Giant electrostrains accompanying the evolution of a relaxor behavior in Bi(Mg,Ti)O3–PbZrO3–PbTiO3 ferroelectric ceramics

Extremely enhanced electrostrains (up to 0.39%) were surprisingly observed in (0.67 − x)Bi(Mg0.5Ti0.5)O3–xPbZrO3–0.33PbTiO3 (BMT–xPZ–PT) ternary solid solutions, possibly resulting in BMT–xPZ–PT ceramics having great potential for large-displacement actuator applications. The generation of giant strains was found to be closely associated with the evolution of a weak relaxor behavior from diffuse-type BMT–PT binary ferroelectrics, during which the domain switching is actively facilitated owing to a change in the dynamics of the polar nanoregions from a static state to a dynamic state. It can be also attributed to a ferroelectric nature of the evolved relaxors in PZ substituted BMT–PT ceramics instead of a dipole glass freezing state. These judgements were reasonably supported by a couple of measurements, including strains vs. electric field, Raman scattering, dielectric spectroscopy and the time- and electric-field-dependent polarization. The present study can provide a general approach towards an appropriate compositional design for large electrostrains in BMT-based and related systems.