The relationship between ionic conductivity and structural characteristics of melt-grown KR3F10 (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) KDy3F10 and KHo3F10 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 KR3F10 (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 V1F per fluorine atom in a series of crystals with R = Tb, Dy, Ho and Y, the activation energy Eσ 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.