A supercritical relaxor phase boundary for ultrahigh electrostrictive properties

Electrostrictive materials have been actively studied for applications in precision machinery, laser communication, and biological microscopy due to their numerous advantages, including high resolution, negligible hysteresis, low heat dissipation, and fast response. Nevertheless, simultaneously achieving high strain and low hysteresis in electrostrictive materials presents a great challenge, impeding the development of high precision positioning devices. In this study, we designed a critical phase point where the relaxor state coexists with the rhombohedral and tetragonal phases, offering a favorable environment for the reversible transition from the ergodic relaxor state to an unstable long-range ordered ferroelectric state under an external electric field, enabling a high electrostrictive strain. To achieve this strategy, we introduced a strong relaxor component by incorporating a Nd dopant into Pb(Mg1/3Nb3/2)O3-PbTiO3 (PMN-PT) ceramics, thereby enhancing local structural heterogeneity. The resulting 4%Nd-doped 0.69PMN-0.31PT ceramic exhibits an excellent electrostrictive strain of 0.22% with a highly effective piezoelectric strain coefficient Smax/Emax = 730 pm V-1 at 30 kV cm-1, superior to those of previously reported electrostrictive ceramics and most piezoelectric ceramics. Moreover, the 4%Nd-doped 0.69PMN-0.31PT ceramic demonstrates favorable temperature stability, maintaining an electrostrictive strain of 0.15% at temperatures up to 80 degrees C. This work provides an effective way to obtain high-performance electrostrictive materials via synergistically enhancing local structural heterogeneity and designing a morphotropic relaxor phase boundary. In this work the design of a critical phase point where reversible transition from the ergodic relaxor state to an unstable long-range ordered ferroelectric state takes place is reported.