The relationship between ionic conductivity and structural characteristics of melt-grown KR 3F10 (R = Tb, Dy, Ho, Y) single crystals

Abstract The temperature dependences of the ionic electrical conductivity of fluorite-type (sp. gr. F m 3 ‾ m $Fm\overline{3}m$ , Z = 8) KDy 3 F 10 and KHo 3 F 10 single crystals grown by the Bridgman technique have been studied by impedance spectroscopy for the first time. The correlation between the conductometric and structural characteristics of K R 3 F 10 ( R = Tb, Dy, Ho, Y) crystal family from the point of view of the observed size effect in the ionic conductivity is discussed. With decrease in the unit-cell volume V 1F per fluorine atom in a series of crystals with R = Tb, Dy, Ho and Y, the activation energy E σ of ion transfer decreases from 1.57 to 1.16 eV respectively and the fluorine-ion conductivity value increases from 3.0 × 10 −5 to 4.4 × 10 −4 S cm at 773 K, i.e. the nature of the conductivity change is linearly antibatic. This phenomenon can be useful for developing approaches and search strategies for new ionic conductors.