ANIM 3: advances and enhanced functionalities of anion-controlled new inorganic materials
Based on the success of the 1st (E-MRS symposium T, Spring 2013) and 2nd edition (E-MRS GG, Spring 2015), this symposium will focus on the solid state chemistry and physics of mixed anion materials. Their vast application prospects and huge innovative potential will be promoted. Compared to the widely investigated oxides, they offer tremendous possibilities to tune the chemical bonding through multiple anions and the subsequent properties. ANIM 3 aims to cover a large domain from the synthesis to the understanding of the fundamental properties of novel devices based on enhanced properties offered by such materials.
The present E-MRS symposium aims creating a European forum for the different types of researchers necessary to promote this field (materials scientists, solid state chemists and physicists, analytical scientists and device design engineers – experimentalists and theoreticians). The symposium will facilitate interdisciplinary discussions within and between these “core groups”, thereby stimulating collaboration and thus it will strengthen the European and Worldwide activities in this expanding and particularly promising field.
The symposium’s scope will survey the mixed-anion materials landscape with emphasize on the following aspects:
- Searches for new perovskites, related materials, but also more exotic phases with the goal to expand and tune their functionalities and electronic properties from anion control (e.g. photocatalytic, luminescent materials, nonlinear optical materials, ferroelectric, ferromagnetic, semiconductive, thermoelectric, electroresistive, magnetoresistive, conductive transparent high temperature stable electrodes, solid state electrolytes, ionic conductors, dipole glasses, quasi-2-dimensional electron gases (Q2-DEG) in insulating hetero-interfaces etc…).
- Advances in synthesis techniques that have enabled the development of mixed anion materials, with emphasize on more efficient and environmental friendly methods.
- Computational approaches to accelerate new mixed anion materials discovery for various applications, to guide experimentalists. Theoretical studies to help current and future design of new (multi)functional materials. Theoretical concepts for novel physics expected to be derived from new functions and properties of coordinate covalent-bonding engineered ceramic material systems, epitaxial and polycrystalline thin films, glasses, single crystals, quantum size effects in nanoparticles and nanosized powders.
- Overviewing of anion-substituted inorganic materials in device development activities: state-of the-art characterization and electronic properties improvement based on heterostructures, interface phenomena, electrode interactions and various device prototypes demonstrations.
Hot topics to be covered by the symposium:
- Innovative synthesis routes for Anion-substituted New Inorganic Materials (ANIM) oxynitrides, oxyfluorides, oxyhydrides and other mixed anion materials (powders, nanomaterials, bulk ceramics, glasses, thin films and single crystals).
- Structural features and anion order of ANIM.
- ANIM-based (photo)catalyst materials.
- Optical properties: luminescence, nonlinear optical properties of ANIM materials.
- Feromagnetic, paramagnetic; paraelectric, high-K gate, ferroelectric, multiferroic properties of ANIM materials. ANIM-type semiconducting and highly conducting electrode materials.
- ANIM-based energy materials for production and storage of energy: solid electrolytes, fuel cell materials electrode materials, supercapacitor materials, battery materials, hydrogen storage materials, ionic conductor and thermoelectric materials.
- Band gap and electronic structure engineering from anionic substitution: Applications
- Theory, simulations and combinatorial approaches for design of new anion-controlled materials and prediction of their functionalities.
- Technical challenges in the analytical and functional properties characterization of ANIM materials
List of invited speakers:
- Evgeny V. Antipov (Lomonosov Moscow State University, Russia)
- Laurent Cario (IMN, CNRS, France)
- Simon Clarke (University of Oxford, UK)
- Alain Demourgues (ICMCB, Bordeaux, France)
- Joke Hadermann (University of Antwerp, Belgium)
- Katsuro Hayashi (Kyushu University, Japan)
- Hideo Hosono (Tokyo Institute of Technology,Yokohama, Japan)
- Ralf Riedel (TU Darmstadt, Germany)
- Aron Walsh (Imperial College London, UK)
- Patrick Woodward (The Ohio State University, USA)
Tentative list of scientific committee members:
- J. Paul Attfield (University of Edinburgh, UK)
- Laurence Croguennec (ICMCB, Bordeaux, France)
- Shiv Halasyamani (University of Houston, USA)
- Mike Hayward (University of Oxford, UK)
- Shinichi Kikkawa (Hokkaido University, Japan)
- Olivier Mentre (UCCS, Lille, France)
- Kenneth Poeppelmeier (Northwestern University, USA)
- Franck Tessier (ISCR, Rennes, France)
Selected papers will be published in a special issue of the journal "Solid State Sciences" (Elsevier).
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OXIDES / OXIDES-HYDRIDES / : Mike Hayward
Authors : Hideo Hosono
Affiliations : Materials Research Center for Element Strategy, Tokyo Institute of Technology, Japan
Resume : It is a grand challenge in materials science to realize valuable active functionality using abundant elements. Electron and hydrogen are the most simple and abundant species in space. Most of functionalities in oxides are obtained by tuning cations. In this talk I introduce our approach to electro-active functionality in oxide-based materials and intermetallic compounds bearing anionic electron and hydrogen as anions. Materials focused are ionic and intermetallic electrides for catalysts, iron oxypnictide superconductors and transparent amorphous oxide semiconductors for active layers in thin film transistors.
Authors : Olivier Hernandez 1, Gregory Geneste 2, Takeshi Yajima 3,4, Yoji Kobayashi 3, Masatoshi Okura 3, Kouhei Aidzu 3, Cédric Tassel 3, Serge Paofai 1, Clemens Ritter 6, Hiroshi Kageyama 3,5
Affiliations : 1 Institut des Sciences Chimiques de Rennes,Univ Rennes, France, 2 CEA DAM Ile-de-France (DIF), Arpajon, France, 3 Department of Energy and Hydrocarbon Chemistry, Kyoto University, Japan, 4 Institute for Solid State Physics, The University of Tokyo, Japan, 5 CREST, Japan Science and Technology Agency (JST), Japan, 6 Institut Laue-Langevin, Grenoble, France
Resume : Layered perovskite titanium oxyhydrides have been prepared by low temperature topochemical CaH2 reduction from Ruddlesden-Popper Srn+1TinO3n+1 phases (n = 1, 2) and structurally characterized by combined synchrotron X-ray and neutron diffraction data refinements. In the single-layered Sr2TiO3.91(2)D0.14(1) material, hydride anions are statistically disordered with oxides on the apical site only, as opposed to known transition metal oxyhydrides exhibiting a preferred occupation of the equatorial site. This unprecedented site selectivity of H- has been reproduced by periodic DFT+U calculations, emphasizing for the hydride defect a difference in formation energy of 0.24 eV between equatorial and apical sites. In terms of electronic structure, the model system Sr2TiO3.875H0.125 is found slightly metallic and the released electron remains mostly delocalized over several Ti atoms. On the other hand, hydride anions in the double-layered Sr3Ti2O6.20H0.12 material show a clear preference for the bridging apical site within the perovskite slabs, as confirmed by DFT calculations on the Sr3Ti2O6.875H0.125 model system. Finally, the influence of the B-site chemical nature on the hydride site selectivity for early 3d transition metals is theoretically explored in the single-layered system by substituting vanadium for titanium. The V3+ electronic polaron is suggested to play a role in stabilizing H- on the equatorial site in Sr2VO4-xHx for x = 0.125.
