Mechanism of electrotransport in superionic conductor Sr-=SUB=-0.7-=/SUB=-La-=SUB=-0.15-=/SUB=-Lu-=SUB=-0.15-=/SUB=-F-=SUB=-2.3-=/SUB=- with the fluorite-type structure

Abstract

The ionic conductivity of the superionic conductor Sr0.7La0.15Lu0.15F2.3 with the fluorite-type structure (type CaF2, sp. gr. Fm3m) had measured by the impedance spectroscopy in the temperature range 385-794 K. Bulk crystals of a three-component solid solution (lattice parameter a=5.7726(1) Angstrem) had obtained from the melt by the directed crystallization technique. Temperature dependence ionic conductivity sigmadc(T) satisfies the Arrhenius--Frenkel equation with the activation enthalpy of the electrical conductivity Delta Hsigma=0.706± 0.05 eV. The value of sigmadc is 1.5·10-5 S/cm at 500 K. Based on the analysis of electrophysical and structural studies of fluorite-type solid solutions in SrF2-LaF3 and SrF2-LuF3 systems, the microscopic model of ion transport in the Sr0.7La0.15Lu0.15F2.3 crystal was proposed. The concentration and mobility of charge carriers were calculated: nmob=7.8·1020 cm-3 and μmob=1.2·10-7 cm2/Vs at 500 K. Keywords: superionic conductors, impedance spectroscopy, single crystals, fluorides, rare earth ions, fluorite structure.