition, defect interactions are responsible for the increased reducibility of Gd or even Zr doped ceria compared to pure ceria. Our results underline the importance of the interactions between individual defects on macroscopic properties.

Authors : Stephan Waldow(1)*, Hans Wardenga(2), Andreas Klein(2) and Roger A. De Souza(1)
Affiliations : (1) RWTH Aachen University, Institute of Physical Chemistry, Landoltweg 2, 52062 Aachen, Germany; (2) Technische Universität Darmstadt, Institute of Materials Science, Jovanka-Bontschits-Str. 2, 64287 Darmstadt, Germany

Resume : Oxygen diffusion in acceptor-doped ceria, in which oxygen vacancies are responsible for diffusion, has been studied extensively. In contrast, the diffusion of oxygen in donor-doped ceria, in which oxygen interstitials are the dominant oxygen defects, has received little attention. In this study, we synthesised and characterised ceramic samples of CeO2 doped with 1 mol % Nb2O5. Two different experimental methods were used to probe the diffusion of oxygen. 1) 18O isotope exchange experiments with subsequently analysis by means of Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) were conducted. From these measurements, the tracer diffusion coefficient of oxygen was determined. The exchange experiments were conducted in a temperature range from 773 K to 973 K and with an oxygen partial pressure of 0.2 bar. 2) Electrical Conductivity Relaxation experiments, in the Van der Pauw, configuration, were carried out, at different temperatures ranging from 873 K to 1073 K and oxygen partial pressure ranging from 10-6 to 10-1 bar. From the relaxation curves the chemical diffusion coefficient of oxygen was determined. With the thermodynamic factor calculated from defect calculations, chemical diffusion coefficients were transformed into tracer diffusion coefficients, and these data compared with results from the isotope exchange experiments. The results show a similar temperature dependent behaviour for both experiments, with an activation enthalpy of oxygen tracer diffusion roughly 0.8 eV.

Authors : Zonghao Shen(a), Stephen Skinner(b), Tatsumi Ishihara(a), John Kilner(a,b)
Affiliations : (a)WPI-International Institute for Carbon-Neutral Energy Research (I²CNER), Kyushu University, Japan (b)Department of Materials, Imperial College London, London, UK

Resume : In oxygen transport membranes (OTM), the dense ceramic separation layer is a fundamental component and is intended to produce oxygen with high selectivity. To function with high efficiency, both high electronic and ionic conductivity are required as well as high stability and long durability over a wide range of oxygen partial pressure. Recently accumulated attention has been focused on exploring dual-phase composite materials in order to fulfil the requirements. Among all the essential criteria, transport properties are profoundly important aspects. The experimental techniques used to determine the oxygen transport kinetics in this work were Isotopic Exchange Depth Profiling (IEDP) and Secondary Ion Mass Spectrometry (SIMS) [1] combined with Low Energy Ion Scattering (LEIS) to investigate the surface behaviour of the materials. In this work the Lanthanum Strontium Chromium Ferrite (LSCrF)-Scandium Stabilised Zirconia (ScSZ) based dual-phase materials have been investigated. Diffusion measurements were firstly carried out at the macroscopic scale and the ?effective? diffusion kinetics were obtained. In order to achieve the optimal properties, variations on different compositions and microstructures have been carried out. Whilst the OTM can function effectively with the LSCrF-ScSZ composite materials, the detailed mechanism by which the dense layer transports oxygen is unclear and the investigations on the oxygen diffusion mechanisms of the dual-phase composites are extremely limited. In oxygen diffusion studies at the microscopic scale using Focused Ion Beam (FIB)-SIMS, a synergistic effect between the two phases was observed in the composite materials: a decreased surface exchange coefficient (k) was observed for the mixed ionic and electronic conducting (MIEC) phase LSCrF while an enhanced k was obtained for the pure ionic conductor (ScSZ) compared to their corresponding isolated single-phase materials. Subsequently, the mechanism studies of the oxygen transport in the composites were performed on a specialised sample by applying IEDP, SIMS and LEIS techniques in order to study the different hypotheses in literature for the oxygen transport mechanisms of the dual-phase composite materials, i.e. cation inter-diffusion, spillover and self-cleaning effects. References [1] J. A. Kilner et al., Journal of Solid State Electrochemistry, 15 (2011) 861-876.

Authors : V.A. Sadykov, E.Yu. Pikalova, A.A. Kolchugin, E.A. Filonova, Z.S. Vinokurov, A.N. Shmakov, N.F. Eremeev, S.M. Pikalov, L.B. Vedmid?, D.A. Medvedev, V.D. Belyaev
Affiliations : Boreskov Institute of Catalysis SB RAS, 5 Akad. Lavrentieva av., Novosibirsk 630090, Russia; Novosibirsk State University, 2 Pirogova st., Novosibirsk 630090, Russia; Institute of High Temperature Electrochemistry UB RAS, 20 Akademicheskaya st., Yekaterinburg 620137, Russia; Ural Federal University, 19 Mira st., Yekaterinburg 620002, Russia; Budker Institute of Nuclear Physics SB RAS, pr. Akad. Lavrentieva 11, Novosibirsk 630090, Russia; Institute of Metallurgy, UB RAS, 101 Amundsena st., Yekaterinburg 620137, Russia

Resume : Materials with layered Ruddlesden?Popper structure having high oxygen mobility are promising for SOFC cathodes and oxygen separation membranes. This work aims at studying structural and transport features of Pr2-xCaxNiO4+? (x=0?0.6) synthesized by co-precipitation method and sintered at 1200 °C. Samples were characterized by in situ XRD using synchrotron radiation, TGA, oxygen heteroexchange with C18O2 and impedance spectroscopy. For Pr2NiO4+? a reversible Fmmm?I4/mmm phase transition occurs at ~480°C in air in agreement with TGA data, while for some doped samples irreversible I4/mmm?Fmmm phase transition occurs in Ar. Doping by Ca decreases the interstitial oxygen content in PCNO and, hence, the oxygen self-diffusion coefficient by 2 orders of magnitude up to x=0.3. At higher Ca content three channels of fast, slow and very slow oxygen diffusion with typical D* values being ~ 10-11, ~ 10-13 and ~ 10-16 ? 10-14 cm2/s at 430 °C were revealed corresponding to cooperative mechanism of migration, hampered cooperative migration in near-dopant positions and migration via vacancy mechanism in perovskite layers, respectively. The ionic conductivity remains rather high (~10-3?10-1 S/cm) being attractive for the practical application. Total conductivity varies non-monotonously with Ca content in the range of 60 -130 S/cm at 700°C reaching a maximum at x=0.5. Support by Russian Science Foundation (Project 16-13-00112) is gratefully acknowledged.


Symposium organizers
Albert TARANCONCatalonia Institute for Energy Research - IREC/ICREA

Jardins de les Dones de Negre, 1, Planta 2, E-08930, Sant Adrià del Besòs, Barcelona, Spain

+34 933562615
David S. MEBANEWest Virginia University

Morgantown, WV 26506-6106, USA

+1 (304) 293 3426
Mónica BURRIELCNRS – Grenoble INP Minatec

Laboratoire des Matériaux et du Génie Physique (LMGP) UMR 5628 3, Parvis Louis Néel MINATEC CS 50257 38016 Grenoble cedex 1 France
Regina DITTMANNForschungszentrum Juelich GmbH

Wilhelm-Johnen-Straße, Juelich, Germany

+49 2461 61 4760