Enhanced energy storage performance of Sr0.7Bi0.2TiO3@ NaNb0.9Ta0.1O3 relaxor ferroelectrics via a synergistic optimization strategy

Sr_0.7Bi_0.2TiO₃-based ceramics with excellent dielectric temperature stability and energy storage efficiency (η) are expected to be applied in dielectric ceramic capacitors. Unfortunately, low breakdown strength (BDS) limits its application. In this work, the new Sr_0.7Bi_0.2TiO₃@xNaNb_0.9Ta_0.1O₃ (x = 5–20 mol%, SBT@xNNT) relaxor ferroelectric ceramics with fine grains were prepared by a two-step sintering process. The introduction of NNT causes the coexistence of multiphase in ceramics, which enhances the relaxation behavior and the temperature stability of energy storage. Meanwhile, the design of core–shell structure also improves the temperature stability of the ceramics. Thus, the energy density (W_rec) of 2.2 J/cm³ and η of 76% are achieved in Sr_0.7Bi_0.2TiO₃@xNaNb_0.9Ta_0.1O₃ ceramics at 249 kV/cm, and W_rec exhibits good temperature stability from 20 to 150 °C. The Sr_0.7Bi_0.2TiO₃@xNaNb_0.9Ta_0.1O₃ ceramics have excellent dielectric temperature stability (|Δε/ε_{20 °C}|≤ 15%) at  − 60–120 °C. The as-prepared SBT@10NNT ceramics are suitable for the application in dielectric ceramic capacitors. This study provides SBT-based ceramics for a novel strategy for optimizing the energy storage performance.