STUDY OF NEW CONDUCTIVE OXYFLUORIDES BASED ON BISMUTH, VANADIUM, ZINC

Syntheses in the Bi2O3-V2O5-ZnF2 system at 700 C have resulted in the isolation of a glass domain, named G, and a crystallised phase, named C, located near the Bi2O3-ZnF2 line. Structural determination by XRD showed that the C phase is related to Bi2MoO6. Fluorine ions are mainly located in Bi2O2(2+) sheets in order to form Bi2F4(4+) layers, the other F- ions are located in the perovskite layers. However, the compound's formula in this part of the diagram leads to a ZnO excess in comparison with the Bi2MoO6 formula. Raman diffusion spectroscopy confirmed the existence of a vitreous network within the perovskite layer in which the ZnO excess could be inserted. The vitreous compounds corresponding to G phase, recrystallised into the isomorphous C phase and evidenced by conductivity measurements, present glass-ceramic type properties. The glass-ceramic sigma values are 50 times higher than vitreous compounds (sigma = 4 x 10 exp(-4) S/cm at 260 C for Bi0.65Zn1.215V0.135O1.313F2.43). 11 refs.