Dielectric relaxation of ZnF2: LiF

Abstract

The thermally activated release of the dielectric polarization of ZnF₂: LiF crystals measured by the ionic thermoconductivity method is examined in terms of vacancy and interstitialcy models. The previously proposed vacancy model is reviewed and an interstitialcy model is introduced. (Li⁺–V_F) and (Li⁺–Li_i⁺) dipolar defects are proposed and the change in dipole orientation causing the current discharge is examined in relation to possible anion vacancy and interstitial cation movements. The relaxation process has been found to be very anisotropic and is characterized by the relaxation time, τ(T)=1.70×10⁻¹³ exp (0.32/kT). It is proposed that the dipolar relaxation is due to the (Li⁺–Li_i⁺) ion pair and that the rotation of the dipolar efect is accomplished by interstitial lithium‐ion movements parallel to the c axis of the crystal.