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

Abstract

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 β-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 108–360 h in a fluorine atmosphere. Their conductivity σ is compared in correlation with the composition and structure type. The highest conductivity values are found for the tysonite Gd1 − yBayF3 − y phase (0.10 ≤ y ≤ 0.25): (1−2) × 10−3 S/cm at 683 K. The ordered Ba0.60Gd0.40F2.40 and Ba0.57Gd0.43F2.43 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.