Solid electrolyte properties of LaF3

Abstract

The small-signal ac response of cells with LaF3 or the solid solutions La1-xBaxF3-x and ionically blocking electrodes has been measured in the frequency range 0.1-3 × 104Hz, and for temperatures from 220 to 650 K. The bulk electrolyte conductivity of LaF3 crystals is anisotropic up to 415 K. For polycrystalline samples grain boundary effects markedly influence the frequency dispersion. Above room temperature these effects mask the bulk electrolyte conductivity in the accessible frequency range. The composition dependence of the bulk electrolyte conductivity of La1-xBaxF3-x solid solutions is compared with 19F NMR data, and used to discuss recently reported association effects in LaF3. Reported anomalies in the electrical properties of LaF3 are used to exemplify the need to study the frequency dispersion over a wide frequency range.