Energy & functional materials: high pressure, high temperature synthesis & characterization
The relation between electronic structure and the crystallographic atomic arrangement is one of the fundamental questions in condensed matter physics and inorganic chemistry. Since the discovery of the atomic nature of matter and its periodic structure, this has remained as one of the main questions regarding the very foundation of solid systems. Needless to say this has also bearings on physical and chemical properties of matter, where again the relation between structure and performance is of direct interest.
High-pressure science is a fast developing new field in condensed matter physics and may even be regarded as the exploration of an entirely new dimension. This is to a large portion of course due to the development of the diamond anvil cell (DAC) technique with which one can easily control the pressure for systems of interest in the range of several mega bars and due to increasingly sophisticated synchrotron facilities to observe some of the drastic changes effected in the physical properties. With pressure, we can tune electronic, magnetic, structural and vibrational properties of condensed matter for a wide range of applications. ``Inert gases'' cease to be noble and inert, and can form stoichiometric compounds; likewise, normally unreactive transition metals can form alloys with alkali metals; silicate tetrahedral frameworks, the basis of rock-forming minerals, are destroyed and replaced by silicate octahedra; carbon rings, basic structural units of polymer and organic chemistry, become unstable and are replaced by diamond-like structures. High-pressure research has been predicted to ultimately even lead to the establishment of a new Periodic Table, one which has the same elements but completely redefined physical and chemical behaviors at megabar pressures. In this sense, the field of high pressure could indeed establish itself as a dimension in physical science on a par with temperature (low- and high-temperature physics) and composition (chemistry and materials science). First of all the exploration of the megabar pressure range is highly interesting by itself, where new physics and chemistry can be expected. Second, the general problem about the equation-of-state in this pressure range is highly significant for a vast number of materials. The underlying mechanisms determining the geometrical arrangement of atoms can be elucidated by the study of matter at extreme conditions, probing a new range of electron densities. One example where high pressure can play important role, for example for search of new high Tc superconductors or Hard materials. Materials under pressure change their forms and the superconducting state of a material is strongly linked to these structural phase transition. Pressure enhances electron-phonon interactions and the corresponding critical temperature (Tc). An important byproduct from this meeting at EMRS (September, 2017) could lead to an improved understanding and performance of materials at ambient and extreme conditions.
Hot topics to be covered by the symposium:
- Energy materials
- Topological insulators
- Hard materials (Carbon based materials)
- Hydrogen densed materials
- Functional oxides
- Dilute magnetic semiconductors
Confirmed list of invited speakers:
- Cheng-Chien Cheng (Stanford University, USA)
- Jiun-Haw Chu (University of Washington, USA)
- Van Veenendaal, Michel (Northern Illnois University, USA)
- Hasan Yavas, (Deutsches Elektronen-Sycnhrotron (DESY), Germany)
- Hans-Christian Wille, (Deutsches Elektronen-Sycnhrotron (DESY), Germany)
- Maria Baldini, (HP Syn@ Advanced Photon Source, USA)
- Yu Lin, (Stabford University, USA)
- ChunLei Wang (Florida International University, USA)
Tentative list of scientific committee members:
- B. Johansson, KTH, Stockholm, Sweden
- S.M. Sharma, Bhabha Atomic Research Center (BARC, India)
- H.D. Hochheimer, Colorado State University, USA
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High energy materials : Yang Ding
Authors : Chunlei Wang
Affiliations : Department of Mechanical and Materials Engineering Florida International University
Resume : Conventional electrochemical double-layer capacitors (EDLCs) are well suited as power sources for devices that require large bursts of energy in short time periods. However, EDLCs suffer from low energy densities as compared to their battery counterparts, which restrict their applications in devices that require a simultaneous supply of high power and high energy. In the wake of improving the energy density of EDLCs, the concept of hybridization of lithium-ion batteries (LIBs) and EDLCs has attracted considerable attention in recent years. Such a hybrid known as a Lithium-ion capacitor (LIC) comprises a Li-ion intercalating anode and a fast charging-discharging EDLC cathode. Although quite ideal in theory, such a system poses major challenges, most of which are a result of the mismatch between the specific capacities and power densities of the LIB and EDLC electrodes. In this talk, the challenge and our recent progress on developing various on-chip energy storage and power generation systems will be discussed. We have demonstrated that high performance nanocomposites enabled carbon micropillar arrays as well as TiN passivated porous Si could be two promising platforms for on-chip application. In addition, a hybrid capacitor that utilizes a Li4Ti5O12 (LTO) based anode and a graphene and carbon nanotube (G-CNT) composite based cathode will also be highlighted.
Authors : Nesrin Horzum
Affiliations : ZAC de courtaboeuf, Izmir Katip Celebi University, 3 avenue du Canada, 91940 LES ULIS, France
Resume : A power demand of the electronics has created a great interest in research and developments of advanced rechargeable battery systems. Li-ion batteries (LIBs) are one of the most significant energy storage systems because of their benefits such as higher energy density, longer cycle life, higher voltage compared to the other rechargeable batteries (e.g lead acid, Ni-Cd batteries.)  For the production of LIBs with the superior electrochemical property, type of materials used for LIBs components plays an important role. Polymers and transition metal oxides are commonly used as electrolyte and/or active electrode materials due to their flexibility, safety and availability . LiCoO2 is the most popular choice for microscale technology such as mobile phones, laptops due to its high specific energy, long cycling life, ease of production. Compared to the electrode materials in microscale, nanoscale materials (e.g. nanofibers, nanoparticle etc.) have attracted attention to produce active electrode materials for LIBs owing to their fast transport of Li ion by shorter diffusion path and high mass/charge. Particularly, nanofibers provide a much lower charge transfer resistance between electrolyte and electrode materials. Therefore, LIBs might be much safer and have faster solid state diffusion. Nanofibers can be easily fabricated on a large scale by electrospinning providing cost effective approach and structural characteristics such as high surface-to-volume ratio, porosity and interconnectivity. We have investigated electrochemical performance of LIB consist of LiCoO2 nanofibers as cathode and Li2CoTi3O8 nanofibers as anode produced by electrospinning.  R. Yazami, In Nanomaterials for Lithium-Ion Batteries: Fundamentals and Applications; CRC Press, 2013.  Y. Guo, J. Hu and L. Wan. Nanostructured Materials for Electrochemical Energy Conversion and Storage Devices Adv. Mater., 2008 20, 2878-2887.
