High-Pressure Polymorphs of LaHO with Anion Coordination Reversal.

Two novel high-pressure polymorphs of lanthanum oxyhydride have been successfully predicted and stabilized under pressure. When reacted at 3 GPa, the fluorite structure of LaHO with anion-centered tetrahedral (HLa4/OLa4) geometry is transformed to the PbCl2-type structure involving coordination number increase of H- to five (HLa5 square pyramids). Upon further application of pressure to 5 GPa, LaHO changed into the anti Fe2P-type structure. Interestingly, the 5 GPa phase contains tetrahedral HLa4 and square-pyramidal OLa5 geometry, meaning coordination switching, as confirmed by ab initio calculations. The structural analysis shows that this unprecedented phenomenon is enabled by higher compressibility of hydride anion and emphasizes its potential in the search for new high-pressure forms of hydride-based mixed anion materials

Anion ordering enables fast H¯ conduction at low temperatures

H¯イオンの低温高速伝導を実現. 京都大学プレスリリース. 2021-06-03.Bringing order to hydrogen energy devices. 京都大学プレスリリース. 2021-06-03.The introduction of chemical disorder by substitutional chemistry into ionic conductors is the most commonly used strategy to stabilize high-symmetric phases while maintaining ionic conductivity at lower temperatures. In recent years, hydride materials have received much attention owing to their potential for new energy applications, but there remains room for development in ionic conductivity below 300°C. Here, we show that layered anion-ordered Ba2−δH3−2δX (X = Cl, Br, and I) exhibit a remarkable conductivity, reaching 1 mS cm⁻¹ at 200°C, with low activation barriers allowing H⁻ conduction even at room temperature. In contrast to structurally related BaH2 (i.e., Ba2H4), the layered anion order in Ba2−δH3−2δX, along with Schottky defects, likely suppresses a structural transition, rather than the traditional chemical disorder, while retaining a highly symmetric hexagonal lattice. This discovery could open a new direction in electrochemical use of hydrogen in synthetic processes and energy devices

Hydride-based antiperovskites with soft anionic sublattices as fast alkali ionic conductors

ソフトな陰イオンをもつ逆ペロブスカイト化合物で高速イオン伝導を達成. 京都大学プレスリリース. 2021-01-08.Most solid-state materials are composed of p-block anions, only in recent years the introduction of hydride anions (1s2) in oxides (e.g., SrVO2H, BaTi(O, H)3) has allowed the discovery of various interesting properties. Here we exploit the large polarizability of hydride anions (H–) together with chalcogenide (Ch2–) anions to construct a family of antiperovskites with soft anionic sublattices. The M3HCh antiperovskites (M = Li, Na) adopt the ideal cubic structure except orthorhombic Na3HS, despite the large variation in sizes of M and Ch. This unconventional robustness of cubic phase mainly originates from the large size-flexibility of the H– anion. Theoretical and experimental studies reveal low migration barriers for Li+/Na+ transport and high ionic conductivity, possibly promoted by a soft phonon mode associated with the rotational motion of HM6 octahedra in their cubic forms. Aliovalent substitution to create vacancies has further enhanced ionic conductivities of this series of antiperovskites, resulting in Na2.9H(Se0.9I0.1) achieving a high conductivity of ~1 × 10–4 S/cm (100 °C)

Caractérisations structurales in situ avancées d'oxydes dérivées de la pérovskite pour des applications électrochimiques à haute température

