STUDIES OF RELAXATION PROCESSES IN BAF2-LA3+ CRYSTALS BY IONIC-THERMOCURRENT TECHNIQUES

Ionic thermocurrent (ITC) experiments have been performed on BaF2 single crystals doped with La3+ with concentrations ranging from 10-4 to 10-2 (molar fractions). For crystals with a concentration lower than 10-2, the spectrum consists of three peaks, A, B, and C. For the most-doped crystal there is an additional peak attributed to polarizable clusters. To calculate the dipole concentrations from the depolarization curves, a new method is presented. Based on the results of thermal treatments and concentration-dependent studies, peaks A and B are assigned to nearest-neighbor and next-nearest-neighbor dipoles, respectively. The relaxation parameters are EA=0.39 eV, 0=4.9×10-13 sec, EB=0.50 eV, and 0=3.4×10-12 sec. The effect of thermal and mechanical treatments on the highest-temperature peak is studied. It is proposed that the dislocations present in the crystal are responsible for this relaxation. © 1979 The American Physical Society.