Authors : Donia Fredj (1,2), Florent Pourcin (2), Sadok Ben Dkhil (2), Christine Videlot-Ackermann (2) , Olivier Margeat (2) , Jörg Ackermann, Mohamed Boujelbene (1)
Affiliations : (1) Laboratoire Physico-Chimie de l?Etat Solide, LR11 ES51, Faculté des Sciences de Sfax, Université de Sfax, BP 3071 Sfax, Tunisie; (2) Aix-Marseille University, Centre Interdisciplinaire de Nanosciences de Marseille CINaM, UMR CNRS 7325, Marseille
Resume : Organic-inorganic hybrid materials have been broadly investigated owing to their various properties used in optoelectronics and solar cell . Here, we report synthesis of two new organic-inorganic hybrid materials which are obtained by slow evaporation at room temperature using the same organic cation for two different molar ratio. These two compounds are characterized by X-ray diffraction, infrared and Raman spectroscopy, optical absorption and photoluminescence measurements. Additionally, we demonstrate that these compounds can be used in organic solar cells. In fact, the energy band gap of these materials was found to be closed to that used in interfacial layers  of some organic solar cells. By optimizing optical, electrical, and morphological properties of these new wide bandgap materials, bulk heterojunction solar cells with conversion efficiency exceeding 9 % are obtained in normal device structures with all-solution-processed interlayers in normal device structure. More importantly, the morphology and especially the surface roughness of these hybrid layers is crucial to obtain hole blocking behavior leading to fill factor up to 72 %.
Authors : S. Askari, N. Brenning and U. Helmersson
Affiliations : Department of Physics, Chemistry and biology (IFM), Linköping University, SE-581 83 Linköping, Sweden
Resume : Title: "Pulsed plasma process for growth and assembly of nanoparticles; 3D ‘on-the-fly’ assembly of functional nanoparticles into complex morphologies" Abstract: Hollow cathode pulsed plasma sputtering is a flexible and powerful technique for fabricating functionally important materials and architectures in micro- and nanoscales. We will present results on growth and 3D assembly of nanoparticles (NPs) including semiconducting (e.g. InN and ZnO), doped and plasmonic metal NPs. Control over NPs properties including opto-electrical properties has been achieved by fine tuning of the chemical composition and dopant concentration in ligand-free NPs of InN and ZnO. Widely tunable infrared plasmon absorption was observed, for the first time, in highly-degenerate InN NPs by varying nitrogen-deficient stoichiometries. Furthermore, the developed process allowed rapid integration of a variety of material’s NPs (e.g. metal oxides) into devices such as gas sensors and light detectors. For example, highly sensitive photodetectors with photo- to dark-current ratio ≥2.7x105 are fabricated from ultra-porous structures of NPs. Apart from NPs synthesis and device fabrication, we will focus on the unique opportunity provided by the plasma-based process for controlled self-assembly of functional NPs. Free-flying NPs extracted from the plasma are negatively charged which allows using long-range forces (e.g. electrostatic forces) for directed positioning of NPs. Using designed configurations of external electric forces allowed (computer aided) programmable assembly of NPs into 3D micro-structures. The method is highly flexible in terms of control over morphology and precise (nano-resolution) positioning of NPs. The developed gas-phase process opens a new route for micro- and nano-fabrication of novel materials, architectures and devices with prospect of industrial scale production.
Authors : Seong M. Cho, Soo Jeong Kim, Tea-Youb Kim, Juhee Song, Chil Seong Ah, Joo Yeon Kim, Sang Hoon Cheon, Hojun Ryu, Yong-Hae Kim, Chi-Sun Hwang, Jeong-Ik Lee
Affiliations : Electronics & Telecommunications Research Institute (ETRI)
Resume : Recently, the technologies related with the zero energy building are attracting much attention. Among these technologies, the smart window technology is considered as a core technology which can reduce the consumption of energy in buildings, such as heating, cooling and lighting energy by controlling the amount of solar energy entering the building. Switchable mirror devices based on reversible electrodeposition (RED) have been expected to be applicable to the smart windows. However, since the switchable mirror devices based on the RED have poor bistability, there is a distinct technological barrier in scale up of the device. In present research, we investigated the origin of the poor bistability in the RED based switchable mirror devices. It was confirmed that the Cu ion in the electrolyte of the RED based switchable mirror dissolve Ag film in combination with halide ions so the deposited Ag film cannot be stably present in presence of Cu ion in the electrolyte. Therefore, it is essential to remove the Cu ion from the electrolyte to obtain bistability of the device. However, without Cu ion it takes very long time to erase clearly the deposited Ag in erasing operation. We focused the structure characteristics as the origin of the difficulty in erasing operation and proposed a new structure of device with a counter electrode material which can act as a mediator. The detailed structure of the device and characterization will be presented and discussed.
