Etude des proprietes structurales et electriques de la solution solide Pb1−xBixOxF2−x

An investigation of the PbF₂BiOF system at 600°C has allowed to isolate a Pb_1-xBi_xO_xF_2-x solid solution for x ? 0.67 the structure is of fluorite type and for 0.67 < × ? 0.80 it presents a fluorite derived rhombohedral distortion. The ionic conductivity has been examined. For × ? 0.50 Pb_1-xBi_xO_xF_2-x has electrical performances of the same order than those of the best so far known fluorides. Bragg neutron diffraction investigations have been carried out in order to account for the electrical behavior of the cubic solid solution (0 < x ? 0.67). The distribution of the anions between normal and interstitial sites is given as a function of substitution rate. The structure has been described on the basis of local BiOF-type clusters. The formation of isolated antiprisms BiX₈ (X = O,F) allows to understand the evolution of the electrical properties.