Authors : S. Cornelius, F. Nafezarefi, G. Colombi, S. Eijt, D. Chaykina, B. Dam
Affiliations : Chemical Engineering, Faculty Applied Science, Delft University of Technology, The Netherlands
Resume : Due to the large difference in electronegativity the nature of hydrogen in Rare Earth hydrides (REHx) is anionic. This results in a metal/insulator transition at a critical metal/hydrogen ratio of around 2.7. Recently it was found that upon exposure to air, porous YH2 (and REH2) films transform into a photochromic oxyhydride state [1,2]. By a combination of Rutherford backscattering and elastic recoil detection, we found that the photochromic nature is maintained over a wide compositional range described by the formula REO(x)H(3-2x) where 0.5 < x < 1.5. This implies that the Y/RE cation maintains the 3+ valence for all photochromic compositions. Moreover, it can be clearly distinguished from the non-photochromic hydroxides. We propose a corresponding structure model based on an fcc-unit cell where the O2- and H- anions partially occupy the tetrahedral and octahedral interstitial sites. . Our understanding of the photochromic properties is still limited. The optical excitation is clearly related to the bandgap, which varies with the O/H-ratio. Illumination induces a color neutral darkening over a wide wavelength range (from UV to mid-IR). We will discuss the physical mechanism of this effect based on recent data on the local structure obtained with EXAFS and muSR. References:  Mongstad et al., Solar Energy Materials & Solar Cells 95 (2011) 3596?3599  F.Nafezarefi et al., Appl. Phys. Lett. 111, (2017) 103903  S. Cornelius et al., J.Phys.Chem.Lett., submitted
OPTICAL PROPERTIES AND MIXED ANION : Shinichi Kikkawa
Authors : Katsuro Hayashi, Hiroshi Watanabe, Hirofumi Akamatsu, George Hasegawa
Affiliations : Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
Resume : Sevier reduction processes using metal hydride agents modify the chemical and structural properties of metal oxide crystals with different manners, depending on the host crystals and the process conditions. For example, the reduction of SrFeO3 preferentially eliminates O2- at axial sites in the FeO6 octahedra to convert to SrFeO2 with a planner four-coordinated Fe2+. This is regarded as the oxygen vacancy formation with trans-configuration in the octahedra. Herein, we focus on the metal hydride-reduction of BaSn1-xYxO3-x/2 with the primitive cubic perovskite structure and relevant defect chemistry. The sample color changed from white to yellow, red, and brown with keeping the cubic perovskite structure as the reduction proceeds. Partial reduction of Sn4+ to Sn2+ was observed by XPS. Chemical composition of a reduced sample with x = 0.3 was determined to be BaSn(IV)0.50Sn(II)0.20Y0.30O2.61H0.08 by Rietveld analysis of neutron diffraction data, implying that H- ion on the order of 10^21 cm-3 is incorporated in this sample. Moreover, high concentration of Sn2+ with a few tens of percent is formed. 119Sn Mössbauer spectra was analyzed by a DFT calculation of crystal models with oxygen vacancies, and revealed that 5s2 lone pair electronic states of Sn2+ is formed in the band gap above the valence band, and its electronic transition to the conduction band is responsible for the coloration. This defect is stabilized by oxygen vacancy pair with cis-configuration around the Sn2+
Authors : Daichi Kato, Ryu Abe, Hiroshi Kageyama
Affiliations : Department of Energy and Hydrocarbon Chemistry, Kyoto University, Japan
Resume : A layered oxychloride Bi4NbO8Cl is a visible-light catalyst for water splitting, with its remarkable stability ascribed to the highly dispersive O-2p orbitals in the valence band, but the origin of unique band structure remains unclear. We systematically investigate four series of layered bismuth oxyhalides, BiOX (X = Cl, Br, I), Bi4NbO8X (X = Cl, Br), Bi2GdO4X (X = Cl, Br) and SrBiO2X (X = Cl, Br, I) and found that Madelung site potentials of anions capture essential features of the valence band structures of these materials. The oxygen anion in the fluorite-like blocks (e.g. [Bi2O2] slab in Bi4NbO8C) is responsible for the upward shift in the valence band maximum, and the degree of electrostatic destabilization changes depending on building layers and their stacking sequence. This study suggests that the Madelung analysis enables a rough prediction or design of the valence band structures of bismuth and other layered semiconductors and is applicable even to a compound where DFT calculation is difficult to carry out. Bi 6s electrons also play an important role for elevating valence band maximum.
Authors : Hiraku Ogino, Yuki Iwasa, Kohei Yamanoi, Toshihiko Shimizu, Nobuhiko Sarukura, Jumpei Ueda, Setsuhisa Tanabe
Affiliations : Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Resume : The compounds containing multiple anions in a single phase is so-called mixed anion-compounds, and have been considered as a new frontier of inorganic materials. One of the advantages of the compounds are the formation of the specific structures such as layered as well as the properties originated from the structure. Recently we developed a series of layered compounds composed by semiconducting metal-chalcogenide layers and insulating oxide layers such as Sr2ScAgSeO3. These compounds show sharp exciton emission peaks near the band edge, and the stability of excitons at room temperature because of quantum confinement effect owing to their layered structure. The special feature of the system is the controllability of both combination of the elements and the stacking structures. These flexibility of the system offers to tune the band gap of the compounds, and structural difference gives different level of the quantum confinement effect as well as temperature stability of the luminescence. The chemical and structural flexibility of the layered structure has offered vast opportunities to raise the novel functionality of the materials. References:  Y. Iwasa, H. Ogino et al., Opt. Mater. 84 (2018) 205
Authors : Tong Wu,a Asako Ishikawa,Satoru Matsuishi
Affiliations : Materials Research Center for Element Strategy, Tokyo Institute of Technology,Japan
Resume : Compared to conventional host materials, hydride and hydride-based mixed-anion compounds are expected to produce larger centroid shifts due to nephelauxetic effect induced by hydride ligands. However, their poor stability in air and moisture limits their application. In the present study, we investigated the photoluminescence properties of air- stable oxyhydride Sr2LiSiO4H doped with Eu2+ and Ce3+. The Eu- and Ce-doped phosphors were synthesized by solid state reaction of oxide and hydride precursors under H2 atmosphere. Both compounds exhibit the shifting of excitation and emission bands into longer wavelength region than those in the oxyfluoride analogue Sr2LiSiO4F:RE (RE = Eu2+ ,Ce3+) and show the yellow and green luminescence under near-UV light of 375 nm, respectively. The red-shifts induced by F- to H- substitution are consistent with the results of constrained density functional theory calculations predicting the photo-excitation and emission energies of 4f?5d transitions. These results demonstrate that the substitution of H- to F- sites in oxyfluoride-based phosphor materials is a promising strategy to create novel phosphor materials which can be excited by near-UV LED.
Authors : Nathalie Vonrüti, Ulrich Aschauer
Affiliations : University of Bern, Switzerland; University of Bern, Switzerland
Resume : Polarity, for example in ferroelectric materials, can significantly increase a catalyst?s performance by improving charge-carrier separation. For photocatalytic water-splitting perovskite oxynitrides are promising materials due to their small band gaps as well as their suitable band edges that straddle the oxygen and hydrogen evolution potentials. Ferroelectricity can be induced by epitaxial strain in these materials. However, polar distortions also increase the band gap as was shown for epitaxially strained SrTiO3 . While this band-gap increase is small for oxides, our density functional theory calculations show a much larger increase for oxynitrides: The enhanced covalency due to reduced electronegativity of nitrogen compared to oxygen results in larger strain-induced polar distortions and therefore more strongly increased band gaps by up to 1.5 eV. The reduced electronegativity, which leads to a higher valence band in oxynitrides and therefore a band gap in the visible that is attractive for photocatalysis, thus also has a detrimental effect on photo absorption when polar distortions are present. This results in a trade-off between small band gaps and polarity. We will discuss different strategies on how to overcome this trade-off with mixed anion perovskite compounds, such as oxysulfides and oxyhydrides, which have not yet been considered for photocatalytic water-splitting. References:  RF Berger et al. PRL 107.14(2011):146804
DESIGN AND MODELING : James Rondinelli
Authors : Shunsuke Sasaki, Dalel Driss, Melanie Lesault, Elodie Grange, Jean-Yves Mevellec, Etienne Janod, Benoît Corraze, Sylvian Cadars, Maria Teresa Caldes, Catherine Guillot-Deudon, Stéphane Jobic, Laurent Cario*
Affiliations : 1 Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, Nantes, France
Resume : Layered transition metal compounds have been extensively investigated due to their unconventional electronic/magnetic properties. Topochemical reactions, which introduce/withdraw ions into/from host materials retaining their lamellar structures, serve as one of the most effective tools to design such low-dimensional materials. Despite their huge advances during the recent decade, most of topochemical reactions rely on redox activities of transition metal cations in host lattices so that their charge balance are respected throughout the process. Conversely the redox activity of molecular anions for topochemical syntheses remains almost unexplored. We demonstrate here that electron transfer from Cu0 to chalcogen dimers (Q2)2- (Q = S, Se) and concomitant Q-Q bond cleavage enable host lattices to accommodate Cu+ cations, yielding extended (CuQ) sheets . This concept is verified on various (Q2)2--containing materials with different cationic layers and chalcogen species. The general applicability of the concept beyond the reaction between dimer and copper will be also discussed. References:  S. Sasaki, D. Driss, E. Grange, J.-Y. Mevellec, M. T. Caldes, C. G.-Deudon, S. Cadars, B. Corraze, E. Janod, S. Jobic, L. Cario, Angew. Chem. Int. Ed., 57, 13618-13623 (2018).
