Optimized dielectric energy storage performance in ZnO-modified Bi0.5Na0.5TiO3-Sr0.7Bi0.2□0.1TiO3 ceramics with composite structure and element segregation

Abstract

In this work, ZnO is introduced into the 0.55Bi_0.5Na_0.5TiO₃-0.45Sr_0.7Bi_0.2□_0.1TiO₃ (BNT-SBT) to optimize the dielectric energy storage performance. ZnO is not only used as a sintering aid to decrease the sintering temperature and ceramic grain size, but also enhances the random fields and polar nanoregions activity in the ceramics by Zn²⁺ doping. Intriguingly, the ZnO-modified BNT-SBT ceramics present a 0–3 type composite structure containing the TiZn₂O₄ and Bi₂Ti₂O₇ linear dielectrics. Moreover, obvious element segregation is generated in the BNT-based matrix grains showing different Sr²⁺/(Bi³⁺, Na⁺) ratios and polarization magnitudes. The significant variations in composition distribution, grain and domain configurations cause the overall optimization of energy storage properties, reflected in the enhanced breakdown strength, delayed polarization saturation, and reduced polarization hysteresis. As a result, the optimized W_rec ∼ 5.84 J/cm³ and η ∼ 93 % at 40 kV/mm is obtained in the BNT-SBT-0.10ZnO ceramic, superior to that of the BNT-SBT ceramic (W_rec ∼ 3.35 J/cm³ and η ∼ 89 % at 28 kV/mm).