Pressure and temperature dependence of dielectric properties of Pb(Mg1/2W1/2)O3

The dielectric properties such as the permittivity, epsilon , and the dielectric loss tangent, tan delta , of Pb(Mg 1/2 W 1/2 )O 3 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 T n decreases with a pressure coefficient dT n /dp=-3.8+or-0.2K kbar -1 , the extrapolated Curie-Weiss temperature T 0 increases with a pressure coefficient dT 0 /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(=T n -T 0 ) with p. with increasing p, the difference Delta T decreases and extrapolates to zero at the pressure p t of about 18 kbar. At this pressure p t , 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-p 0 ). Both constants C* and p 0 are functions of temperature. The dielectric properties associated with the antiferroelectric transition are interpreted in terms of a phenomenological theory.