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RELATIONS STRUCTURES-PROPRIETES DANS LE SYSTEME Bi2O3-PbO-V2O5 : SURSTRUCTURES, POLYMORPHISME, INCOMMENSURABILITE et CONDUCTIVITE

Abstract : This work is focussing on the research for new materials containing bismuth with either specific new properties or improved properties of known materials, such as ionic conduction, in particular for their interest in the field of energy. Firstly, in the Bi2O3-PbO-V2O5 system, our work concerned the bismuth rich domain. The crystal structure of the compound PbBi6V2O15 was determined. The problem of identification by X-ray diffraction of respectively Bi3+ and Pb2+ was tackled by the replacement of lead by other M2+ cations such as Sr2+, Ca2+ and Cd2+. Structural determinations on single crystals revealed the existence of solid solution domains. On the basis of the Pb5Bi18V4O42 known structure, the substitution of Sr, Ca and Cd for Pb led to non-stoechiometric crystalline phases. In all cases, they are identified as superstructures deriving from the fluorite type Bi2O3-δ.
The second part of that study was devoted to the binary system BiVO4-nPbO. A phase transition α→β was characterized for the term n=1, PbBiVO5. The structures of "twinned" crystals were solved at room temperature and 530°C respectively, and the structural modifications occurring under the α→β transition precisely identified. PbBiPO5 undergoes a similar phase transition, while PbBiAsO5 crystallizes at ambient temperature under the β form.
Pb2BiVO6 (n=2) undergoes several structural transitions α, β and δ. Structures of the α and β forms were solved from single crystal data ; the resolution of the β structure required a 4D formalism. Two new forms α' and δ' were obtained by substituting Mn or P for V. Their crystal structures are closely related to respectively the α phase at room temperature, and the δ phase at 680°C. The electrical conductivities of all characterized materials were investigated and correlations were suggested between their conduction properties and their structural characteristics
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Olfa Labidi. RELATIONS STRUCTURES-PROPRIETES DANS LE SYSTEME Bi2O3-PbO-V2O5 : SURSTRUCTURES, POLYMORPHISME, INCOMMENSURABILITE et CONDUCTIVITE. Matériaux. Université des Sciences et Technologie de Lille - Lille I, 2006. Français. ⟨tel-00199221⟩

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