This thesis is focused on oxides related to perovskite such as K2NiF4 structure-type, double perovskite and brownmillerite with mixed conduction properties. This ability to conduct both oxygen ions and electrons is relevant for electrochemical devices operating at high temperature, particularly as an electrode for solid oxide fuel cell. Specifically, this thesis deals with the synthesis and advanced crystal structure characterization of the reactivity of these materials mainly through large scale facilities by means of neutron powder diffraction (NPD) and X-ray synchrotron. Preliminary work in these studies involves inorganic synthesis by solid-state or by sol-gel route, thermogravimetric analysis and the iodometric titration. Original reactivity cells have been developed at the ISCR to study redox behavior under different gas flow and as a function of temperature for both neutron diffraction and X-ray synchrotron experiment. In situ study by NPD of La2-xSrxMnO4 ± δ compounds where x = 2.0 and x = 0.8 which derived from the compound cathode reference La1-xSrxMnO3 allowed to follow the structural evolution as a function of δ in reducing conditions for x = 2.0 and oxidizing conditions for x = 0.8. The synchrotron study of Pr2NiO4.22 helped to highlight the monoclinic symmetry at room temperature while previous studies announced an orthorhombic symmetry. Besides, structural changes including the transition to the HTT phase are accompanied by an incommensurable modulation that persists at least up to 900 °C. The study of double perovskites NdBaCo2-xMnxO5+δ where 0 ≤ x ≤ 2 showed that these materials exhibit a promising electrical conductivities for SOFC applications as cathode. In addition, the comparison of the molecular dynamics and NDP combined with MEM for x = 0 compound has elucidated the oxygen diffusion mechanism in these compounds. The study by NPD in reducing condition of LaSrFeCoO6 to the brownmillerite LaSrFeCoO5 has showed that the reduced structure persists at high temperatures and allowed to follow the evolution in the ordering of the magnetic moments while cooling LaSrFeCoO5.Ce travail de thèse se situe dans la thématique des oxydes dérivés de la pérovskite ayant des propriétés de conduction mixte tels que les structures de type K2NiF4, les pérovskites doubles et la brownmillérite. Cette aptitude à conduire à la fois l'oxygène et les électrons présente un intérêt pour des dispositifs électrochimiques fonctionnant à haute température et notamment en tant qu'électrode pour les piles à combustible à oxyde solide. Plus précisément, cette thèse concerne la synthèse et l'étude cristallochimique avancée de la réactivité de ces matériaux essentiellement par les grands instruments par le biais de la diffraction de neutrons (NPD) et des rayons X synchrotron. Le travail préliminaire à ces études implique de la synthèse inorganique par voie solide ou par voie sol-gel, l'analyse thermogravimétrique et la titration iodométrique. Des cellules de réactivité originales ont été développées spécialement à l'ISCR pour l'étude in situ du comportement redox sous différents flux gazeux et en fonction de la température à la fois dans le cadre de la diffraction des neutrons et rayons X synchrotron. L'étude in situ par NPD des composés La2-xSrxMnO4±δ où x = 2,0 et x = 0,8 qui dérivent du composé de cathode de référence La1-xSrxMnO3 a permis de suivre l'évolution structurale en fonction du δ en conditions réductrices pour x = 2,0 et en conditions oxydantes pour x = 0,8. L'étude DRX synchrotron de Pr2NiO4,22 a permis de mettre en évidence la symétrie monoclinique à température ambiante alors que les études précédentes annonçaient une symétrie orthorhombique. Les variations structurales notamment la transition vers la phase HTT sont accompagnées d'une modulation incommensurable qui persiste jusqu'à au moins 900 °C. L'étude des pérovskites doubles NdBaCo2−xMnxO5+δ où 0 ≤ x ≤ 2 a permis de montrer que ces matériaux présentent des conductivités électriques totales très prometteuses pour des applications en tant que cathode de SOFC. De plus, la confrontation de la dynamique moléculaire et de la NPD combinée à la MEM pour le composé x = 0 a permis d'élucider le mécanisme de diffusion de l'oxygène dans cette famille de composés. L'étude par NPD de la réduction de LaSrFeCoO6 vers LaSrFeCoO5 de structure brownmillérite a permis de mettre en évidence que la structure réduite persiste à haute température et l'évolution de la mise en ordre des moments magnétiques lors du refroidissement de LaSrFeCoO5

Advanced crystal characterization in situ of oxides related to perovskite for high temperature electrochemical devices

