Tunability properties in the paraelectric state of the Pb(Mg1/3Nb2/3)O-3 ceramics

Pb(Mg1/3Nb2/3)O-3 ceramics prepared via columbite method exhibit high crystallinity and high density after sintering at 1200 degrees C. Typical relaxor behavior are demonstrated by the dielectric data. Although showing a diffuse phase transition, at room temperature the system is in its paraelectric state, i.e. the PMN structure is fully cubic. The dc-tunability was investigated above the room temperature, when other field-induced contributions than ferroelectric polarization might cause non-linearity. A random non-interacting dipolar unit in a double well potential was employed to describe the epsilon(E) non-linearity. The temperature-dependence of the average polarization corresponding to the polar nanoregions in the paraelectric state of the PMN relaxor was calculated from the epsilon(E) data at various temperatures above T-m. A similar trend of decreasing as increasing temperature shows the spin-glass local order parameter determined from the dielectric constant data in the paraelectric state. The local order parameter in the paraelectric state is determined by the nanopolar domains size and correlations. (C) 2009 Elsevier Ltd. All rights reserved.