Electric conductivity of heterovalent substitution solid solutions of the (1–x)PbF2–xYF3–SnF2 system

Abstract

Heterovalent substitution solid solutions of tetragonal modification isostructural with β-PbSnF₄ and having fluoride anions localized in three structurally nonequivalent positions are formed in the (1–x)PbF₂–xYF₃–SnF₂ system in the concentration range 0 < x ≤ 0.17. The conductivity of the synthesized samples is provided by the interstitial fluoride anions and is independent of the concentration of the heterovalent substituent at temperatures below 300 K. The contribution of the surface conductivity of the crystallites of the synthesized samples to the total bulk conductivity was not found. The temperature dependences of electric conductivity of each of the synthesized samples show an inflection at 435–475 K, which is due to the increased mobility of fluoride anions at elevated temperatures. The transport numbers of the fluoride anions are close to unity over the whole range of concentrations of the synthesized samples and are almost independent of the YF₃ concentration. The electronic conductivity of the samples was two orders of magnitude lower than the ionic conductivity.