Fluorite-like phases in the BaF2–BiF3–Bi2O3 system—synthesis, conductivity and defect clustering

A fluorite-like solid solution Ba1 − xBixOzF2 + x − 2z on the basis of cubic BaF2 was synthesised in the BaF2–Bi2O3–BiF3 system and the homogeneity range at 873 K was determined. The samples were studied by X-ray powder diffraction and electron diffraction, and their transport properties were measured by the complex impedance method at 300–623 K. Tendencies of variation of lattice parameters and transport properties were determined. These tendencies are discussed on the basis of a defect clustering hypothesis. Thermal treatment at 573 K of the solid solution, quenched from 873 K results in the formation of a new ordered tetragonal fluorite-like phase with lattice parameters a = 9.5355(4) Å, c = 18.151(1) Å.