Superconductivity : Yang Ding
Authors : Roman Marto?ák 1, Davide Ceresoli 2, Tomoko Kagayama 3, Yusuke Matsuda 3, Yuh Yamada 4, Erio Tosatti 5,6
Affiliations : 1 Department of Experimental Physics, Comenius University, Mlynská Dolina F2, 842 48 Bratislava, Slovakia; 2 CNR Institute of Molecular Science and Technology (ISTM), via Golgi 19, 20133 Milan, Italy; 3 KYOKUGEN, Graduate School of Engineering Science, Osaka University, Machikaneyamacho 1-3, Toyonaka, Osaka 560-8531, Japan; 4 Department of Physics, Faculty of Science, Niigata University, 8050, Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan; 5 International School for Advanced Studies (SISSA) and CNR-IOM Democritos, Via Bonomea 265, I-34136 Trieste, Italy; 6 The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, I-34151 Trieste, Italy
Resume : BaBiO3 is a mixed-valence perovskite which escapes the metallic state through a Bi valence (and Bi-O bond) disproportionation or CDW distortion, resulting in a semiconductor with a gap of 0.8 eV at zero pressure. The evolution of structural and electronic properties at high pressure is, however, largely unknown. Pressure, one might have hoped, could reduce the disproportionation, making the two Bi ions equivalent and bringing the system closer to metallicity or even to superconductivity, such as is attained at ambient pressure upon metal doping. We address the high-pressure phase diagram of pristine BaBiO3 by ab initio DFT calculations based on GGA and hybrid functionals in combination with crystal structure prediction methods based on evolutionary algorithms, molecular dynamics and metadynamics. The calculated phase diagram from 0 to 50 GPa indicates that pristine BaBiO3 resists metallization under pressure, undergoing instead at room temperature structural phase transitions from monoclinic I2/m to nearly tetragonal P-1 at 7 GPa, possibly to monoclinic C2/m at 27 GPa, and to triclinic P1 at 43 GPa. Remarkably, all these phases sustain and in fact increase the inequivalence of two Bi neighboring sites and of their Bi-O bonds and, in all cases except semimetallic C2/m, the associated insulating character. We then present high-pressure resistivity data which generally corroborate these results, and show that the insulating character persists at least up to 80 GPa, suggesting that the C2/m phase is probably an artifact of the small computational cell. References:  R. Marto?ák et al., arXiv:1704.04098, Phys. Rev. Mat., in press.
Authors : Myung Joon Han
Affiliations : Department of Physics, Korea Advanced Institute of Science and Technology (KAIST)
Resume : GaTa4Se8 has been known as a ‘paramagnetic Mott’ insulator and exhibits superconducting transition under pressure. Its low temperature behaviors found in susceptibility and specific heat have not yet been clearly understood. The important first step to study these phases and the relationship between them is to identify the electronic structure and the nature of its magnetic moment if there is any. By using first-principles band structure calculation and resonant inelastic x-ray scattering technique, we show that GaTa4Se8 is a novel ‘Jeff=3/2 Mott’ insulator in which spin-orbit interaction plays a key role to form a gap together with electronic correlation. Based on this new picture, we will revisit and discuss the intriguing behaviors previously reported in this material and will compare with other related materials.
Authors : Yang Ding (firstname.lastname@example.org)
Affiliations : Center for High Pressure Science and Technology Advanced Research, Beijing, 100094, China
Resume : High temperature superconductivity (HTSC) is one of the most important discoveries at contemporary condensed matter physics. However, its mechanism is still unclear. One way to approach this problem is to search for the controlling parameters of HTSC transition temperature Tc. In this presentation, we will introduce a novel type stripe phase in Bi2212 that is revealed by nano-imaging technique. Intriguingly, the evolution the stripe phase is in coincidence with the change of Tc, which implies a correlation between the Tc and the optimal inhomogeneity in the cuprate.
Authors : Ziya Wang, Fengping Wang
Affiliations : Department of Physics, University of Science and Technology
Resume : In this report, we summarize our series work of the properties of Nano MnO2 composite. Firstly, we have investigated a high-performance MnO2/Ni(OH)2 foam (MnO2/Ni(OH)2@NF) electrode material prepared. In this novel hierarchical design, nickel foam with a sheath of mesoporous Ni(OH)2 networks is coated with interconnected MnO2 nanosheets, which produces a highly porous reticular oxide/hydroxide/metal composite structure. The synergistic effects were employed to study the competitive advantages of MnO2/Ni(OH)2@NF electrode. Namely, 3D nickel foam serves as highly conductive backbone for deposition of nanostructured MnO2/Ni(OH)2 composite film, which provides the high accessibility of electrolytic ions for shorten diffusion paths. Secondly, we have designed interlinked multiphase Fe-doped MnO2 nanostructures to enhance the electrochemical properties. These hierarchical hollow microspheres assembled by interconnected nanoflakes, and with plenty of porous nanorods radiating from the spherical shells were hydrothermally obtained. The supercapacitor electrode prepared from the unique construction exhibits outstanding specific capacitance of 267.0 F g−1 even under a high mass loading (∼5 mg cm−2). Obviously improved performances compared to pure MnO2 are also demonstrated with a good rate capability, high energy density (1.30 mW h cm−3) and excellent cycling stability of 100% capacitance retention after 2000 cycles at 2 A g−1. The synergistic effects of alternative crystal structures, appropriate crystallinity and optimal morphology are identified to be responsible for the observations. Thirdly, we present an ingenious approach to directly realize a self-assembled mono/few layered MnO2 nanomesh architecture by a simple in situ redox reaction between KMnO4 solution and a sacrificial carbon template. Electron microscopy, X-ray diffraction and spectroscopy results strongly suggest that the interconnected MnO2 nanosheets are separated into the individual layers. The synthesized graphene-like MnO2 nanomesh electrode exhibits a substantially increased specific capacitance (516.7 F g−1) with excellent cycle stability and coulombic efficiency, which is among the highest reported values of a pure MnO2 electrode with similar loading mass and demonstrates the promising potential supercapacitor and battery applications.