Authors : Richard J. Saballos 1, Sheel Sanghvi 1, Jaye K. Harada 1,2, Ching-Hwa A. Chen 2, Prof. Steven D. Jacobsen 3,4, Kenneth R. Poeppelmeier, Sossina M. Haile 1,2,4, James M. Rondinelli 1,4
Affiliations : 1 Department of Materials Science and Engineering, Northwestern University, USA, 2 Department of Chemistry, Northwestern University, USA, 3 Department of Earth and Planetary Sciences, Northwestern University, USA, 4 Applied Physics Graduate Program, Northwestern University, USA
Resume : Pressure has been extensively used to synthesize new materials, induce phase transitions and control properties in many inorganic compounds . However, few studies have been carried out on the effects of pressure on the electronic and structural properties in oxyfluorides using first-principles methods. By combining density functional calculations and high-pressure Raman spectroscopy, we efficiently search for previously unknown phases predicted from theory and assess the structures experimentally. We used this methodology to study the pressure (0-10 GPa) effects on the experimentally known non-centrosymmetric phase of KNaNbOF¬5 . We predict that as pressure is increased, this material undergoes an isostructural phase transition with concurrent changes in its electronic structure . We explain these variations in the electronic properties as arising from variations in local chemical bonding. References:  L. Zhang, et al., Nat. Rev. Mat. 2, 17005 (2017)  M. Marvel, et al., J. Am. Chem. Soc. 129, 13963 (2007)  A G. Christy, Acta Cryst. B51, 753-757 (1995)
Authors : Silviya Ninova, Hassan Ouhbi, Ulrich Aschauer
Affiliations : Department of Chemistry and Biochemistry, University of Bern, Switzerland
Resume : The anion order in perovskite oxynitride materials presents an additional degree of freedom to tune the material’s properties. We have previously shown, based on density functional theory (DFT) calculations, that the anion order at the surface is different from the one in the bulk for LaTiO2N. Here we assess the thickness of this trans ordered surface layer and show how it affects the catalytic activity towards water oxidation. We also discuss peculiarities of the defect chemistry of oxynitride surfaces in a catalytic setup and the effect of defects on the catalytic activity. Finally, we show how new electronic functionality analogous to the celebrated LaAlO3/SrTiO3 interface may result from modulated anion order in oxynitride materials.
Authors : Batoul Almoussawi, Gauthier Lefèvre, Adlane Sayede, Angel Arevalo-Lopez and Houria Kabbour
Affiliations : Unité de catalyse et de chimie du solide (UCCS), France
Resume : The search for new phases with original properties is a major task in inorganic chemistry. Mixed anion compounds have proved their importance at this level and provide a rich chemistry to tune the properties. In the oxychalcogenides family for instance, LaOCuCh (Ch= chalcogenide) based systems are wide band gap semiconductors  and doped La2O2S provide inorganic phosphor materials .The main purpose of this work is to synthesize new mixed anion phases with innovative physical and chemical properties with emphasize on their potential optical properties. The idea is to draw on structural entities with mixed anions to formulate new phases with multiple advantages related to these characteristics (modulation of properties, strongly acentric entities with exacerbation of some properties...). Compounds such as Ba2In2Si3O10S or Ba2SiS5 inspired us for anionic modifications. The former exhibits a layered structure, and the later disconnected tetrahedra while both have large optical gaps . It is interesting to mention BaGeOSe2 because it exhibits acentric mixed anion entities GeO2Se2 that lead to enhanced NLO properties compared to the analogue oxide . In this work, the mixed anion compound with the formula Ba6SiInSe9I was successfully synthesized. The structure is composed of mixed tetrahedra Si4+/In3+ cations coordinated by selenide anions. Mixed Se2-/I- sites are found in the vicinity of Ba2+ cations. The structure . We will also discuss other original phases obtained during our prospection such as Ba2ZnInS4 that exhibits a 3D framework with isolated tetrahedra. The crystal structures will be correlated to the properties with support of DFT calculations, in particular the mixed anion bonding will be emphasized. References:  Unrevealed electronic and optical properties of the layered oxychalcogenides (LaO)CuCh (ch=S, Se, Te): A density-functional study. al., M.Shibghatullah et. s.l. : Japanese journal of applies physics, 2017, Vol. 56.  Vertex-linked ZnO2S2 Tereahedra in the oxysulfide BaZnOS: a new coordination environment for Zinc in a condensed solid. al., S.Broadley et. Oxford : Inorganic Chemistry, 2005, Vol. 44.  Face-shared octahedral dimer In2O7S2 in the noncentrosymmetric Barium Indium Silicate Oxysulfide Ba2In2Si3O10S. Guo, W.H et al. s.l. : european journal of inorganic chemistry, 2016.  Oychalchogenide BaGeOSe2 highly distorted mixed-anion building units leading to a large Second-Harmonig generation response. Liu, K.W et al. s.l. : Chemistry of materials, 2015, Vol. 27.
Authors : Maria Bouri, Ulrich Aschauer
Affiliations : Department of Chemistry and Biochemistry, University of Bern, Switzerland
Resume : Recently, water splitting using solar radiation as energy source to produce hydrogen fuel has attracted much attention. Overall water splitting consists of two reactions, the hydrogen (HER) and oxygen evolution reaction (OER). It is known that the latter reaction requires high overpotentials and the discovery and design of catalyst materials that overcome these high overpotentials is thus required. Oxides with the perovskite structure were reported to have good catalytic properties. However, their wide band gap limits their activity to the UV part of the solar spectrum. Substitution of oxygen with the less electronegative nitrogen narrows the band gap making oxynitrides suitable for photocatalysis. Layered perovskites were shown to have better photocatalytical activity than the non-layered ones. However, there are no studies on the OER activity of layered oxynitrides with the perovskite structure. In the present work, we investigate the electronic properties of the oxynitride Sr2TaO3N and its surfaces by density functional theory (DFT). Moreover, we investigate the OER activity on these surfaces by calculating the OER free energy changes and the overpotentials required on each surface to predict the most active surface and reaction site. We find that the (001) TaON-terminated surface is more relevant for photocatalysis due to its electronic features that may lead to suppression of electron-hole recombination and its low OER overpotentials.
INNOVATIVE SYNTHESIS 1 : Songhak Yoon
Authors : Simon Clarke
Affiliations : Department of Chemistry, University of Oxford, UK
Resume : Oxide chalcogenides and oxide pnictides have become of increasing interest following the discovery of the iron-based pnictide and chalcogenide superconductors. In this presentation the synthesis, crystal structures and physical properties of a series of layered oxide chalcogenides and oxide arsenides will be described and the changes in magnetic ordering and other physical properties will be described as functions of temperature and composition, and related to changes in crystal structure. In particular, the control that can be exerted over the structural and physical properties in the series A2MO2B2Ch2 (A = electropositive metal, M = transition metal, B = coinage metal, Ch = chalcogenide) will be described. This includes tuning the oxidation state of the transition metal using soft chemical approaches to changing the coinage metal content, and tuning the spin state of the transition metal by tuning the ligand field via chemical substitution on various crystallographic sites.
Authors : Steven Angel 1, Julian Neises 1, Maik Dreyer 2, Klaus Friedel-Ortega 2, Malte Behrens 2, Christof Schulz 1, Hartmut Wiggers 1
Affiliations : 1 IVG, Institute for Combustion and Gas Dynamics - Reactive Fluids and CENIDE, University of Duisburg-Essen, Germany, 2 Faculty of Chemistry, University of Duisburg-Essen, Germany
Resume : Perovskite nanomaterials composed of LaMO3 (M = Fe, Co) are of current interest for environmental catalysis applications, e.g., oxidation of CO and CH4, and for catalytic energy conversion reactions such as water splitting. The synthesis of such compounds is commonly done in time and energy consuming batch processes. Alternatively, spray-flame synthesis (SFS) allows the formation of functional perovskite nanoparticles in a single step. Cost-efficient production requires the utilization of cheap and abundant precursors such as metal nitrates. However, the use of metal nitrates in SFS is often associated with the formation of particles non-homogeneous in size. Furthermore, the different melting/decomposition mechanisms and their different solubility in solvents such as ethanol cause the formation of undesired phases, e.g., La2CoO4, La2O3 and Co3O4, which are often obtained in parallel to the main perovskite phase. In order to improve the perovskite homogeneity in size and composition, mixtures containing the metal nitrate precursors and two different solvents, ethanol and 2-ethylhexanoic acid (2-EHA), were employed in this study. The incorporation of 2-EHA has been previously investigated and a positive effect toward narrow particle-size distributions has been observed. It is suggested that the addition of 2-EHA leads to the formation of micro-explosions in the droplets through superheating of ethanol and the formation of volatile metal carboxylates, which is investigated in this study. LaCoO3 and LaFeO3 nanoparticles were synthesized from solutions of the respective nitrates in ethanol/2-EHA. To understand the effect of 2-EHA on the product properties, temperature-dependent liquid-phase ATR-FTIR studies were performed. It was found that an esterification of 2-EHA with ethanol occurred forming ethyl-2-ethylhexanoate (verified by GC/MS). We assume that the metal nitrates act as catalysts as reported for similar reactions. The nanoparticle products were characterized using XRD, XPS, TEM, SAXS, and Mößbauer spectroscopy. The measurements confirm that the incorporation of 2-EHA in the solution was effective for obtaining homogeneous, single-phase, and high-surface-area products (LaCoO3: dp = 11 nm, SSA > 90 m2/g, LaFeO3: dp = 15 nm, SSA > 88 m2/g). The LaFeO3 and LaCoO3 perovskites were evaluated for the catalytic oxidation of carbon monoxide, reaching temperatures lower than 206°C for the 50% CO conversion.
