Temperature-insensitive large electrostrains and electric field induced intermediate phases in (0.7 − x)Bi(Mg1/2Ti1/2)O3–xPb(Mg1/3Nb2/3)O3–0.3PbTiO3 ceramics

Large electrostrains (∼0.4% at 7 kV/mm) of the new (0.7 − x)Bi(Mg1/2Ti1/2)O3–xPb(Mg1/3Nb2/3)O3–0.3PbTiO3 ((0.7 − x)BMT–xPMN–0.3PT) ceramics with x = 0.0–0.7 near the morphotropic phase boundary of the BMT–PT–PMN ternary system were found to be associated with the evolution of the compositionally modulated dielectric relaxor behavior. As disclosed by in situ high-resolution synchrotron X-ray diffraction, more intermediate phases of different symmetries induced by external fields largely contribute to smaller strain hysteresis (∼23%) of PMN-rich compositions than BMT-rich ones. Particularly, the x = 0.2 sample exhibits temperature-insensitive electrostrains of ∼0.3% at 5 kV/mm varying less than 10% from room temperature up to 160 °C, which is mainly attributed to the coexistence of two kinds of relaxor states in a broad temperature range owing to special static domain structures typical for BMT-rich compositions. These findings provide a new approach toward an appropriate compositional design for low-hysteresis temperature-insensitive large electrostrains in BMT-based relaxor ferroelectrics.