(Bi0.5Na0.5)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 (Wrec) 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 Wrec by sustaining the high-polarization gene of the system and simultaneously improve η by disrupting the polar order in (1-x)[0.7Bi0.5Na0.5TiO3-0.3Sr0.7Bi0.2TiO3]-xSr(Zn1/3(Nb0.85Ta0.15)2/3)O3 ceramics. As a result, excellent energy-storage properties have been achieved both in low-field (Wrec ∼ 2.7 J/cm3 and high η ∼ 93% at 200 kV/cm) and moderate-field (Wrec ∼ 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 Wrec and η of dielectric capacitors under low/moderate electric fields.