Authors : Shintaro Ida, Takumi Ideta, Keisuke Awaya, Michio Koinuma
Affiliations : Department of Chemistry, Kumamoto University, Japan
Resume : Calcium tantalum oxynitride (Ca2Ta3O9N) nanosheet was prepared by exfoliating a layered perovskite oxynitride, Na2Ca2Ta3O9N, via proton exchange and two-step intercalation of ethylamine (EA) and tetrabutylammonium (TBA) ions. Intercalation of EA is essential for preparing nanosheets since TBA+ ions (the exfoliation reagent) are not intercalated into the protonated form without EA intercalation. Monolayer nanosheets could be prepared by the above processes, although some bilayer or trilayer nanosheets were also produced. The Ca2Ta3O9N nanosheets exhibited photocatalytic activity for H2 evolution from water under visible light irradiation in the presence of sacrificial agent. In contrast, NaCa2Ta3O9N exhibited lower photocatalytic activity compared with the nanosheet. The improved photocatalytic activity originates from their large surface area.
POSTER SESSION : .
Authors : Xin Zhang, Feng Wang
Affiliations : Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong SAR
Resume : Photon upconversion featuring higher photon output than pump wavelength, has been well developed in lanthanide activator (e.g. Er3+, Ho3+ and Tm3+) over the past decade. However, the lack of transition-metal activated emission has restrictions on applications in some aspect. Herein, we report a strategy to realize manganese (II) upconversion in a CaZnOS semiconductor through co-doping of Er3+. Powder samples were obtained by simply mixing raw materials and calcination under high temperature. Phase purity was checked by powder X-ray diffraction. Photoluminescence emission (PL)/excitation (PLE), upconversion luminescence spectra and upconversion lifetime have been systematically investigated to reveal the underlying mechanism Mn2+ upconverison. By finely adjusting doping concentration of both Mn2+ and Er3+, we finally obtain comparable broad upconverison emission with maximum at 613 nm, arising from Mn2+, 4T1?6A1 optical transition. The Er3+ to Mn2+ energy transfer has been confirmed by the decreased lifetime in the emission of Er3+ at 562 nm. In addition, we are committed to enhance Mn2+ emission by improving energy transfer efficiency from Er3+ to Mn2+ and trying to tune the upconversion emission wavelength by manipulating host lattice. Despite above, the Er3+ and Mn2+ co-doping approach provides a good reference for designing and fabricating novel upconversion luminescent materials.
Authors : Diana Chaykina 1, Tom de Krom 2, Giorgio Colombi 1, Thomas Prokscha 3, Steffen Cornelius 1, Stephan Eijt 2, Bernard Dam 1
Affiliations : 1 Department of Chemical Engineering, Delft University of Technology, The Netherlands, 2 Department of Radiation Science and Technology, Delft University of Technology, The Netherlands, 3 Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Switzerland
Resume : Rare-earth metal oxyhydrides, including yttrium oxyhydride (YOxHy), are promising mixed anion materials in view of their photochromic properties and hydride ion mobility. YOxHy thin-films are synthesized by reactive magnetron sputtering where the anion ratio is tuned by the deposition conditions. The present work focuses on elucidating the nature of hydrogen in YOxHy by muon spin rotation (μSR), employing the muon as a hydrogen-mimicking probe under zero field (ZF) and transverse magnetic field (TF) to explain structural and electronic properties respectively. The ZF data reveals the presence of μ+–H- or negative muonium (Mu-) –H- pairs via their entangled two-spin interaction. All extracted μ+-H- distances were substantially larger than the H2 molecular distance yet significantly smaller than the H?H distances in the crystal lattices of both YH2 and YOxHy. YH2 shows the presence of one type of μ+-H- pair, while the YOxHy samples indicate a spread in μ+-H- distances, possibly reflecting partial occupation of H- at octahedral sites and not only tetrahedral sites. The TF analysis shows that neutral muonium (Mu0) was formed in the semiconducting YOxHy films but not in the metallic YH2. In-situ UV illumination of the photochromic YOxHy films reduces the formation of Mu0, plausibly related to the generation of charge carriers upon photodarkening. These carriers can interact with Mu0 to form Mu-, or Mu0 itself can be excited by the light exposure and release its electron forming μ+.
Authors : G. Colombi 1, S. Cornelius 1, A. Longo 2, D. Chaykina 1, B. Dam 1
Affiliations : 1 Department of Chemical Engineering, Delft University of Technology, The Netherlands, 2 Dutch-Belgian Beamline, ESRF, France
Resume : Rare Earth (RE) metal oxy-hydrides are promising multi anion materials which show photochromic properties under ambient conditions. Their transmittance decreases reversibly by exposure to sunlight and this effect may extend from the UV up to the mid-IR . Therefore these materials are not only suitable for visible light-modulation but they can also act as a barrier to solar thermal radiation. In our latest work we show that it is possible to synthesize two different kinds of RE-based line compounds by reactive magnetron sputtering: the hydroxides and oxyhydrides . Only the oxyhydrides are photochromic and this study attempts - in two steps - to shed insight into the origin of such difference. First, we complement the picture with structural analysis (XRD & EXAFS). In doing so, we also establish that the oxygen atoms occupy tetrahedral sites in the cubic lattice (Ia-3) of the oxyhydrides; supporting thus the anion-disordered model proposed in . Second, the compositional and structural information is used to compute by DFT the band structures of the two types of materials. The comparison of the P-DOS suggests that hydrogen plays a distinctly different role in defining the electronic and optical properties of the two line compounds. References:  F. Nafezarefi et al. Appl. Phys. Lett. 111 (2017) 103903  S. Cornelius et al., J. Phys. Chem. Lett. (2019) submitted
Authors : A. Bousquet, S. Ibrahim, F. Zoubian, P. Bonnet, C. Taviot-Guého, J. Cellier, E. Tomasella, M. Sarakha
Affiliations : Institut de Chimie de Clermont-Ferrand (ICCF), Université Clermont, France
Resume : Mixed anion materials are highly known to present tunable properties thanks to anion substitution. Among the available synthesis methods, reactive sputtering is a particularly versatile technique to deposit thin films with a controlled composition by only tuning the injected gas mixture. Moreover, as a gas/solid synthesis technique, it is known to be environment-friendly method, widely used in industry. In the present study, we focus on deposition of tantalum oxynitrures (by sputtering a tantalum target in Ar/O2/N2 atmosphere) and bismuth oxyfluorides (from bismuth target in Ar/O2/CF4 atmosphere) as photocatalysts. RBS shown films with composition varying from tantalum/bismuth oxide to tantalum nitride or bismuth fluoride are obtained. Nature of these deposits was deeply investigated by XPS, FTIR, and XRD, associated to Pair Distribution Function technique. Films can be considered as randomly mixed compounds at very short scale (< few nm). Optical properties, followed by UV-visible spectroscopy and spectroscopic ellipsometry, are explained by the contribution of these different compounds leading to varisou metallic, semiconductor or insulator global behavior of the layer. Moreover, fine bandgap engineering is achieved for tantalum oxynitrides with values ranging from 1.7 to 2.7 eV with N to O substitution and for oxyfluoride (4-4.8 eV). These light absorption properties were then link to difference in photocatalytic activities.
Authors : Yoshihiro Tsujimoto 1, Yu Su 1, Kotaro Fujii 2, Masatomo Yashima 2, Kazunari Yamaura 1
Affiliations : 1 National Institute for Materials Science, Japan 2 Tokyo Institute of Technology, Japan
Resume : Anion-lattice engineering for Cr4+-rich perovskite materials via topochemical routes has an unexplored area because (i) the tetravalent chromium cation prefers a tetrahedral coordination to an octahedral coordination and (ii) the ionic radius is too small in size to be incorporated into perovskite structures. However, utilizing high pressure synthesis can stabilize high-valent chromium perovskite oxides, which will be promising precursors for low-temperature reactions. We report the fluorination of SrCrO3 by PVDF for the first time, in which a superstructured oxide SrCrO2.8 was formed as an intermediate phase. SrCrO2.8 had not been obtained as a single phase, but we could successfully synthesize this phase as a single phase for the first time using carbothermal reduction technique.
