Superior Energy-Storage Performances under a Moderate Electric Field Achieved in Antiferroelectric-like Na0.5Bi0.5TiO3-Based Relaxor Ferroelectric Ceramics by a Synergistic Optimization Strategy

The progress of power systems and electronic devices promotes the development of lead-free dielectric energy-storage material. Particularly, Na_0.5Bi_0.5TiO₃-based ferroelectric ceramics featuring large spontaneous polarization as well as wide dielectric adjustability and stability are highly recognized as promising candidates. However, their large remanent polarization (P_r) and low electric breakdown strength (E_b) result in unsatisfactory recoverable energy density (W_rec) and/or energy conversion efficiency (η), severely restricting their energy-storage applications. Herein, an effective synergistic optimization strategy has been proposed to gain superior energy-storage performances. Interestingly, the antiferroelectric-like (AFE-like) (1 – x)(Na_0.3Bi_0.38Sr_0.28TiO₃)-xBi(Mg_0.5Zr_0.5)O₃ (x = 0.00, 0.05, 0.10, 0.15, and 0.20) relaxor ferroelectric (RFE) ceramics were constructed via the phase structure, the polar structure, and the defect dipole modulations. With Bi(Mg_0.5Zr_0.5)O₃ increasing, the slim and pinched polarization–electric field hysteresis (P–E) loops become remarkably similar to the double-like P–E loops characterized by AFEs. Meanwhile, the strengthened E_b and delayed polarization saturation were also realized due to the enlarged band gap, refined grain size, and reduced free energy barrier. Consequently, superior energy-storage performances were achieved in this work. Noticeably, a large W_rec of 5.00 J/cm³ and a high η of 90.09% were realized in 0.85(Na_0.3Bi_0.38Sr_0.28TiO₃)-0.15Bi(Mg_0.5Zr_0.5)O₃ RFE ceramics at a moderate electric field of 340 kV/cm. Additionally, excellent energy-storage and/or charge–discharge reliabilities in frequency (1–500 Hz), temperature (20–140 °C), and fatigue cycle (1–50,000) were confirmed. These satisfactory results not only indicate the promising prospects of 0.85(Na_0.3Bi_0.38Sr_0.28TiO₃)-0.15Bi(Mg_0.5Zr_0.5)O₃ RFE ceramics in the dielectric energy-storage field but also verify the effectiveness of the synergistic optimization strategy proposed in this work.