The anionic conductivity of anion-excess solid solutions, Sr1−xLaxF2+x (x = 0.002, 0.2 or 0.4), Sr0.8R0.2F2.2 (R = rare earth) and Sr0.8(La1−yLuy)0.2F2.2 (y = 0 to 1), with a fluorite structure was studied by means of impedance spectroscopy at up to 1100K. Single crystals which had been grown from the melt by using the Stockbarger technique were used. At high temperatures, the conductivity plots exhibited considerable deviations from Arrhenius-type behavior, due to a Faraday phase transition in the materials. The results confirmed the overall consensus that a transformation of the defect structure of SrF2-based solid solutions occurred upon varying the rare-earth component from La to Lu.

Anionic Conductivity and Thermal Stability of Single Crystals of Solid Solutions based on Strontium Fluoride. N.I.Sorokin, M.W.Breiter: Solid State Ionics, 1997, 104[3-4], 325-33