Giant energy storage efficiency and low strain hysteresis in lead-free relaxor ferroelectrics by designing the dynamic behavior of PNRs

Lead-free ferroelectric ceramics have aroused widespread concerns, due to their properties of rapid charge/discharge and electric-induced strain without harming the environment. However, compared with thin-film capacitors, ceramics have a larger energy loss. In addition, the large time lag between electric field and strain also reduces its accuracy as an actuator. Therefore, the relaxor ternary solid solution (BaTiO₃–Bi_0.48Na_0.48La_0.03TiO₃–NaNbO₃) was constructed in this work, aiming to obtain large energy storage efficiency and low time delay. The strategy and optimization aim to improve the relaxation degree and reduce the maximum permittivity temperature to room temperature, building a special crossover region where high and low dynamic polar nano regions co-existence. Thus a recoverable energy density of 1.24 J/cm³ under a low electric field (135 kV/cm) and a high energy storage efficiency (96%) are obtained and low hysteresis electrostriction with a large electrostriction coefficient (Q₃₃ = 0.0367 m⁴/C²) is also achieved in this system. This work suggests that this system can be considered promising materials as high-efficiency capacitors and high-precision actuators. It also attracts interest in the basic research on the dynamic changes of polar nano regions.