High-Temperature Dielectric Relaxations in LiF Single Crystals.

By means of dielectric permittivity, electric modulus and impedance, the dielectric properties of LiF single crystals were investigated in the temperature range of 30°C-800°C and frequency range of 50 Hz-10 MHz. Two thermally activated relaxations, R1 and R2, were observed. The relaxation R1 showing activation energy around 0.8 eV was found to be related to the Li-ion diffusion in the crystal. The relaxation R2 contains three Arrhenius segments, the low-, mid-, and high-T segments, separated by boundary temperatures of 325°C and 425°C. These segments in the order of ascending temperature were found to be associated with F3, F3+ centers, F2 centers, and F centers, respectively. [ABSTRACT FROM AUTHOR]