Stronger B-site ionic disorder boosting enhanced dielectric energy-storage performance in BNT-based relaxor ferroelectric ceramics

Because of their possible applications in dielectric energy-storage capacitor devices, (Bi_0.5Na_0.5)TiO₃-based (BNT) relaxor ferroelectric (RFE) ceramics are feasible alternatives to lead-containing electroceramics. Good energy-storage performance (ESP), including high recoverable energy density (W_rec) and good energy discharge efficiency (η), is required to achieve device miniaturization and long device lifetimes. An advanced method was used to overcome the challenges of A-site ionic disordered RFE in achieving high inducible polarization and low hysteresis, with the former dictating a large W_rec and the latter dictating a high η. In this study, an ABO₃ perovskite-structured complex end-member Bi(Mg_2/3Nb_1/3)O₃ (BMN) was added to a 0.7Bi_0.5Na_0.4K_0.1TiO₃–0.3Ba_0.5Sr_0.5TiO₃ (0.7BNKT–0.3BST) matrix. The differences in the valence states and ionic radii of Mg²⁺, Ti⁴⁺, and Nb⁵⁺ increased the local electric field fluctuation, which contributed to the expanded dielectric relaxation properties. The combined substantial prevention of hysteresis and remanent polarization suggests high potential applicability for ESP. Finally, an enhancement in W_rec to 4.98 J/cm³ was achieved in 0.595BNKT–0.255BST–0.15BMN with an ultrahigh η of 97.3% in a medium-strength electric field of 300 kV/cm. The ESP also demonstrated good thermostability between 30 and 120 °C. Furthermore, the strategy used in this study to generate RFEs can serve as a guide for future research.