Solid phase synthesis and characterization of new BIMEVOX series: Bi(4)V(2-x)M(x)O(11-x) (M=Cr-III, Fe-III)

Two new BIMEVOX series Bi(4)V(2-x)M(x)O(11-x) (M = Cr-III, Fe-III) have been investigated by X-ray powder diffraction, thermal analysis and ionic conductivity measurements. Structural phase transitions alpha <----> beta and beta <----> gamma occur as a function of composition and temperature in iron substituted phases for which a new orthorhombic domain is evidenced when x exceeds 0.5. At low temperature, the Cr compounds retain the alpha orthorhombic symmetry where an incommensurate structural modulation is observed. The structure of the tetragonal phase Bi4V1.5Fe0.5O10.5 has been refined by the Rietveld method. The anionic properties are compared to those of other iso- or aliovalent cation substituted BIMEVOX and discussed in terms of electronic configuration and site preference of the doping cation.