High pressure and high temperature synthesis : Roman Martonak
Authors : Genady Komisarchik, David Fuks and Yaniv Gelbstein
Affiliations : Department of Materials Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel
Resume : In an attempt to reduce the reliance on fossil fuels, associated with severe environmental effects, the current research is focused on the identification of the thermoelectric potential of n-type PbTe alloys doped with small amount of Ti. Pb1-xTixTe alloys, with x values of 0, 0.1, 0.3, 0.5, 1, 2, and 3% were synthesized from pure elements by arc-melting under argon atmosphere. After a homogenization process done using a rocking furnace, the cast ingots were grinded into powder, and subsequently hot pressed under a mechanical pressure of 25MPa at 550°C for 60 minutes, resulting in high density values of >95% of the theoretical density. An impressive maximal dimensionless thermoelectric figure of merit ZT of 1.2 was obtained upon 0.1 at% Ti doping at 500 °C, indicating a 9% efficiency enhancement compared to undoped PbTe. Density Functional Theory (DFT) calculations demonstrate that Ti concentration of ~1.4 at% in the Pb sublattice maximize the thermoelectric power factor. Using combined DFT and statistical thermodynamic approach, the actual Ti solubility limit in PbTe was found to be ~0.3 at% and in agreement with the experimentally observed appearance of a secondary intermetallic TiTe2 phase. It is demonstrated that Ti doping fractions lower than the solubility limit are expected to provide close to maximal power factor values. This makes doping with Ti a promising opportunity for the generation of highly efficient n-type PbTe-based thermoelectric materials despite the well-known decrease of mobility of electrons due to the resonant states induced by Ti in the conduction band in this system.
Authors : Kun Yang, John T Fox, Robert Hunsicker
Affiliations : Lehigh University, Hunsicker Emission Services (HES), llc.
Resume : : Diesel Particulate Filter (DPF) has been widely used on commercial vehicles around the world. However, the DPF suffered large percentage of failures including melting, cracking. The effects of ash composition Na, K, Fe, Ca and Zn with porous cordierite DPF were investigated at elevated temperatures. Samples of unused cordierite substrate DPF were doped with sodium, potassium, and iron. The doped samples were heated in a thermal gravimetric analyzer to 300, 500, 900, and 1100oC. The resulting interactions were analyzed with scanning electron microscopy (SEM), x-ray diffraction, and wavelength dispersive x-ray microscopy (WDX). The alkalis and iron induced corrosion and degradation to the cordierite substrate at lower temperatures, than un-doped cordierite. The SiC nanowire was in-situ synthesized and characterized in order to substitute the current cordierite substrate. The synthesized SiC nanowire has higher chemical resistance and thermal shock resistance.
Authors : A. El hat, A. Hadri, C. Nassiri, M. Rouchdi, F.Z. Chafi, B. Fares, N. Hassanain, A. Mzerd
Affiliations : University Mohammed V, Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat, Morocco
Resume : SnxSy thin films with differents molar concentration (x=0.05 M, y=0; 0.03; 0.05; 0.07; 0.1 M) are deposited by spray pyrolysis technique on heated glass substrate at 350°C. The physical properties of the films are characterized by several techniques in order to study their structural, optical and electrical properties. From the study, we could understand that optimum molar concentration of the precursor solution to obtain device quality SnS thin film is x=0.05 M and y=0.05 M. It is observed from X-ray diffraction (XRD) analysis that the film is mainly composed with orthorhombic crystal structure with a preferred grain orientation along (111) plane. From optical measurements, a significant decrease in average optical transmission and the band gap value is 1.8 eV and having a very high absorption coefficient (105/cm). The Hall Effect electrical measurements show that the sample is p-type and the value of the electrical resistivity of SnS films is 2.75x10-2 (Ω.cm).
Authors : Laura Gonzalez, Mariam Pogosova, Fardad Azarmi
Affiliations : Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Moscow, Russia; Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Moscow, Russia; Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Moscow, Russia & Mechanical Engineering Department, North Dakota State University, Fargo, ND, USA
Resume : Inorganic pigments are widely known for thousands of years but there are still many ambiguities in their nature and characteristics, which opens several doors for further investigations. Contemporary pigments are widely being used and almost all artificial objects are colored. Unfortunately, modern manufacturing still utilizes toxic pigments, which basically made of lead, cadmium and chromium compounds. Therefore, contemporary pigments should have the low toxicity, high color stability, stability to the environmental factors, etc. Pigments based on the copper-doped apatite-type materials were discovered in 2001 with copper-doped strontium hydroxyapatite, which exhibited bright purple color. Later, the copper-doped barium and calcium hydroxyapatites were successfully discovered (with blue and magenta colors, respectively). Further, various cation-substituted and copper-doped calcium apatites were synthesized and analyzed. Thus, the influence of the anionic substitution was still not clear. Current work describes the new inorganic pigment based on the copper-doped strontium vanadate. All samples were synthesized using the high-temperature solid state method and quenched in air. The phase purity of the obtained samples was analyzed using the powder X-Ray diffraction. The crystal structure features of the obtained materials, including unit cell parameters, crystallographic sites and occupancies, were determined by the Rietveld refinement method. Color features were described using the diffuse reflectance spectroscopy and colorimetry.