Authors : Wei Sun 1, Pengyu Cheng 1, Yifei Fang 1,2, Jinyan Ning 1, Zhihan Wang 1, Fei Chen 1, Yingying Chen 1, Jincang Zhang 1*
Affiliations : 1 Materials Genome Institute, Shanghai University, China, 2 Department of Physics, Fudan University, China
Resume : The perovskite RMnO3 (R=rare-earth) exhibits a rich variety of physical properties depending on the type of rare-earth. When R site is doped alkaline earth mental elements, the compound becomes ferromagnetic through the double-exchange interaction. In this present, we have studied the crystal structure and magnetic properties for co-doping Y0.3Lu0.7MnO3 single crystalline by performing X-ray diffraction and magnetization measurements, respectively. The sample of Y0.3Lu0.7MnO3 single crystal with pure phase was grown by the floating-zone method. Experiments shows the characteristics of re-entrant spin glass behavior at low temperatures in the c axis, but no such behavior in the a axis for Y0.3Lu0.7MnO3 single crystal. The refinement results of X-ray diffraction pattern reveal that pure single-phase sample exhibits hexagonal structure with P63cm space group. Upon cooling, it undergoes multiple magnetic phase transitions, i.e., antiferromagnetic, weak ferromagnetic, and spin glass transitions along its c axis. And it only undergoes antiferromagnetic transition along the a axis over the whole measured temperature range, indicating that 70% Lu doping leads to the change of magnetic anisotropy. The magnetic properties show that re-entrant spin glass behaviour in Y0.3Lu0.7MnO3 single crystal mainly results from the magnetic frustration and the disorder coming from Lu dopant. In addition, the magnetic frustration is correlated with the competition between the antiferromagnetic and weak ferromagnetic interactions. The present study would be helpful for people to understand the physical behavior in co-doped R1-xAxMnO3 manganite compounds.
Authors : Chengchao Zhong, Daichi Kato, Kotaro Fujii, Masatomo Yashima, Yasuhiro Fujii, Akitoshi Koreeda, Ryu Abe, Hiroshi Kageyama
Affiliations : 1 Department of Energy and Hydrocarbon Chemistry Kyoto University, Japan 2 Department of Chemistry, Tokyo Institute of Technology, Japan 3 Department of Physical Sciences, Ritsumeikan University, Japan
Resume : Sillen-Aurivillius type structure consists of [An-1BnO3n-1] layer (n = the number of perovskite blocks) sandwiched by double [Bi2O2] layers and single halide [X] layer along the c axis. Several interesting chemical and physical properties were found in this series of compounds. For example, n = 1 Bi4NbO8X (X = Cl, Br) is a novel photocatalyst for water splitting, as well as a potential Pb-free ferroelectric material. Furthermore, Sillen?Aurivillius type structure is designable by changing the block of layers. How these properties differ by changing the layer, such as inserting one perovskite block to form Bi3Pb2Nb2O11Cl (n = 2), is also worthwhile studying. In order to obtain further insight into these properties, such as carrier dynamics for photocatalyst, the measurements using single crystals are desirable. However, details about single crystal growth of Sillen?Aurivillius compounds have not been reported yet. In this work, single crystals of Bi4NbO8X were successfully obtained after examining and optimizing synthetic conditions such as heating temperature, keeping time and cooling rate. The key to growing the single crystal of multi-anion compounds was finding a proper condition that can suppress the volatilization of different anionic species. By using this knowledge, the single crystal of Bi3Pb2Nb2O11Cl was successfully obtained as well. References:  Fujito, H., et al. J. Am. Chem. Soc. 2016, 138, 2082-2085.  Kusainova, A. M., et al. Chem. Mater. 2001, 13, 4731-4737.
Authors : Steven Angel 1, Juan David Tapia 2, Jaime Gallego 2, Christof Schulz 1, Hartmut Wiggers 1
Affiliations : 1 Institute for Combustion and Gas Dynamics, University of Duisburg-Essen, Germany, 2 Institute of Chemistry, University of Antioquia, Republic of Colombia
Resume : LaMnO3 perovskite is currently being investigated as a potential and inexpensive alternative to noble metals (e.g. Pd or Pt) for catalytic reactions. A specific focus is on decontamination and purification reactions such as the preferential oxidation (PROX) of CO in excess hydrogen. In order to synthesize suitable, high surface area LaMnO3 nanomaterials, the spray-flame synthesis (SFS) technique was used as it provides a continuous, single step and cost-efficient production way. Concerning the formation of a functional and active catalyst, the main challenges of this technique include avoiding multimodal and broad particle size distributions, the formation of secondary non-active phases such as La2O3, and low reducibility. Metal nitrates as cost-effective precursors were dissolved in solutions containing ethanol or mixtures of ethanol and 2-ethylhexanoic acid (2-EHA), whereas the latter combination is known to support the formation of extremely fine-grained nanomaterials. A specific interest was in the thermal and chemical stability of the as-prepared solutions. Therefore, liquid phase temperature-dependant ATR-FTIR and UV-VIS studies were performed. While the ethanol solutions didn?t show any changes in chemical composition, esterification between ethanol and 2-EHA was observed most likely catalyzed by manganese. Moreover, the oxidation of Mn2+ to Mn3+ and Mn4+ was found above 40°C. However, these solutions showed an excellent stability and enabled the formation of small particles with a unimodal and narrow size distribution (dp = 7.3 nm). Traces of an oxygen-rich LaMnO3 phase were identified on the particles’ surface containing a Mn4+/Mn3+ ratio of 0.5 (XPS). The samples were evaluated for CO-PROX, obtaining at 220°C a conversion of CO of 85% while keeping the conversion of hydrogen below 10%.
Authors : Dong-Hyeon Seo, Chung-Hyo Lee
Affiliations : Department of Advanced Materials Science and Engineering, Mokpo National University, Republic of Korea
Resume : Half-metallic ferromagnets (HMFs) have the potential to apply in many fields related to electronic transport and spintronics and are worth further investigation. HMFs exhibit a semiconductor behavior in one spin band at the Fermi level. Among some kinds of HMFs, Co-based Heusler alloys are of particular interest due to comparatively high Curie temperatures. Mechanical alloying (MA) has been applied to produce nanocrystalline Co2MnSi Heusler alloys. A two-phase mixture of amorphous phase and remaining Mn were obtained after 5 hours of MA without any evidence for the formation of Co2MnSi alloys. The saturation magnetization of MA powders decreased with MA time due to the magnetic dilution by alloying with nonmagnetic Mn and Si elements to 48 emu/g after 5 hours of MA. On the other hand, a Co2MnSi single phase was obtained by MA after 3 hours and subsequently heat treated up to 650°C. X-ray diffraction result showed that the average grain size of Co2MnSi Heusler alloys prepared by MA for 5 hours and heat treatment to be in the range of 85 nm. The saturation magnetization of Co2MnSi Heusler alloys prepared by MA and heat treatment reached a maximum value of 112 emu/g for 5 hours MA sample. It was also observed that the coercivity of 5 hours MA sample annealed at 650°C was fairly low value of 27 Oe.
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INNOVATIVE SYNTHESIS 2 : Houria Kabbour
Authors : Joke Hadermann
Affiliations : Electron microscopy for Materials research (EMAT), University of Antwerp, Belgium
Resume : Several well-known perovskite based materials can be considered as modular compounds, i.e. consisting of blocks of perovskite and blocks of other fragments or even of other basic structure types. Examples are the Ruddlesden-Popper type compounds which consist of stacked perovskite blocks and rock salt slabs, and the Aurivillius and Dion-Jacobson type phases which respectively contain a fluorite type slab and single cation layers in between perovskite blocks. In this lecture, we will show several alternative perovskite based modular compounds, effectively synthesized and characterized, containing a range of different structural fragments in between the perovskite blocks, from including anatase and Sillen blocks to interfaces originating from controlled shearing between the perovskite blocks themselves. All compounds were powder samples made by solid state chemistry and characterized using advanced transmission electron microscopy, combined with, when possible, X-ray (synchrotron) and neutron powder diffraction.
