Critical state to achieve a giant electric field-induced strain with a low hysteresis in relaxor piezoelectric ceramics

Due to the extrinsic contribution of domain wall motions to electro-strains, the incompatibility of the large electro-strain with a low hysteresis in piezoelectric ceramics is a stumbling block for designing high-performance piezoelectrical actuators. Herein, we report a critical state in relaxor ferroelectric systems enables to enhance the electro-strain and to reduce the hysteresis simultaneously. A room temperature ergodic relaxor state dominated by nanodomains with different local symmetries can be obtained by introducing Bi(Zn_1/2Ti_1/2)TiO₃ into 0.73 Pb(Mg_1/3Nb_2/3)O₃-0.27PbTiO₃ matrix. Like the morphotropic phase boundary (MPB) in ferroelectrics, the coexistence of different local symmetries is capable of facilitating the transition from the ergodic relaxor state to the ferroelectric under the applied field due to the ease of polarization rotation, thereby leading to a giant electro-stain (0.24%) under an electric field of 50 kV/cm. Furthermore, the field-induced ferroelectric state with the long-range ferroelectric order can spontaneously reverse back to the initial ergodic relaxor state during unloading the electric field, which contributes to a low hysteresis (15.4%). The present work not only introduces a solid solution system with excellent electro-strain properties but also affords a guidance for manipulating the electro-strain behavior by modulating phase structures and domain configurations of piezoelectric ceramics.