Anionic conductivity and thermal stability of single crystals of solid solutions based on strontium fluoride

Abstract

The anionic conductivity of the anion-excess binary Sr 1− x La x F 2+ x ( x=2×10 −3, 0.2 and 0.4) and Sr 0.8R 0.2F 2.2 (R=rare earths) and ternary Sr 0.8(La 1− y Lu y ) 0.2F 2.2 (0≤ y≤1) solid solutions with a fluorite-type structure was studied by impedance spectroscopy at temperatures up to 1100 K. Single crystals, grown from the melt by the Stockbarger technique, were used. At high temperatures the conductivity plots display a considerable deviation from Arrhenius-type behaviour, caused by the Faraday phase transition in these materials. The results confirm the overall view on the transformation of the defect structure of the SrF 2-based solid solutions, when varying the rare-earth components in the series from La to Lu.