Fine-grain induced outstanding energy storage performance in novel Bi0.5K0.5TiO3–Ba(Mg1/3Nb2/3)O3 ceramics via a hot-pressing strategy

Abstract

Currently, bismuth-based perovskite-type ceramics are considered as promising species in energy storage applications because of easy phase- and micro/macro-structure modulations and high performances. In this work, the composition dependent phase structure and ferroelectric properties of novel Bi_0.5K_0.5TiO₃–Ba(Mg_1/3Nb_2/3)O₃ (BKT–BMN) ceramics are studied. Relaxor properties are gradually enhanced with increasing BMN content. The BKT–0.15BMN composition is selected to further explore energy storage performance via the hot-pressing (HP) technique. The results show that the recoverable energy storage density (W_R = 3.14 J cm⁻³) for the HP sample is more than two times larger than that of the conventional sintering (CS) one. The outstanding W_R also exhibits super stability against temperature and frequency variations. Besides, the energy storage efficiency (η) is up to 83.7% for the HP sample. In particular, the stored energy can be released in a very short time of ∼0.12 μs at room temperature, indicating a fast discharging speed for the HP sample. The enhanced performance is due to the decrease of grain size and the increase of grain boundaries, the mechanism underlying the microstructure effect on the breakdown strength (BDS) value is disclosed by numerical simulations (COMSOL). This work not only enriches the bismuth-based ceramic systems in pulsed power applications, but also deepens the understanding of the intrinsic mechanism of a refined microstructure that boosts energy storage performance.