(Bi_0.5Na_0.5)TiO₃-based relaxor ferroelectrics with enhanced energy-storage density and efficiency under low/moderate - fields via average ionic polarizability design

Electrostatic capacitors are promising candidates in the application of pulse-power systems due to their high power density and fast charge-discharge rate. However, the insufficient recoverable energy density (W_rec) and energy efficiency (η) under low/moderate electric field is still the bottleneck for their applications in miniaturized equipment and portable devices. In this work, we utilize an average ionic polarizability design strategy to enhance W_rec by sustaining the high-polarization gene of the system and simultaneously improve η by disrupting the polar order in (1-x)[0.7Bi_0.5Na_0.5TiO₃-0.3Sr_0.7Bi_0.2TiO₃]-xSr(Zn_1/3(Nb_0.85Ta_0.15)_2/3)O₃ ceramics. As a result, excellent energy-storage properties have been achieved both in low-field (W_rec ∼ 2.7 J/cm³ and high η ∼ 93% at 200 kV/cm) and moderate-field (W_rec ∼ 5.2 J/cm³ and η ∼ 91% at 330 kV/cm) for x = 0.12 sample. Additionally, the x = 0.12 sample exhibits good thermal stability (−50 ∼ 200 ℃), frequency stability (0.5 ∼ 500 Hz) and cycle stability (10⁵ cycles). Hence, the current work may provide some novel perspectives for improving the W_rec and η of dielectric capacitors under low/moderate electric fields.