Ionic conductivity of the phases of five types formed in the BaF2-GdF3 system

The ionic conductivity has been measured in ceramic phases of five structure types found in the BaF₂-GdF₃ system: the fluorite type (CaF₂), its trigonal and tetragonal distortions, the tysonite type (LaF₃), and the orthorhombic ??-YF₃ modification. The phases have been obtained by solid-phase synthesis from BaF₂ and GdF₃ mixtures in hermetic nickel containers at 925, 964, and 1067°C for 108?C360 h in a fluorine atmosphere. Their conductivity ?? is compared in correlation with the composition and structure type. The highest conductivity values are found for the tysonite Gd_{1 ? y} Ba _y F_{3 ? y} phase (0.10 ?? y ?? 0.25): (1?2) × 10^?3 S/cm at 683 K. The ordered Ba_0.60Gd_0.40F_2.40 and Ba_0.57Gd_0.43F_2.43 phases with fluorite-derived structures and different degrees of order are characterized by the lowest conductivities: i(1.5?3.5 × 10^?5) S/cm.