Authors : Gökhan Topçu, Aslı Çelik, Mustafa M. Demir
Affiliations : İzmir Institute of Technology, Material Science and Engineering Department
Resume : Scaling by metal silicates represents a detrimental problem for geothermal and petroleum systems. The decrease of temperature and pressure during production reduces the solubility of siliceous species and causes remarkable precipitation, namely, scaling. This scaling problem is the most common and troublesome damage-causing event because deposition of silicates on the surface of important plant parts, such as pipes, separator vessels, and heat exchanger, blocks the fluid flow through the system and decreases the productivity. Organic inhibitors have been employed to minimize the formation of silicate scaling. In this study, artificial silica deposites have been synthesized in a pressurized reactor. The artificial precipitate was compared with the natural deposit in terms of elemental composition, crystal structure and morphology. We also synthesized homo and copolymers by using vinyl sulfonic acid, vinyl phosphonic acid, and acrylamide to be used as silicate inhibitors. Synthesized antiscalants and additional polymeric dispersants (PEG and PVA) were also tested under simulated underground conditions (high temperature and pressure) to reduce amount of insoluble silica. Soluble ions (Fe2+, Ca2+, Mg2+) and the amount of silica precipitates were traced to figure out the performance of the inhibitors employed in this study.
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Materials design : Chen Cheng-Chien
Authors : Daniel Tunega,a Tomá¨ Bučko,b,c Eva Scholtzova,c and Ali Zaouid
Affiliations : a. Institute for Soil Research, University of Natural Resources and Life Sciences, Peter Jordan-Strasse 82, A-1190 Vienna, Austria b. Slovak Academy of Sciences, Institute of Inorganic Chemistry, Dúbravska cesta 9, SK-84236, Bratislava, Slovakia c. Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská Dolina, SK-84215 Bratislava, Slovakia d. Université Lille Nord de France, LGCgE Lille1, Ecole Polytechnique de Lille, Cité Scientifique, Avenue Paul Langevin, 59655 Villeneuve d'Ascq Cedex, France.
Resume : Some layered phyllosilicates (e.g. kaolinite or smectites) are used for a preparation of new functional materials by intercalation of suitable organic species into interlayer space of clays that can be followed by a further chemical modification (e.g. grafting) of the internal layer surface. Phyllosilicate minerals such as talc, pyrophyllite, lizardite, and kaolinite have expandable layered structure, in which non-bonding dispersive interactions and hydrogen bonds are responsible for layer stacking stabilization. It represents a serious problem for a correct prediction of their structure and properties by conventional DFT functionals. In this work, a performance of several DFT methods was validated on models of talc, pyrophyllite, lizardite, kaolinite
Authors : Jiun-Haw Chu
Affiliations : University of Washington
Resume : In this talk I will outline a new technique to measure and control the properties of quantum materials using in-situ tunable strain fields. I will use iron based superconductors as an example to demonstrate how symmetry breaking strains enable us to probe the electronic nematic fluctuations, which appears to be correlated with the optimal superconducting transition temperatures. I will also show how strain could sensitively alter the transport behaviors of ZrTe5, a Dirac semimetal candidate. I will then discuss how the effects of strain in the context of a topological phase transition in this material.
Authors : Loay Elalfy, Prof. Dr. Ming Hu
Affiliations : Institute of Mineral Engineering, Department of Materials Modeling, RWTH Aachen University. Mauerstr. 5, D-52064 Aachen, Germany
Resume : Thermoelectricity is the phenomenon of conversion temperature gradient into electric current and vice versa. This phenomena is becoming more important as it reduces the losses during energy conversion, mainly due to heat. The figure of merit (ZT) for thermoelectric materials is the quantity that reflects how efficient a material is. ZT is inversely proportional to the thermal conductivity. Which means that for a better thermoelectric material, low thermal conductivity is to be achieved. In the literature, the thermal conductivity of HgTe (mercury telluride) was calculated for the zincblende (low pressure) and cinnabar (high pressure) phases by solving the Boltzmann transport equation using second- and third-order force constants calculated from Density Functional Theory. The calculations for the zincblende phase have shown an almost five times higher lattice thermal conductivity than the experimental values [Journal of Applied Physics 117, 245101 (2015)]. To better understand the discrepancy and the phonon scattering processes in both Zincblende and cinnabar phases, our recently proposed residual analysis method [Physical Review B 95, 195203 (2017)] is used and we find an unusual forth-order phonon anharmonicity. Time domain normal mode analysis was conducted to achieve more accurate values for thermal conductivity and gain better understanding the abnormal phonon transport in thermoelectric material HgTe.
Authors : Yan Song, Jianhong Dai
Affiliations : Harbin Institute of Technology at Weihai
Resume : Phase stability of Ti, Mg and Al at hydrostatic pressures upto 210, 270 and 390 GPa, respectively, was investigated by means of first principles. The influence of pressure on the phase transition is analyzed based on electronic structure calculations. Reliability of exchange-correlation potential under pressures was examined. It was found that the PAW-GGA potential with p semi-core states in valence electrons to be the best potential for various phases of Ti under high pressures. For titanium, the δ phase has similar structure to the β phase after full relaxation indicating a phase transition from δ to β could be occurred through all pressures considered here. At zero pressure, the ω phase is the most stable phase followed by α, γ, and β (δ) phases, and the phase transition order is ω→γ ()→β () with increasing of pressure, however, at high pressures (above 106 GPa), the phase stability is in the order of , and . Mg only keep stable in its ground structure (hcp) below 52 GPa and will then transform to bcc structure, which will be the most stable phase upto 270 GPa. Al can occur in its ground structure (fcc) under the hydrostatic pressure up to 143 GPa and then will transform to hcp structure as the increasing of pressure, while the bcc structure of Al will become the most stable phase above the pressure of 324 GPa. The evaluated critical pressures for phase transition in Ti, Mg and Al were well consistent with other theoretical and experimental results, implying the validity of our calculation approaches. Electronic structures are studied to clarify the influence mechanisms of pressure on phase transition. It is found that the bonding states are broadened in energy range with increasing pressure and the values of total DOS at the Fermi energy are gradually decreased in Ti systems, particularly in the and phases, which may be the reason that the β (δ) phase becomes the most stable phase at high pressure. However, it was not shown obvious changes in electronic structures in Mg and Al with increasing of pressures. The change of relative number of s, p, and d electrons are studied in detail. A connection between the change in number of valence electrons and the phase stability of all three metals was observed.
