Dielectric Study on the Phase Transitions in Triglycine Selenate-Deuterated Triglycine Selenate System

Abstract

Ferroelectric phase transitions in the solid solution of triglycine selenate (NH 2 CH 2 COOH) 3 ·H 2 SeO 4 (TGSe) and deuterated triglycine selenate (ND 2 CH 2 COOD) 3 ·D 2 SeO 4 (DTGSe) were studied by means of dielectric-constant measurements. The Curie point monotonically increases with increasing deuterium content from 22.3°C for TGSe to 35°C for DTGSe. The deuterium-substitution induces a discontinuous change in dielectric constant at the transition accompanied with a thermal hysteresis of the Curie point. The first order nature of the transition becomes more and more conspicuous as the deuterium-content increases. The critical deuterium content at which the order of the transition changes from second to first seems to be very low.