Authors : Kiyofumi Katagiri 1, Yuki Hayashi 1, Risa Yoshiyuki 1, Kei Inumaru 1, Tomoki Uchiyama 2, Noriyuki Nagata 2, Yoshiharu Uchimoto 2, Akinobu Miyoshi 3, and Kazuhiko Maeda 3
Affiliations : 1 Department of Applied Chemistry, Hiroshima University, Japan, 2 Graduate School of Human and Environmental Studies, Kyoto University, Japan, 3 Department of Chemistry, Tokyo Institute of Technology, Japan
Resume : A solid solution of GaN and ZnO (GaN:ZnO) is promising as a photocatalyst for visible light-driven overall water splitting to produce H2. However, several obstacles still exist in the conventional preparation procedure of GaN:ZnO. For example, the atomic distributions of Zn and Ga are non-uniform in GaN:ZnO when a mixture of the metal oxides, i.e., Ga2O3 and ZnO, is used as a precursor. In addition, GaN:ZnO is generally prepared under harmful NH3 flow for long durations at high temperatures. In this work, we have demonstrated a facile preparation of GaN:ZnO that addresses the obstacles associated with their conventional preparation route. A layered double hydroxide (LDH) containing Zn2+ and Ga3+ was employed to increase the uniformity of the atomic distributions of Zn and Ga in GaN:ZnO. We employed urea as a nitriding agent instead of gaseous NH3 to increase the safety of the reaction. Through the optimization of reaction conditions such as heat-treatment temperature and content of urea, single-phase GaN:ZnO was successfully obtained. In addition, the nitridation mechanism using urea was investigated in detail. NH3 released from the thermal decomposition of urea did not directly nitride the LDH precursor. X-ray absorption and infrared spectroscopies revealed that ZnCN2-like intermediate species were generated at the middle temperature range and Ga-N bonds formed at high temperature along with dissociation of CO and CO2.
Authors : Kévin Guy 1,2,4, Stéphane Cordier 1, Franck Tessier 1, Fabien Grasset 2,3, Helena Kaper 4, Tetsuo Uchikoshi 2,3, David Lechevalier 2, Caroline Tardivat 4
Affiliations : 1 Univ. Rennes, CNRS, Institut des Sciences Chimiques de Rennes, France, 2 CNRS-Saint-Gobain-NIMS, NIMS, Japan, 3 Research Center for Functional Materials, NIMS, Japan, 4 LSFC, CNRS-Saint-Gobain Recherche Provence, France
Resume : Transition metal nitrides (TMN) form a class of materials with unique physical and chemical properties, which give them a wide variety of applications (magnetism, pigments, photocatalysis ...). Among the TMNs, molybdenum nitrides form a family of compounds with remarkable mechanical and physical properties. They are mainly used for high performance magnets, superconductors or as catalysts for a wide range of reactions . This presentation will focus on the synthesis of molybdenum nitrides and their characterization. Novel synthetic approaches, in particular using transition metal clusters, will be discussed since the nature of the starting material is of prime importance to stabilize specific stoichiometries . Some results will be shown about the targeted application in heterogeneous catalysis (Water-Gas Shift Reaction: CO + H2O -> CO2 + H2)  The use of a nanoscale precursor such as (TBA)2Mo6Br14  makes it possible to obtain different molybdenum nitrides (Mo2N, Mo5N6) by thermal reaction under ammonia at relatively low temperatures. The impact of this new synthetic route has been characterized in particular by SEM, TEM and specific surface measurements. References:  Hargreaves J.S.J. Coordination Chemistry Reviews 257 (2013), 2015-2031.  Marchand R., Tessier F., DiSalvo F.J. J. Mater. Chem. 9 (1999), 297-304.  K. Guy, F. Tessier, S. Cordier, H. Kaper, C. Tardivat, F. Grasset, T. Uchikoshi, D. Lechevalier, Chem. Mater. (2019), submitted.  Kirakci K., Cordier S., Perrin C. Z. Anorg. Allg. Chem. 631 (2005), 411-416.
Authors : Cora Bubeck 1, Marc Widenmeyer 1, Alexandra T. De Denko 2, Gunther Richter 3, Mauro Coduri 4, Eduardo Salas Colera 4, Eberhard Goering 5, Songhak Yoon 1,6, Frank E. Osterloh 2, Anke Weidenkaff 1,6,7
Affiliations : 1 Institute for Materials Science, University of Stuttgart, Germany 2 Department of Chemistry, University of California, USA, 3 Central Scientific Facility Materials, Max Planck Institute for Intelligent Systems, Germany, 4 European Synchrotron Radiation Facility (ESRF), France, 5 Modern Magnetic Systems, Max-Planck-Institute for Intelligent Systems, Germany, 6 Fraunhofer IWKS, Germany, 7 Department of Materials and Earth Sciences, Technische Universität Darmstadt, Germany
Resume : Many perovskite-type oxynitrides AB(O,N)3 are well-known for solar water splitting and other visible light-driven applications.[1?3] In literature usually d0 or d10 as electronic configurations[3,4] for the B-site cation in AB(O,N)3 (e.g. d0 in LaTa(V)ON2) are reported. Hence, producing new perovskite-type oxynitrides containing B-site cations with d1 electron can offer new possibilities of applicability due to a modified electronic band structure. In general, to synthesize perovskite-type oxynitrides, crystalline oxide precursors are ammonolyzed at high temperatures. In these cases a topotactic reaction[1,3] leads to Ta5+ in LaTa(V)ON2. To break down this strong topotactic relation and to produce other oxidation states than Ta5+ in LaTa(O,N)3, a precursor-controlled ammonolysis can be used. This procedure allows the formation of Ta4+ leading to LaTa(IV)O2N due to microstructural adjustment of the oxide precursor and the right ammonia concentration. Further application of this synthetic approach in other chemical systems such as La1-xYxTa(O,N)3 leads to Ta4+ (La1-xYxTa(IV)O2N) as well. References:  S. G. Ebbinghaus, H. P. Abicht, R. Dronskowski, T. Müller, A. Reller, A. Weidenkaff, Prog. Solid State Chem. 2009, 37, 173?205.  C. Bubeck, M. Widenmeyer, G. Richter, M. Coduri, S. Yoon, A. Weidenkaff, 2019, submitted.  T. Yajima, F. Takeiri, K. Aidzu, H. Akamatsu, K. Fujita, W. Yoshimune, M. Ohkura, S. Lei, V. Gopalan, K. Tanaka, et al., Nat. Chem. 2015, 7, 1017?1023.  M. Yang, J. Oró-Solé, J. A. Rodgers, A. B. Jorge, A. Fuertes, J. P. Attfield, Nat. Chem. 2011, 3, 47?52.  H. Kageyama, K. Hayashi, K. Maeda, J. P. Attfield, Z. Hiroi, J. M. Rondinelli, K. R. Poeppelmeier, Nat. Commun. 2018, 9.  C. Bubeck, M. Widenmeyer, A. De Denko, G. Richter, M. Coduri, E. Salas Colera, A. Senyshyn, E. Goering, S. Yoon, F. Osterloh, et al., 2019, in preparation.
Authors : Sung Haeng Cho, Sooji Nam, Su-Jae Lee
Affiliations : Electronics Telecommunications Research Institute (ETRI), Republic of Korea
Resume : We report a development of new p-type metal oxide semiconductor thin-film transistor with high Hall and field-effect hole mobility fabricated in solution process. Over the last few decades, metal oxide semiconductors have attracted huge attention as large-area electronic devices by virtue of high electrical and optical performances such as transparency, large electron mobility, good uniformity and low-temperature processability and their mass production has now been successfully realized in the active matrix backplane of flat-panel or flexible display. Few p-type metal oxide semiconductors with high performance, however, have been reported compared with n-type metal oxide semiconductors such as InGaZnO, InZnSnO, etc. This is mostly ascribed as the localization of valence band maximum which mainly consists of oxygen p orbitals. To enhance the dispersion of valence band, it has been theoretically proposed that the filled diffuse metal d or s orbital to hybridize with oxygen 2p orbital can be utilized and indeed it was experimentally demonstrated that Sn 5s orbital and Cu 3d orbital played such a role in SnO and CuO, respectively. But, SnO phase is very vulnerable to disproportion reaction to metallic Sn and SnO2 which behaves as an n-type semiconductor so that the process window to realize it in electron devices was very narrow and the electrical performance in the devices such as thin-film transistor was very limited, e.g low on/off ratio. Inspired by the theoretical work of high throughput materials screening performed by the first principles calculation, we fabricated potassium-doped SnO thin-film with solution process and low-temperature annealing less than 400 oC. We found that the oxidation state of Sn in thin-film changed from +4 state (SnO2 phase) to +2 state (SnO phase) depending on the content of alkali metal ions from x-ray photoelectron spectroscopy (XPS). Furthermore, Hall-effect measurement indicated the type conversion of the majority carrier from n-type to p-type as the content of alkali metal ion increases, in consistence with XPS results. The high hall mobility of 51 cm2/Vs was obtained at the optimal potassium-doped SnO thin film and we successfully fabricated TFTs with a field-effect hole mobility over 7 cm2/Vs. We hope that this work will contribute to open a new era for transparent large area electronics based on oxide semiconductors with high functionalities such as complementary logic circuit.