Thermodynamic properties of alloys : Ali Zaoui
Authors : Yu Lin
Affiliations : Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
Resume : Pressure dramatically alters a material’s physical and chemical properties over varying energy scales, adding a new dimension to energy-related, electronic, optical, mechanical, biological, and environmental applications. Halide perovskites are a class of versatile materials that have recently received extraordinary research attention as they exhibit remarkable structural, optical, and electronic properties applicable to a wide range of technologies needed for a sustainable energy future. In this talk, I will focus on how pressure can alter halide perovskites’ electronic landscapes, affect excited-state dynamics, and afford new structures not accessible through conventional syntheses. I will highlight two examples where pressure enables improved understanding of the origins of unusual phenomena and novel materials synthesis. (1) I will describe the first instance of pressure-induced room-temperature electrical conductivity arising in a two-dimensional Cu(II)-Cl organic-inorganic hybrid perovskite. (2) I will discuss drastic pressure-induced structural, electronic, and optical modifications to three-dimensional Pb-X (X = Br, I) hybrid perovskites and the first observation of metallization in (CH3NH3)PbI3.
Authors : Omer Meroz and Yaniv Gelbstein
Affiliations : Department of Materials Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
Resume : Due the finite nature and the damaging greenhouse gas emissions of fossil fuel there is a constant search for advanced technologies that take advantage of substitute, clean energy resources. An example of said technology is thermoelectrics. Thermoelectrics allows a conversion of waste heat into electricity. Compared to other energy conversion approaches, thermoelectric efficiency still has a way to go and thus needs to be further improved. The performance of thermoelectric devices is assessed by the dimensionless figure of merit ZT of the material, defined as ZT =α2σT/, where α, σ, and T are the Seebeck coefficient, the electrical and thermal conductivities, and the absolute temperature, respectively. The thermal conductivity is a combination of thermal conductivity via electrons, κe, and via phonons, κl. The main difficulty in improvement of the efficiency of a thermoelectric device is due to the complex relation between σ, α and Improving the performance of thermoelectric materials is usually done either by improving the power factor, α2σ, or by applying phonon scattering methods in order to lower the thermal conductivity. Bismuth–telluride-based alloys are of great importance not only as the best thermoelectric materials with the maximal ZT values close to unity near room temperature, but also due to the potential for further performance improvement. Since these alloys are highly anisotropic, there is a direct relation between the orientation and the thermoelectric properties of the ingots. Hence, higher ZT values can be achieved by improving the orientation anisotropy of the ingots. In this study Bi2TexSex compositions were electronically optimized by various CHI3 doping levels, preferred alignment of the crystallographic orientation, and lattice thermal conductivity minimization. The synthesis route included rocking furnace melting, energetic ball milling and hot pressing under optimal conditions for enhancement of the thermoelectric figure of merit, ZT, at temperatures higher than 200oC, commonly applied in low temperature power generation applications. The transport properties in perpendicular to the pressing direction were examined.
Authors : Peng ZUO (1,2) , Claire V. COLIN (1,2) , Holger KLEIN (1,2) , Pierre BORDET (1,2) , Emmanuelle SUARD (3), Erik ELKAIM (4), Céline DARIE (1,2)
Affiliations : 1 University Grenoble Alpes, Institut NEEL, F-38042 Grenoble, France 2 CNRS, Institut NEEL, F-38042 Grenoble, France 3 Institut Laue-Langevin, BP 156, F-38042 Grenoble, France 4 Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, F91192 Gif-sur-Yvette, France
Resume : Magneto-electric multiferroics are defined as a class of materials that combine the ferroelectric and the ferromagnetic properties in a single phase.  They are drawing considerable research interests not only for discovering various attractive fundamental physical phenomena but also for potential novel technological applications. However, either of the known Type I and Type II multiferroic materials has its own drawback as device materials.  Therefore, new materials with optimized properties useful for real applications are still to be found and are subject of active researches. Recently, the rather less explored doubly ordered perovskites AA’BB’O6 have attracted a growing interest [3-6]. The ordered AA’BB’O6 compounds exhibit a rock salt type ordering at the B-sites, and a layered ordering at the A-sites. The rock salt ordered B-sites are very common and have been observed in many A2BB’O6 compounds, while the latter layered ordering is very rare. The layered A-sites ordering is stabilized by the second-order Jahn-Teller distortions of the highly charged B’ cations , and the ordering in long range disappeared in the absence of the rock salt B-sites ordering . Theoretical investigations predicted that Hybrid Improper Ferroelectricity (HIF) could be induced in this class of materials . A polarization as large as ~16µC/cm2 was estimated from the structure of NaLaMnWO6 . In addition, the compounds AA’BB’O6 could order with magnetic cations at the B-site (e.g. NaLaMnWO6 , NaLaCoWO6 ), making the magneto-electric coupling possible. However, real examples of this class materials are very limited so far. In this study, we synthesized a series of doubly ordered perovskites NaLnCoWO6 (Ln= Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb) by solid state reaction, nine of which (Ln= Y, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb) are new phases prepared under high temperature and high pressure conditions. Their structural properties were investigated at room temperature by synchrotron X-ray powder diffraction and neutron powder diffraction. All of them crystallize in monoclinic structures, especially the nine new compounds have the polar space group P21 symmetry, as confirmed by second harmonic generation measurements. The P21 polar structures were decomposed and refined in terms of symmetry modes, demonstrating that the polar mode is induced by two non-polar modes in a manner of HIF. The amplitudes of these three major modes all increase with decreasing the Ln cation size. The spontaneous ferroelectric polarization is estimated from the neutron diffraction data of three compounds (Ln= Y, Tb, and Ho), and can be as large as ~20 µC/cm2. References:  Schmid, H. Ferroelectrics 1994, 162, 317-338.  Khomskii, D. Physics 2009, 2, 20.  Arillo, M. A. et al. J. Mater. Chem. 1997, 7(5), 801-806.  Knapp, M. C. et al. J. Solid State Chem. 2006, 179, 1076-1085.  King, G. et al. Chem. Mater. 2007, 19, 6451-6458.  Fukushima, T. et al. Phys. Chem. Chem. Phys. 2011, 13, 12186-12190.  King, G. et al. J. Mater. Chem. 2010, 20, 5785-5796.  Mulder, A. T. et al. Adv. Funct. Mater. 2013, 23, 4810-4820.
