Studies of the electrical properties of nearly perfect K 2ZnCl 4 single crystals as measured during commensurate incommensurate-paraelectric phase transitions

Abstract

Electrical conductivity and dielectric measurements were carried in the temperature range covering the commensurate ferroelectric–incommensurate-paraelectric normal phases (300–600 K) for the three main crystallographic axes of K 2ZnCl 4 single crystals. The values of activation energies in the three phases were calculated and discussed. A thermal hysteresis of about 12 K is observed which deduce the presence of first order transition for the lock-in ferroelectric transition at T c=404 K. Conductivity anomalies were observed in both ferroelectric and paraelectric phases. The conduction mechanism was discussed. The suggested occurrence of discommensuration in K 2ZnCl 4 crystals upon the lock-in transition in contrast with conductivity and dielectric results explains the anomalous behavior for the b-axis measurements. The orientation of these discommensuration was discussed on a view of projection in the three standard crystallographic directions.