ELECTRONIC AND MAGNETIC PROPERTIES : Hiroshi Kageyama
Authors : Evgeny V. Antipov
Affiliations : Department of Electrochemistry, Lomonosov Moscow State University, Russia
Resume : The ever-growing demand for portable energy in various fields puts forward new challenges to rechargeable battery technologies in improving specific energy and power, life and safety. The battery performance is critically governed by the properties of the cathode material. Fluoride-phosphates of transition metals with AxMPO4F (A = Li, Na, K; M = V, Fe, Co) formula take several advantages over existing oxide cathode materials: a substantial increase of operating voltages due to the inductive effect and much faster kinetics . A distinctive structural feature of these materials is a presence of dangling oxygen atoms (bonded to P and alkaline cations, but not included into the octahedral coordination of transition metals). These oxygen atoms can determine the mechanism of the structure transformation during charging and even trigger the undesirable cation intermixing. Different activities of the alkali positions surrounded by a distinct number of the dangling oxygen atom can explain the striking difference between desodiation mechanisms in Na-ion and Li-ion cells of a layered Na2FePO4F cathode material . Recently we proposed a novel series of vanadium-based AVPO4F (A = Li, Na, K, Rb) cathode materials crystallizing in a KTiOPO4 (KTP)-type structure. The KTP-type “VPO4F” framework featured outstanding rate capability and capacity retention especially in Li cells: the material maintained more than 75% of the initial specific capacity at the 40C rate with an average potential of 4.0 V vs. Li/Li+ . Another quality of this framework is supporting reversible Na+, K+ and even Rb+ ions de/insertion sustaining the host structure. The electrochemical performance and ion transport properties were different for various alkali ions. The ion diffusion coefficients obtained by PITT were the lowest for Li+ (10-12 – 10-14 cm2/s) and the highest for K+ (10-11 – 10-12cm2/s), with the latter anticipating high-power applications of KVPO4F in K-ion batteries . Our current activities on transition metal fluoride-phosphate based cathode materials for metal-ion batteries will be reported with a particular focus on the interrelation between crystal structure peculiarities and electrochemical properties. This work was supported by the Russian Science Foundation (grant No. 17-73-30006). References:  E.V. Antipov et al. IUCrJ 2 (2015) 85-94.  I.V. Tereshchenko et al. JACS 140 (2018) 3994-4003.  S.S. Fedotov et al. Chem. Mater., 28 (2016) 411-415.  V.A. Nikitina et al. JES, 164 (2017) A6373-A6380.
Authors : Jaye K Harada 1, Po-Hsiu Chien 2, Haoyu Liu 2, Ching-Hwa A Chen 3, Nenian Charles 1, Michael Holland 3, Yan-Yan Hu 2,4, Kenneth R Poeppelmeier 1,3, James M Rondinelli 1
Affiliations : 1 Department of Materials Science and Engineering, Northwestern University, Evanston, USA, 2 Department of Chemistry and Biochemistry, Florida State University, USA, 3 Department of Chemistry, Northwestern University, USA, 4 Center of Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, USA
Resume : The ordered oxyfluoride KNaNbOF5 exhibits a reversible, temperature-dependent phase transition from a polar room temperature phase to a centrosymmetric high temperature structure. Although a single critical ordering temperature is observed, crystallographic mode analyses shows that two lattice modes are required to produce the structure of the low-symmetry phase; these facts together suggest an improper character requiring further investigation. We assess the character of this phase transition using a combination of computational and experimental techniques. We use density functional theory calculations and phenomenological Landau theory to determine the relevance of permitted trilinear multimode interactions on the stability of the observed phases and the suppression of potential intermediate phases. We also use temperature-resolved 19F NMR and powder x-ray diffraction to further search for intermediate phases. Based on the nature of the phase transition, we discuss the potential for switchable ferroelectricity.
Authors : Bastien Leclercq, Sarah Nicoud, Olivier Mentré, Houria Kabbour
Affiliations : Unité de Catalyse et de Chimie du Solide, Université de Lille, France
Resume : Mixed anions systems offer great opportunities to discover new materials with original chemical and physical features. While 1D oxides are actively explored due to their unique properties, 1D mixed anion phases are less prospected. One example is the oxy-chalcogenide Ba3V2O3S4 formed by infinite chains of V3+S6 sharing faces and separated by Ba2+ ions and V5+O3S mixed anion entities. This phase is a Mott insulator with quasi-1D S=1 frustrated spin chains . The (VS3) chains may be replaced by (CrS3) chains . Note that these phases represent the only oxysulfide cases within the broad series of isotypic chalcogenides A3(M1-xS3)(XS4) (A= rare earth ; M= Fe, Cu, … ; X= Si, Ge …).  The chains provide tunable low dimensional magnetic/electronic properties. A rational modification of the chain in the present work led to several phases in the solid solution Ba3(V,Cr)2O3S4 , in particular the Cr3+ chains compound was further investigated and represent a quasi-1D S=3/2 Heisenberg chains. In the larger family, we present the design of new phases based on Cu/Fe solid solutions starting with La3CuSiS7 in which Cu is in a triangular coordination Cu+S3, with the aim to induce ordering. The experimental characterizations accompanied by DFT study will be presented. References:  E. J. Hopkins et al. Chem. Eur. J. 21, 2015, 7938-7943  Kim, J. et al. J. Mag. Mag. Mat. 2017, 435,126-135  Gulay, L. D. et al. J. Alloys Compd. 2006, 425 (1-2), 159-163
Authors : Takao Mori, Naoki Sato, Fainan Failamani, Hyoungwon Son
Affiliations : 1 National Institute for Materials Science (NIMS), Japan, 2 University of Tsukuba, Japan
Resume : Thermoelectrics is a promising field challenging to reach wide-scale application in waste heat power conversion, and now especially with a focus on energy harvesting to power IoT sensors, etc. . The strategy of utilizing mixed anions has been well used in thermoelectrics research, mainly as a way to tune the carrier concentration, which is typically important for optimization of power factor. As a different aspect, previously, additions of C and N to higher borides were found to function as bridging sites resulting in new network structures, i.e. novel rare earth borocarbonitrides, which exhibited anomalous n-type . I will report on a couple other strategies we have taken. Rare earth skutterudites, such as RECoSb3 are known as high figure of merit ZT materials, where the rare earth atoms are said to function as rattlers to scatter acoustic phonons. Conversely, rare earth-free skutterudites, CoSb3-based materials have relatively high thermal conductivity and significantly lower ZT. As a byproduct of a mixed anion strategy of co-doping Te and Si, a secondary phase Sb2Te with low melting temperature was purposely precipitated in n-type CoSb2.75Si0.075Te0.175, and by simple annealing, a distribution of nano-micropores was successfully created, leading to effective phonon scattering and a 100% enhancement of ZT to ~1.6 . Recently we have used a similar approach, based on mixed anions, to enhance the ZT of p-type rare earth-free skutterudites also, and this will be reported in detail. As another broad mixed anion approach, compositing insulating oxides and metallic nitrides has led to significant ZT enhancement. Finally, at the atomic level, mixed anions may be a way to tune the anharmonicity of materials, and we have carried out phononic calculations which indicate that ultra-low thermal conductivity can be attained. References:  T. Mori and S. Priya, MRS Bulletin, 43, 176 (2018), I. Petsagkourakis, et al., Sci. Tech. Adv. Mater., 19, 836 (2018).  T. Mori, et al, Dalton Trans., 43, 15048 (2014), Handbook Phys. Chem. Rare-earths, Vol. 38, (2008) 105-173.  A. U. Khan, et al., Nano Energy, 31, 152 (2017).