Authors : Tanvir Ahmed, Irina V. Belova, Graeme E. Murch
Affiliations : Center for Mass and Thermal Transport in Engineering Materials School of Engineering Faculty of Engineering and Built Environment The University of Newcastle Callaghan, NSW 2308 Australia
Resume : In this extensive study, the thermodynamic and diffusion properties of the liquid Ni-Al alloy are investigated over a wide temperature and concentration range by using molecular dynamics (MD) simulations. MD simulations are performed by using a reliable 2009 embedded-atom method (EAM) potential due to Purja Pun and Mishin. The results also permit the description of the temperature and concentration dependence of the thermodynamic factor for interdiffusion. In addition, the simulations permit analysis of the heat of transport in thermotransport. It is possible to estimate the contributions of Onsager off-diagonal terms for the temperature and concentration range under consideration. The results agree well with previous published experimental and simulation data where available. Keywords: Molecular Dynamics Simulation; Diffusion; Thermotransport; Ni-Al Alloys.
Authors : Qiaoshi Zeng
Affiliations : Center for High Pressure Science and Technology Advanced Research, Pudong, Shanghai 201203, People’s Republic of China.
Resume : Polymorphism, which refers to the occurrence of multiple chemically identical but structurally distinct phases, is a critical phenomenon in materials science and condensed matter physics. Diamond and graphite are well-known examples. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys (HEAs)1,2. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Herein, by employing an in situ high-pressure synchrotron radiation X-ray diffraction (XRD) technique in a diamond anvil cell, we discovered an unprecedented polymorphic transition from fcc (face-centered-cubic)-to-hcp (hexagonal-close-packing) in the prototype CoCrFeMnNi HEA. The transition is irreversible, and our in situ high-temperature synchrotron radiation XRD experiments at different pressures of the retained hcp HEA unambiguously revealed that the fcc phase was a stable polymorph at high temperatures, while the hcp structure was thermodynamically more favorable at lower temperatures. As the pressure increased, the critical temperature for the hcp-to-fcc transformation also rose. Reference: 1. Cantor B, Chang ITH, Knight P, Vincent AJB. Microstructural development in equiatomic multicomponent alloys. Mater. Sci. Eng., A 375–377, 213-218 (2004) 2. Yeh JW, et al. Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes. Adv. Eng. Mater. 6, 299-303 (2004).
High pressure phase transition : Wei Luo
Authors : Hasan Yavaş
Affiliations : PETRA III, Deutsches Elektronen-Synchrotron (DESY) Hamburg, Germany
Resume : Inelastic x-ray scattering (IXS) methods have been gaining popularity due to unique insight they provide into electronic and local structure of materials. Thanks to their high penetrating power, inelastic scattering of hard x-ray photons allows in-situ and in-operando investigations of complex systems. In-situ IXS techniques at high pressure and temperature are particularly useful in geophysical and geochemical applications for studying local chemical and electronic structures, like coordination and spin states. Additionally, IXS is used to explore low energy collective excitations like phonons, magnons, and charge transfer processes and their spatial dependence. Furthermore, the well-defined non-resonant inelastic cross section helps unambiguously determine ground state symmetries of correlated systems.
Authors : Cheng-Chien Chen
Affiliations : Department of Physics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
Resume : Elemental rare-earth metals exhibit intriguing properties arising from strong correlations effects due to partially filled f-electron shells. In this talk I will discuss the low-temperature structural and magnetic properties of Dysprosium under high pressure. In particular, the anomalous thermal expansion of Dysprosium will be investigated using first-principle calculations with noncollinear magnetism. I also will discuss the pressure-induced volume collapse of Cerium at room temperature. Model Hamiltonian simulations including hybridization effects and atomic multiplet interactions will be discussed together with recent X-ray Raman measurements.
Authors : Michel van Veenendaal
Affiliations : Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA,
Resume : An overview is given of the use of high-energy X-ray spectroscopy, such as X-ray absorption and resonant inelastic X-ray scattering (RIXS), to study the changes in the electronic structure of transition-metal compounds under high pressure. For iridates, RIXS can probe changes in the magnitude of the spin-orbit interaction and the branching ratio in X-ray absorption is sensitive to the ground-state expectation value of the spin-orbit coupling. The ground-state expectation value of the spin-orbit interaction is a combination of the jeff=1/2 spins that describe the magnetic ground state plus the jeff=3/2 spins that couple to the eg states. Observed experimental changes in the expectation values are often stronger than expected from changes in the lattice parameters. Additionally, using V2O3 as an example, the sensitivity of X-ray spectroscopy to insulator-metal transitions is discussed.
