Achieving ultrahigh energy storage density under low electric field in (Na0.5Bi0.5)TiO3-based relaxor ferroelectric ceramics via a synergistic optimization strategy

Abstract

Lead-free dielectric ceramic capacitors are attracting much interest in pulse power systems owing to their fast charge/discharge rate and high power density. However, their development towards integration and miniaturization in electronic devices has been severely impeded by low energy storage performance (ESP) under low electric field (E). Herein, a synergistic optimization strategy of composition design and domain engineering was proposed in the Bi(Mg0.5Hf0.5)O3-modified Na0.5Bi0.5TiO3-Sr0.7Bi0.2Ca0.1TiO3 ceramics [(1-x)(NBT-SBCT)-xBMH], aiming to improve ESP at low E. As a result, an ultrahigh recoverable energy density (Wrec) of ∼5.9 J/cm3 and a high efficiency (η) of ∼85 % can be obtained in x = 0.20 ceramics under a low E of 260 kV/cm, which is superior to previously reported lead-free materials under the equivalent E. The outstanding Wrec is mainly ascribed to the ultrahigh polarization discrepancy (ΔP) of ∼50.8 μC/cm2 since the rich hybridization of Bi 6 s and O 2p orbitals maintains a maximum polarization and the addition of Mg2+ and Hf4+ transforms the long-range ferroelectric order into polar nanoregions (PNRs) with good relaxation characteristics. Moreover, a fast discharge time (∼62 ns), good temperature (20–120 °C) and frequency (1–103 Hz) stabilities, and excellent fatigue resistance (×105 cycles) can be concurrently realized in x = 0.20 ceramics. These results demonstrate the promising strategy of developing low E lead-free ceramics for dielectric energy storage.