Dielectric Relaxation in PbF2 - Doped and X-ray Irradiated CaF2 Crystals

Abstract

Temperature and frequency dependence of the complex dielectric constant give information about the relaxation processes and permits the determination of the activation energy and the reciprocal frequency factor of the relaxation time. Pure and various concentration PbF 2 -doped CaF 2 crystals have been grown using the vertical Bridgman method. The thin disks cut from the crystals have been X-ray irradiated. Room temperature optical absorption spectra were recorded for pure, doped and x-ray irradiated samples. Capacitance and dielectric loss measurements were performed on the samples over the temperature range 150-300 K at 1-100 kHz, and then the imaginary part of the dielectric constant has been calculated. The dielectric properties have been measured before and after X-ray irradiation, the activation energy and the reciprocal frequency factor have been calculated in order to characterize the observed relaxations.