Innovative inorganic compounds by manipulation and diversification of the anionic sublattice

Ce manuscrit détaille la découverte de nouveaux matériaux oxydes et oxysulfures. Dans un premier temps, il porte sur l’étude de composés hexagonaux RM2O4 et R2M3O7 modifiés topotactiquement par oxydation. Les deux composés métastables, YbFe2O4.5 et InFe2O4.5, montrent la conservation du caractère multicouche via un jeu de glissement des couches de fer et de terre rare et une réorganisation du sous-réseau anionique. Les structures modulées présentent une distribution unique de polyèdres FeOn (n = 4, 5 et 6). En revanche, le composé InGaFeO4.3 met en évidence la particularité des cations Ga3+ à bloquer le réarrangement structural. Les composés R2M3O7 (Yb2Fe3O7.5 et In2Ga2MnO7.12) contiennent les unités RM2O4 déjà décrites et, donc, présentent les mêmes phénomènes d’oxydation. Dans un second temps, l’étude se concentre sur la recherche de nouveaux oxysulfures de basse dimensionnalité, en s’inspirant notamment des composés Ba3VS3(VO3S) et La3SiS4(CuS3). Les phases inédites Ba10V6S7O18 et Ba10.67V3O6Fe8.67S17.33 ont été obtenues avec une charpente de basse dimension rendue possible par la présence de cations Ba2+ et d’entités V(O,S)4 qui jouent le rôle de séparateurs. La première phase ouvre la voie à de l’ingénierie du band gap à partir des différents types d’anions dont des soufres « isolés ». Les deux autres nouvelles phases Ba3(V,Cr)S3(VO3S) et La3Cu0.5 2δFe0.25+δSiS7 sont constituées de chaines ((Cr/V)3+S3 et (Fe2+/Cu+)S3 déficientes) séparées par des entités tétraédriques (VO3S et SiS4). Cette étude se termine sur la détermination structurale de Co7S8, un composé binaire du système Co-S, et la découverte de son comportement métallique non conventionnel.This manuscript details the discovery of new oxide and oxysulfides materials. First, it focuses on the study of hexagonal compounds RM2O4 and R2M3O7 topotactically modified by oxidation. The two metastable compounds, YbFe2O4.5 and InFe2O4.5, show the conservation of the multilayer feature via a sliding of the iron’s and rare earth’ layer and a reorganization of the anionic sublattice. The modulated structures have a unique distribution of FeOn polyhedra (n = 4, 5 and 6). In contrast, the InGaFeO4.3 compound shows the particularity of Ga3+ cations to block the structural rearrangement. The R2M3O7 (Yb2Fe3O7.5 and In2Ga2MnO7.12) compounds have the RM2O4 units already discussed and, therefore, exhibit the same phenomenon of oxidation. Secondly, the study focuses on the research of new oxysulfides of lower dimension, by focusing on the compounds Ba3VS3(VO3S) and La3SiS4(CuS3). Two new structures Ba10V6S7O18 et Ba10.67V3O6Fe8.67S17.33 have been obtained with a low dimension framework made possible by the presence of Ba2+ cations and V(O,S)4 entities which are separators. The first phase opens the way to band gap engineering from the different types of anions including “isolated” sulfurs. The two other new phases Ba3(V,Cr)S3(VO3S) and La3Cu0.5 2δFe0.25+δSiS7 are made up of chains ((Cr/V)3+S3 and deficient (Fe2+/Cu+)S3) separated by tetrahedral entities (VO3S and SiS4).This study is conclude with the structural determination of Co7S8, a binary compound of Co-S system, and the discovery of it unconventional metallic behavior

The Ba 10 S(VO 3 S) 6 Oxysulfide: 1D-Structure and Mixed Anion Chemical Bonding

International audienceThe new oxysulfide Ba10V6S7O18, that can be written as Ba10S(VO3S)6, was prepared by solid state reaction. It crystallizes in the non-centrosymmetric P63 space group with the unit cell parameters a=18.3018(2) Å and c=8.6525(2) Å, R1 = 3.21%. This original phase exhibits (VO3S) units separated by Ba 2+ cations, the later delimit 1D-hexagonal-like cavities filled by disordered sulfur S 2anions and arranged into two kinds of sulfur-deficient 1D-channels. DFT calculations were employed to get insights into the chemical bonding and parameters ruling the structure, particularly the V-O vs. V-S bonding inside the mixed anion VO3S tetrahedra, and the contribution of the S 2of the cavities. The title compound can be decomposed with three components mainly interacting by ionic bonds as follows, Ba10V6S7O18 → [Ba10] 20+ [S] 2-[(VO3S)6] 18-, this description may pave the way to the design of other phases related to this system with adjusted band gap features. In particular, the effect of the V(O,S)4/Ba ratio is discussed to emphasize the presence of the [S] 2component, in comparison with related structures such as Ba6V4O5S11 [Ba6(VO2S2)2(VS3O)(VS4)], as it contributes strongly just below the fermi level with subsequent alteration of the band gap

Recent Exotic Topotactic Modifications of Magnetic oxides

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Design of New Oxychalcogenides From Heteroleptic Building Blocks

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New low dimensional inorganic topologies from mixed anion building blocks

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Crystal Chemistry of vacancies and interstitial anions in layered multiferroics

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Modélisation structurale et étude de nouveaux composés inorganiques fonctionnels à partir d’entités structurales hétéroleptiques

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Nouvelles Topologies Inorganiques par Modification/Diversification du Sous-Réseau Anionique

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Comprehensive Study of Oxygen Storage in YbFe2O4+x (x ≤ 0.5): Unprecedented Coexistence of FeOn Polyhedra in One Single Phase

International audienceThe multiferroic LuFeO was recently proposed as a promising material for oxygen storage due to its easy reversible oxidation into LuFeO. We have investigated the similar scenario in YbFeO, leading to a slightly greater oxygen storage (OSC) capacity of 1434 μmol O/g. For the first time, the structural model of LnFeO was fully understood by high-resolution microscopy images, and synchrotron and neutron diffraction experiments, as well as maximum entropy method. The oxygen uptake promotes a reconstructive shearing of the [YbO] sub-units controlled by the adaptive Ln/Fe oxygen coordination and the Fe redox. After oxidation, the rearrangement of the Fe coordination polyhedra is unique such that all available FeO units (n = 6, 5, 4 in octahedra, square pyramids, trigonal bipyramids, tetrahedra) were identified in modulated rows growing in plane. This complex pseudo-ordering gives rise to short-range antiferromagnetic correlation within an insulating state

Comprehensive study of oxygen storage in YbFe2O4+x (x ≤ 0.5): unprecedented coexistence of FeOn polyhedra in one single phase

The multiferroic LuFeO was recently proposed as a promising material for oxygen storage due to its easy reversible oxidation into LuFeO. We have investigated the similar scenario in YbFeO, leading to a slightly greater oxygen storage (OSC) capacity of 1434 μmol O/g. For the first time, the structural model of LnFeO was fully understood by high-resolution microscopy images, and synchrotron and neutron diffraction experiments, as well as maximum entropy method. The oxygen uptake promotes a reconstructive shearing of the [YbO] sub-units controlled by the adaptive Ln/Fe oxygen coordination and the Fe redox. After oxidation, the rearrangement of the Fe coordination polyhedra is unique such that all available FeO units (n = 6, 5, 4 in octahedra, square pyramids, trigonal bipyramids, tetrahedra) were identified in modulated rows growing in plane. This complex pseudo-ordering gives rise to short-range antiferromagnetic correlation within an insulating state