Two forms of polarization relaxation in polydomain ferroelectrics in an electric field

The characteristic features of the polarization and depolarization kinetics of polydomain ferroelectrics with square and narrow "extended'' dielectric hysteresis loops are investigated for the model of TGS and Rb2ZnCl4 crystals. It is shown that for the second crystal, in contrast to the first crystal, the local free energy is asymmetric relative to the direction of polarization, the coercive field does not have a definite value, and only part of the crystal volume participates in the slow thermoactivational relaxation. The slow relaxation follows a universal empirical power law in all cases. The distribution functions of the relaxation times in crystals are constructed on the basis of experimental data, and comparative estimates are made of the relaxation parameters and the parameters of the energy barriers for domain walls. (C) 1999 American Institute of Physics. [S1063-7834(99)02503-4].