Poster presentation : Wei Luo
Authors : Yuan Jiao12, Seong Won Cho3, Suyoun Lee3, Kahyun Hur1, Myoung-Woon Moon1*, Aiying Wang2*
Affiliations : 1 Materials and Life Science Research Division, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea; 2 Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, P. R. China; 3Electronic Materials Research Center, Korean Institute of Science and Technology, Seoul 136-791, Republic of Korea
Resume : The hierarchical porous structures with controlled conductivity were fabricated by nesting soft templates on hard templates such as fabric structure. In this way, microporous structures of 4-6 nm were formed on macroporous structures of 10-15 μm in diameter. By immersing porous PET fabrics into resol/F127, in conjunction with a high-temperature treatment for carbonization, both the soft and hard templates were decomposed, while the precursor was carbonized. This created a conductive nature with resistivity less than 3.5×10-3 Ωm in ambient condition. Due to the capillary pressure in the porous structure, the contact area between liquid and porous carbon material has been greatly increased, which leads to a high sensitivity of the porous carbon material when used for concentration detection of methanol or hydrogen peroxide (H2O2). This new design concept could prove highly-effective for electroanalytical biosensors.
Authors : Abderrahim El hat, , Adil Hadri, Chourouk Nassiri, Fatima Zahra Chafi, Mustapha Rouchdi, Boubker Fares, Najem Hassanain, Ahmed Mzerd.
Affiliations : University Mohammed V,Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat, Morocco.
Resume : CdS thin film is deposited by spray pyrolysis technique on heated glass substrate at 350°C. The physical properties of the film are characterized by several techniques in order to study their structural, surface, optical and electrical properties. It is observed from X-ray diffraction (XRD) analysis that the CdS film is mainly composed with hexagonal Wurtzite structure with a preferred grain orientation along (101) plane. From optical measurements, the average optical transmission is 80 % of CdS sample and the band gap value is found 2.4 eV. The Hall Effect electrical measurements show that the sample is n-type and the value of the electrical resistivity 2.5x102 (Ω.cm) is obtained.
Authors : Ruslan Assylbayev, Aleksandr Lushchik, Evgeni Shablonin, Evgeni Vasil’chenko, Abdirash Akilbekov, Alma Dauletbekova, Maxim Zdorovets
Affiliations : Pavlodar State Pedagogical Institute, Mir Str. 60, 140000 Pavlodar, Kazakhstan; Institute of Physics, University of Tartu, W.Ostwald Str. 1, 50411 Tartu, Estonia; Institute of Physics, University of Tartu, W.Ostwald Str. 1, 50411 Tartu, Estonia; Institute of Physics, University of Tartu, W.Ostwald Str. 1, 50411 Tartu, Estonia; L.N. Gumilyov Eurasian National University, Munaitpasov 5, 010008 Astana, Kazakhstan; L.N. Gumilyov Eurasian National University, Munaitpasov 5, 010008 Astana, Kazakhstan; Institute of Nuclear Physics, Ibragimov Str. 1, 050032 Almaty, Kazakhstan, Ural Federal University, Mira Str. 19, 620002 Yekaterinburg, Russia
Resume : Being transparent in а wide spectral region, oxygen-free CaF2 single crystals are used as optical materials in many applications. The presence of impurities and radiation-induced structural defects greatly affect the properties of CaF2. The processes of defect creation by swift ions in fluorite remain poorly understood. The samples were irradiated with 0.23-GeV Xe ions (DC-60, Astana), 2.38-GeV Bi ions (UNILAC, GSI, Darmstadt) or 100-keV protons (KIIA 500 kV implanter, Helsinki) at 295 K.The damage was analyzed via induced optical absorption (IOA, 1.4-10.5 eV) and its thermal annealing in a stepwise regime (up to 1100 K). Three dominant complex IOA bands peaked at ~2.2, ~6.5, ~9.8 eV were registered. Experiments with photo- and thermal influence on IOA confirmed a complex structure of the 2.2 eV band associated with different F-type aggregates and Ca-colloids previously studied by many authors in additively colored crystals. The main IOA annealing stage occurs at 470-580 K, in parallel with the dissociation of the most stable hole centers – trifluoride molecules (peaked at ~ 6.5 eV). Of special interest is the IOA band at 9.8 eV which can be induced exclusively by swift heavy ions. This band is tentatively ascribed to electronic excitations nearby complex structural defects. The joint action of shock waves and decay/recombination of radiation-induced electronic excitations is responsible for the creation of novel defects with complex structure under Xe or Bi irradiation.
Authors : E. Alloa, V. Grande, S. Herbst, F. Würthner, S. C. Hayes
Affiliations : University of Cyprus, Department of Chemistry, Nicosia, 2109, Cyprus Universität Würzburg, Institut für Organische Chemie, Würzburg, 97074, Germany
Resume : Perylene bisimides (PBIs) are dyes and pigments known for combining high absorption and emission in the visible region with their thermal and photochemical stability. Non-conventional H-bonded aggregation driven by free-imide groups has been reported to promote alternative J-type aggregate formation in non-polar solvents. J-aggregates are highly desired thanks to their bathochromically shifted absorption and fluorescence (by exciton coupling), together with hyperchromicity and superradiance compared to the monomer. Herein we present the water soluble analogue PBI4 showing interesting aggregation in water and in solid state. Unlike hydrophobic precursors, PBI4 aggregates in water upon increasing temperature indicating an entropy-driven self-assembly. Temperature dependent Resonance Raman (RR) spectroscopy at different wavelengths was employed for the structural characterization of PBI4 in aqueous solution versus toluene and in aggregated thin films. In order to gain insights on the structure of the aggregate, theoretical calculations of the normal modes of PBI4 with the use of Gaussian were performed to correlate the varied vibrational fingerprint upon aggregation to specific structural changes. These assignments indicate a distortion of the perylene core upon aggregation, where the bonds along the perylene long axis lengthen and the ones perpendicular to that shorten, suggesting a head-to-tail arrangement. Complementary FT-IR measurements provides further information on the aggregation process.
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