Observation of Polarization Reversal Process in the Commensurate-Ferroelectric Phase of K2ZnCl4

Nematic liquid crystal technique, etching technique and powder technique have been applied to the study of the polarization reversal process in the commensurate-ferroelectric phase of K 2 ZnCl 4 . A single domain crystal undergoes polarization reversal through the sidewise expansion of domains nucleated at the predetermined locations in the bulk or at the crystal edges. The phase of the primary order parameters differs by π between the switched and unswitched regions, and the whole crystal is finally switched to a single domain. The polarization reversal process in a multidomain crystal is very complicated. The crystal can hardly be changed into a single domain state by the application of a dc field.