Pressure and temperature dependence of dielectric properties of Pb(Mg_1/2W_1/2)O₃

Abstract

The dielectric properties such as the permittivity, epsilon , and the dielectric loss tangent, tan delta , of Pb(Mg1/2W1/2)O3 were measured at various pressures up to 8 kbar. The permittivity epsilon obeys the Curie-Weiss law in the paraelectric phase at constant pressure. With increasing pressure p, the antiferroelectric transition temperature Tn decreases with a pressure coefficient dTn/dp=-3.8+or-0.2K kbar-1, the extrapolated Curie-Weiss temperature T0 increases with a pressure coefficient dT0/dp=1.4+or-0.2K kbar-1, the Curie constant C decreases at a rate of about 3.9% kbar-1, and the maximum value of epsilon , epsilon max, is almost constant at pressures below 4 kbar and then increases. The increase in epsilon max with p is associated with the decrease in the difference Delta T(=Tn-T0) with p. with increasing p, the difference Delta T decreases and extrapolates to zero at the pressure pt of about 18 kbar. At this pressure pt, the change from the antiferroelectric transition to the ferroelectric one is expected. At constant temperature, the pressure dependence of epsilon can be represented by a Curie-Weiss-like relationship expressed in terms of pressure: epsilon = epsilon 0*+C*/(p-p0). Both constants C* and p0 are functions of temperature. The dielectric properties associated with the antiferroelectric transition are interpreted in terms of a phenomenological theory.