Change in the Order of the Phase Transition in Ferroelectric Triglycine Selenate at High Pressures

Abstract

Dielectric constant of ferroelectric triglycine selenate was measured at hydrostatic pressures around 5 kbar in the vicinity of the Curie temperature. A discontinuous charge of the dielectric constant at the Curie temperature and a thermal hysteresis of the transition (typically about 0.2°C at 5.28 kbar) were found. The result indicates that the order of the ferroelectric transition changes from second to first order by application of hydrostatic pressure. Unusual dielectric properties of TGSe at high pressures so far reported can be interpreted on the basis of the order-change in the transition.