Ce travail de thèse se situe dans la thématique des oxydes dérivés de la pérovskite ayant des propriétés de conduction mixte tels que les structures de type K2NiF4, les pérovskites doubles et la brownmillérite. Cette aptitude à conduire à la fois l'oxygène et les électrons présente un intérêt pour des dispositifs électrochimiques fonctionnant à haute température et notamment en tant qu'électrode pour les piles à combustible à oxyde solide. Plus précisément, cette thèse concerne la synthèse et l'étude cristallochimique avancée de la réactivité de ces matériaux essentiellement par les grands instruments par le biais de la diffraction de neutrons (NPD) et des rayons X synchrotron. Le travail préliminaire à ces études implique de la synthèse inorganique par voie solide ou par voie sol-gel, l'analyse thermogravimétrique et la titration iodométrique. Des cellules de réactivité originales ont été développées spécialement à l'ISCR pour l'étude in situ du comportement redox sous différents flux gazeux et en fonction de la température à la fois dans le cadre de la diffraction des neutrons et rayons X synchrotron. L'étude in situ par NPD des composés La2-xSrxMnO4±δ où x = 2,0 et x = 0,8 qui dérivent du composé de cathode de référence La1-xSrxMnO3 a permis de suivre l'évolution structurale en fonction du δ en conditions réductrices pour x = 2,0 et en conditions oxydantes pour x = 0,8. L'étude DRX synchrotron de Pr2NiO4,22 a permis de mettre en évidence la symétrie monoclinique à température ambiante alors que les études précédentes annonçaient une symétrie orthorhombique. Les variations structurales notamment la transition vers la phase HTT sont accompagnées d'une modulation incommensurable qui persiste jusqu'à au moins 900 °C. L'étude des pérovskites doubles NdBaCo2−xMnxO5+δ où 0 ≤ x ≤ 2 a permis de montrer que ces matériaux présentent des conductivités électriques totales très prometteuses pour des applications en tant que cathode de SOFC. De plus, la confrontation de la dynamique moléculaire et de la NPD combinée à la MEM pour le composé x = 0 a permis d'élucider le mécanisme de diffusion de l'oxygène dans cette famille de composés. L'étude par NPD de la réduction de LaSrFeCoO6 vers LaSrFeCoO5 de structure brownmillérite a permis de mettre en évidence que la structure réduite persiste à haute température et l'évolution de la mise en ordre des moments magnétiques lors du refroidissement de LaSrFeCoO5.This thesis is focused on oxides related to perovskite such as K2NiF4 structure-type, double perovskite and brownmillerite with mixed conduction properties. This ability to conduct both oxygen ions and electrons is relevant for electrochemical devices operating at high temperature, particularly as an electrode for solid oxide fuel cell. Specifically, this thesis deals with the synthesis and advanced crystal structure characterization of the reactivity of these materials mainly through large scale facilities by means of neutron powder diffraction (NPD) and X-ray synchrotron. Preliminary work in these studies involves inorganic synthesis by solid-state or by sol-gel route, thermogravimetric analysis and the iodometric titration. Original reactivity cells have been developed at the ISCR to study redox behavior under different gas flow and as a function of temperature for both neutron diffraction and X-ray synchrotron experiment. In situ study by NPD of La2-xSrxMnO4 ± δ compounds where x = 2.0 and x = 0.8 which derived from the compound cathode reference La1-xSrxMnO3 allowed to follow the structural evolution as a function of δ in reducing conditions for x = 2.0 and oxidizing conditions for x = 0.8. The synchrotron study of Pr2NiO4.22 helped to highlight the monoclinic symmetry at room temperature while previous studies announced an orthorhombic symmetry. Besides, structural changes including the transition to the HTT phase are accompanied by an incommensurable modulation that persists at least up to 900 °C. The study of double perovskites NdBaCo2-xMnxO5+δ where 0 ≤ x ≤ 2 showed that these materials exhibit a promising electrical conductivities for SOFC applications as cathode. In addition, the comparison of the molecular dynamics and NDP combined with MEM for x = 0 compound has elucidated the oxygen diffusion mechanism in these compounds. The study by NPD in reducing condition of LaSrFeCoO6 to the brownmillerite LaSrFeCoO5 has showed that the reduced structure persists at high temperatures and allowed to follow the evolution in the ordering of the magnetic moments while cooling LaSrFeCoO5

Structure and Reactivity of the La_2-<i>x</i>Sr_<i>X</i>MnO_4±δ (0.7≤ <i>X ≤</i>1.0) Solid Solutions in Oxidizing Condition

International audienc

Redox behaviour of potential SOFC cathode materials La1.6Sr0.4Ni1-​xCoxO4+δ (x = 0.6 and 0.8) determined from in situ neutron powder diffraction under flowing O2 and 5​%H2

International audienc

Prevalentie van respiratoire pathogenen in neusswabs van paarden met acute ademhalingsstoornissen in België

