Mechanical activation-induced sequential combination, morphotric segregation and order–disorder transformation in Pb-based relaxors

Abstract

Having explored mechanical activation for synthesis and fabrication of Pb-based relaxor ferroelectrics, we observed several unique phenomena in association with mechanical activation of these electroceramic materials, including the unique nanocrystalline structure, phase transition, order–disorder transformation and activation-induced morphotropic behavior. In the study of sequential combination of Pb(Fe 1/2Nb 1/2)O 3 (PFN), nanocrystallite perovskite PFN phase is successfully derived from mechanical activation of both mixed oxides and Columbite precursor. However, the two nanocrystalline PFN phases are considerably different in phase stability. Mechanical activation can lead to morphotropic behavior in complex perosvkites, such as in Pb(Ni 0.5W 0.5)O 3–PbTiO 3 (PNW–PT), where an unique temperature-stable dielectric behavior is demonstrated over the wide temperature range of −120 to 40 °C. Both short range disordering and long range disordering occur in Pb(Mg 1/3Nb 2/3)O 3–Pb(Mg 1/2W 1/2)O 3 (PMN–PMW) upon mechanical activation. A Monte-Carlo simulation algorithm, based on the competition between the thermal activation and the mechanical activation-triggered shear process, is established to model the order–disorder transformation in Pb-based relaxor ferroelectrics.