ANIONIC CONDUCTIVITY AND THERMAL-STABILITY OF SINGLE-CRYSTALS OF SOLID-SOLUTIONS BASED ON STRONTIUM FLUORIDE

The anionic conductivity of the anion-excess binary Sr1-xLaxF2+x (x=2X 10(-3), 0.2 and 0.4) and Sr0.8R0.2F2.2 (R=rare earths) and ternary Sr- 0.8(La1-yLuy)(0.2)F-2.2 (0 less than or equal to y less than or equal to 1) solid solutions with a fluorite-type structure was studied by im pedance spectroscopy at temperatures up to 1100 K. Single crystals, gr own from the melt by the Stockbarger technique, were used. At high tem peratures the conductivity plots display a considerable deviation from Arrhenius-type behaviour, caused by the Faraday phase transition in t hese materials. The results confirm the overall view on the transforma tion of the defect structure of the SrF2-based solid solutions, when v arying the rare-earth components in the series from La to Lu.