A NEUTRON POWDER DIFFRACTION STUDY OF THE LOW-TEMPERATURE AND HIGH-TEMPERATURE STRUCTURES OF BI12PBO19

We report the results of a high-resolution powder diffraction study of the low- and high-temperature structures of the compound Bi//1//2PbO//1//9. We find that at room and low temperatures a sillenite structure is adopted in which the anion vacancies are localized to specific locations on the sublattice. At high temperatures the material has a fluorite structure to that of delta Bi//2O//3. We discuss the relationship between the structure of the material and its electrical characteristics.