CRYSTAL STRUCTURE OF SOME NEW PHASES IN THE SYSTEM Bi₂O₃-PbO-P₂O₅

Abstract

Three new phases were identified in the ternary system Bi₂O₃-PbO-P₂O₅: PbBiPO₅, Pb₄BiPO₈ and Pb₅Bi₁₈P₄O₄₂. PbBiPO₅ displays a phase transformation from triclinic to monoclinic symmetry at 725°C. The crystal structures of Pb₄BiPO₈ and Pb₅Bi₁₈P₄O₄₂ were solved from single crystal diffraction data. The formula described previously as PbBi₃PO₈ was revised and is more likely Pb₃Bi₁₀P₃O_25.5, equivalent to PbBi_3.33PO_8.5. Its crystal structure displays a distorded 3 x 3 x 3 superstructure of a tetragonal variety of 3δ-Bi₂O₃ type