Defect dipole induced large recoverable strain and high energy-storage density in lead-free Na_0.5Bi_0.5TiO₃-based systems

In this letter, we propose an effective route to obtain large recoverable strain, purely electrostrictive effects and high energy-storage density by inducing defect dipoles into Na_0.5Bi_0.5TiO₃ (NBT)-based relaxor ferroelectrics. It has been found that pinched and double polarization hysteresis loops with high maximum polarization (P_max) and negligible remanent polarization (P_r) can be observed due to the presence of acceptor-induced defect dipoles. A large recoverable strain of 0.24% with very little hysteresis and high electrostriction coefficient of 0.022 m⁴C² with purely electrostrictive characteristics were acquired when 11 mol. ‰ Mn-doped. Meanwhile, a high recoverable energy density of 1.06 J/cm³ with excellent temperature stability was obtained at the same composition owing to the enlarged value of P_max-P_r (36.8 μC/cm²) and relatively high electric field (95 kV/cm). Our achievement can open up the exciting opportunities for ferroelectric materials in high-precision positioning devices and high electric power pulse energy storage applications.