Authors : Marc Widenmeyer 1, Songhak Yoon 1,2, Joachim Häcker 1,3, Anke Weidenkaff 1,2,4
Affiliations : 1 Institute for Materials Science, University of Stuttgart, Germany, 2 Fraunhofer IWKS, Germany, 3 Institute of Engineering Thermodynamics, German Aerospace Center, Germany, 4 Department of Materials and Earth Sciences, Technische Universität Darmstadt, Germany
Resume : The double-anionic substitution of O2– for N3– and F- in perovskite-type oxides leading to formation of perovskite-type oxynitridefluorides AB(O,N,F)3[1,2] is less explored in comparison to cationic modification. In the case of SrTi(O,N,F)3 a clear reduction of the optical band gap by ca. 0.7 eV compared to SrTiO3 was observed, while partial substitution of nitride and/or fluoride for oxide does not change its optical properties dramatically for BaTi(O,N,F)3 even though the incorporated N content is higher. In the case of BaTiO3 the double-anionic substitution seems to lead to an enhanced formation of defect states as confirmed by the increase of the Kubelka-Munk-curve at lower energies than the band gap. In addition, ferromagnetic behavior is induced by a synergetic effect of surface defects and higher Ti3 concentration for BaTi(O,N,F)3. A reason for the difference in the optical properties of SrTi(O,N,F)3 and BaTi(O,N,F)3 is the different oxygen vacancy concentration formed during the precursor synthesis of AB(O,F)3, the strength and nature of the chemical bonding, and the lattice distortion typically described by Goldschmidt’s tolerance factor. To achieve a deeper insight in this interrelations, in particular on the effect of the lattice distortion, further AB(O,N,F)3 materials were synthesized and characterized. In this talk, the importance of controlling the lattice distortions for the formation of double-anionic substituted perovskites will be highlighted. References:  S. Yoon, A. E. Maegli, L. Karvonen, S. K. Matam, A. Shkabko, S. Riegg, T. Großmann, S. G. Ebbinghaus, S. Pokrant, A. Weidenkaff, J. Solid State Chem. 2013, 206, 226.  S. Yoon, K. Son, S. G. Ebbinghaus, M. Widenmeyer, A. Weidenkaff, J. Alloys Comp. 2018, 749, 628.  M. Widenmeyer, J. Häcker, C. Bubeck, S. Yoon, W. Xie, A. Weidenkaff, in preparation.
INNOVATIVE SYNTHESIS 3 : .
Authors : Mathieu Duttine, Nicolas Penin, Etienne Durand, Anthony Chiron and Alain Demourgues
Affiliations : ICMCB-CNRS-University of Bordeaux, France
Resume : The first Ti-based oxy-hydroxy-fluorides with HTB network was prepared by solvothermal route and the original structure has been determined. The optical band gap can be tuned in UV range as a function of the O/F atomic ratio. V or Mo partial substitution contribute to shift the band gap in visible range. The heat-treatment of Fe fluoride trihydrate up to T=350°C under Ar leads to stabilize for the first time, Fe oxy-fluoride with anionic vacancies in the HTB network. The formation of structural units containing 5-fold coordinated Fe atoms in this HTB network leads to a strong reduction of the optical band gap from 4.05 eV in FeF3, 3H2O to 2.05 eV in the Fe oxyfluoride. The annealing under Ar of In fluoride trihydrate at 440°C leads to In oxy-fluoride which adopt a derived fluorite-type structure with O/F ordering. InOF can be considered as transparent conductive oxyfluoride with a band gap energy of 3.7 eV. The reduction under H2 at 700°C of Ce fluoro-carbonate CeFCO3, leads to prepare pure CeOF with O/F ordering and which exhibit a blue-grey coloration. The H2S treatment at T=700°C-800°C of CeIII fluoride, oxyfluoride or fluorocarbonate, allow obtaining Ce fluoro-sulfide CeSF which adopt a 2D network as CeOF, deriving from fluorite-type structure. The band gap strongly vary from UV in CeOF to visible range in CeSF around 2eV. The key features of mixed anions systems will be highlighted from the analysis of reactivity, structure and local environments to tune the band gap.
Authors : C. Le Paven 1, L. Le Gendre 1, M. Haydoura 1, R. Benzerga 1, F. Marlec 1, A. Sharaiha 1, F. Tessier 2, F. Cheviré 2
Affiliations : 1 Univ Rennes, CNRS, IETR UMR 6164, France 2 Univ Rennes, CNRS, ISCR UMR 6226, France
Resume : Materials obtained from the (Sr2Ta2O7)100-x(La2Ti2O7)x solid solution present a layered perovskite structure. We have demonstrated the ferroelectric behavior of this family, called STLTO, on bulk ceramic samples for compositions (x) ranging from 0 to 5. Optimum dielectric performances, at room temperature, were achieved for the composition x = 1.65. The purpose of the work presented here was to produce this STLTO specific composition as a thin film. The combination of an STLTO oxide target with a dioxygen-rich reactive atmosphere during the RF magnetron sputtering deposition leads to Sr-deficient thin films, whatever the percentage of oxygen, shifting composition and structure from the perovskite to the tetragonal tungsten bronze (TTB) type. Films deposited under pure argon show a stoichiometric composition but with a conductive behavior. An alternative synthesis pathway was then to first deposit, under nitrogen-rich atmosphere, stoichiometric oxynitride perovskite films and produce, by thermal annealing under static air, the stoichiometric oxide. Annealing (4 hours) of oxynitride films were performed at temperatures in the range [450 - 1000°C]. For high oxidation temperature [600 - 1000°C], samples show damage with a film peel-off from the substrate. For low oxidation temperature [550-600°C], samples remain intact and display an oxide character but still contain a significant amount of nitrogen; they could be described as intermediate phases as previously reported on powders.
Authors : Aritra Sil 1, Laleh Avazpour 2, Elise Goldfine 3, Qing Ma 4, Wei Huang 1, Binghao Wang 1, Michael J. Bedzyk 3, Julia E. Medvedeva 2, Antonio Facchetti 1,5, Tobin J. Marks 1
Affiliations : 1 Department of Chemistry, Northwestern University, USA, 2 Department of Physics, Missouri University of Science and Technology, USA, 3 Department of Materials Science and Engineering, Northwestern University, USA, 4 Northwestern Synchrotron Research Center, Advanced Photon Source, USA, 5 Flexterra Inc., USA
Resume : Anion-doping of transparent amorphous metal oxide (a-MO) semiconductors can introduce unique opto-electronic materials owing to the chemical tunability and variable structure/charge transport the anion imparts. We report here the effects of fluorine (F) doping in an archetypical MO semiconductor, indium oxide (In-O), by combustion synthesis. Optimized F-doped In-O (F:In-O) thin films are characterized by GIXRD, XRR, AFM, and XPS. The charge transport of the F:In-O films is assessed in TFT architectures revealing that while increased F content (from 0 to 1.57 at%) decreases the mobility, parameters such as the off-current and the Ion/Ioff ratio improve, affording superior switching properties vs. un-doped In-O. These data can be understood through ab initio Molecular Dynamics simulations and EXAFS data, which show that F induces strong local distortions, stabilizes the amorphous state, and creates deep, localized trap states. This is the first report of a combustion-synthesized F:MO semiconductor, elucidating structure-function relationships by both computation and experiment, and opens new avenues to achieve superior opto-electronic properties by MO anion doping.
Authors : Sunghyun Kim and Aron Walsh
Affiliations : Department of Materials, Imperial College London, UK
Resume : Beyond the group oxidation state (N), post-transition metals can adopt a lower (N-2) oxidation state, which is associated with a metal s2 lone electron pair. Solid-state lone pairs, as found in the compounds formed of ions such as In(I), Sn(II), Sb(III), and Te(IV), are linked to the formation of asymmetric local coordination environments and non-centrosymmetric crystal structures . Lone pairs underpin the physical properties of many piezoelectric, pyroelectric and ferroelectric materials. I will discuss progress in the understanding of structure and reactivity of lone pair containing semiconductors. A particular focus is the low open-circuit voltage of kesterite solar cells due to defect-mediated electron–hole recombination . While the oxidation state of Sn is +4 in stoichiometric CZTS, inert lone pair (5s2) formation lowers the oxidation state to +2. The stability of the lone pair suppresses the ionization of certain point defects, inducing charge transition levels deep in the band gap. We find large lattice distortions associated with the lone-pair defect centers due to the difference in ionic radii between Sn(II) and Sn(IV). The combination of a deep trap level and large lattice distortion facilitates efficient non- radiative carrier capture . The results highlight a connection between redox active cations and ‘killer’ defect centres that form giant carrier traps. This effect will be relevant to other emerging energy materials containing lone pair cations. References:  Stereochemistry of post-transition metal oxides: revision of the classical lone pair model. Chem. Soc. Rev. 40, 4455 (2011)  Point defect engineering in thin-film solar cell. Nat. Rev. Mat. 3, 194 (2018)  Lone-pair effect on carrier capture in Cu2ZnSnS4 solar cells. J. Mater. Chem. A 7, 2686 (2019)
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Department of Energy and Hydrocarbon Chemistry - Graduate School of Engineering - Nishikyo-ku, Kyoto, 615-8510, Japan+81 75 383 2506
Unité de Catalyse et de Chimie du Solide (UCCS). Cité Scientifique, ENSCL, bâtiment C7, Avenue Mendeleiev, 59650 Villeneuve d’Ascq - France+33 (0)3 20 33 64 34
Department of Materials Science and Engineering - McCormick School of Engineering - 2220 Campus Drive Cook 2036 Evanston, IL 60208-3109, USA+1 847 491 3198
Rodenbacher Chaussee 4, 63457 Hanau, Germany+49 6023 32039892