Contagious respiratory infections are an important cause of respiratory disease in horses, resulting in impaired pulmonary function, poor performance and sometimes severe illness. Although bacterial infections are often suspected to be involved, viruses are frequently overlooked and are an underestimated cause of respiratory disease outbreaks in horses. In this study, nasal swabs of 103 horses with acute symptoms of respiratory disease were analyzed for the presence of 13 different respiratory pathogens. Gamma herpesviruses were the most commonly detected, with 60% of the samples being positive, followed by streptococcus equi subsp. zooepidemicus infection (30%). Rhinovirus B, streptococcus equi subsp. equi, adenovirus 1 and EHV-4 were more rarely detected. Further research is necessary to correctly interpret the importance of gamma herpesviruses in horses, for example by screening a healthy control population. National surveillance of respiratory viruses in horses by PCR analysis on nasal swabs might be a useful, earlywarning system for viral epidemics.Infectieuze aandoeningen zijn een belangrijke oorzaak van ademhalingsproblemen bij paarden. Ze kunnen aanleiding geven tot een verstoorde longfunctie, verminderde prestaties en soms ernstige klinische ziekte. Hoewel meestal bacteriële infecties vermoed worden, zijn virussen een onderschatte oorzaak van besmettelijke ademhalingsinfecties bij paarden. In deze studie werden neusswabs genomen bij 103 paarden met symptomen van acute ademhalingsinfectie en gescreend op de aanwezigheid van 13 verschillende equine ademhalingspathogenen. Gammaherpesvirussen waren, met 60% positieve stalen, de meest gedetecteerde pathogenen, gevolgd door streptococcus equi subsp. zooepidemicus infecties (30%). Rhinovirus B, streptococcus equi subsp. equi, adenovirus 1 en EHV-4 werden minder frequent gevonden. Verder onderzoek is nodig om het belang van gammaherpesvirussen bij het paard correct te interpreteren. Nationale surveillance van ademhalingsvirussen bij paarden door middel van PCR-analyse op neusswabs zou een nuttig waarschuwingssysteem voor dreigende virale epidemieën kunnen zijn

Density functional theory-assisted 31P and 23Na magic-angle spinning nuclear magnetic resonance study of the Na3V2(PO4)2F3–Na3V2(PO4)2FO2 solid solution: unraveling Its local and electronic structures

The local and electronic structures of Na3V2(PO4)2F3–Na3V2(PO4)2FO2 electrode materials have been investigated by a combination of 23Na and 31P magic-angle spinning NMR spectroscopy and density functional theory calculations. The spin distributions and the 31P NMR Fermi contact shifts in these materials are calculated based on the projector augmented wave approach implemented in the VASP code. Upon oxygen substitution, V4+ ions are formed and involved in highly covalent vanadyl bonds. We show that they exhibit a very specific electronic structure with a single electron on the 3dxy orbital perpendicular to the bi-octahedra axis. The V3+ ions, on the other hand, exhibit a partial occupation of the t2g orbitals by two electrons. The peculiar electronic structure of the V ions is at the origin of the complex spin transfer mechanisms observed in the Na3V2(PO4)2F3–Na3V2(PO4)2FO2 materials and results in the existence of several 23Na and 31P MAS NMR resonances. Owing to the proper signal assignment achieved using DFT calculations, we could estimate the degree of oxygen substitution for fluorine in the materials and discuss the local distribution of V3+/V4+ ions. Furthermore, through the 31P NMR study on the Na3V2(PO4)2FO2 composition, we here demonstrate that a 31P NMR resonance close to 0 ppm can also be observed in paramagnetic materials if there is no proper orbital overlap for the electron spin transfer to occur. Thanks to the proper signal assignment achieved using DFT calculations, we couldestimate the degree of substitution of oxygen for fluorine in the materialsand discuss the local distribution of V3+/V4+ionsBatteries à ions sodium pour des robots télécommandé

V^IV disproportionation upon sodium extraction from Na3V2(PO4)2F3 observed by operando x-ray absorption spectroscopy and solid-state NMR

Among the series of polyanionic positive electrodes for sodium-ion batteries having the general formula Na3V2(PO4)2F3–yOy (0 ≤ y ≤ 2), the composition Na3V2(PO4)2F3 (y = 0) has the highest theoretical energy that offers competitive electrochemical performances compared to sodium transition metal oxides. Recently, the structural phase diagram from Na3V2(PO4)2F3 to Na1V2(PO4)2F3 has been thoroughly investigated by operando synchrotron X-ray diffraction revealing an unexpected structural feature for the end member composition. In fact, the crystal structure of Na1V2(PO4)2F3 has two very different vanadium environments within each bioctahedron that suggests a charge disproportionation of two VIV into VIII and VV. This work shows an operando X-ray absorption spectroscopy at vanadium K edge during the electrochemical extraction of Na+ in order to monitor the redox processes involved in this compound. The large data set provided by this experiment has been processed by the principal component analysis combined with multivariate curve resolution. The results suggest that the bioctahedra have to be considered as the basic structural unit. The peculiar geometry of this material combined with the mixed vanadium valence, directly investigated here along the reaction, seems to allow original electronic configurations. In particular, the two vanadium sites into the basic bioctahedra unit evolve from VIII–VIII to VIII–VIV and to a final VIII–VIV configuration. These observations are completed with 51V NMR sensitive to diamagnetic V^V.Laboratory of excellency for electrochemical energy storageBatteries à ions sodium pour des robots télécommandésNa-Ion bAttery Demonstration for Electric Storag