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.