Ultrahigh Energy Storage Density and Efficiency in Bi_0.5Na_0.5TiO₃-Based Ceramics via the Domain and Bandgap...

Environmentally friendly lead-free dielectric ceramics have attracted wide attention because of their outstanding power density, rapid charge/dischargerate, and superior stability. Nevertheless, as a hot material in dielectric ceramic capacitors, the energy storage performance of Na_0.5Bi_0.5TiO₃-based ceramics has been not satisfactory because of their higher remnant polarization value and low dielectric breakdown strength, which is a problem that must be urgently overcome. In this work, the (1 - x) (0.6Na_0.5Bi_0.5TiO₃ - 0.4Sr_0.7Bi_0.2TiO₃) - xBa(Mg_1/3Ta_2/3)O₃ (BNST-xBMT) systems were designed based on a dual optimization strategy of domain and bandgap to solve the above problems. As a result, a record-breaking ultrahigh energy density and excellent efficiency (W_rec = 8.58 J/cm³, η = 93.5%) were obtained simultaneously under 565 kV/cm for the BNST-0.08BMT ceramic. The introduction of Sr_0.7Bi_0.2TiO₃ induces the formation of nanodomains in BNT-based ceramics, leading to slim P-E curves, and the further modification of Mg/Ta reduces the grain sizes and increases the bandgap width, resulting in significant enhancement of the dielectric breakdown strength. Moreover, excellent stability and superior discharge performance (W_d = 4.7 J/cm³, E = 320 kV/cm) in the BNST-0.08BMT ceramic were also achieved. The results suggest that the BNST-0.08BMT ceramic shows potential applicability for dielectric energy storage ceramics. Simultaneously, the composition-design concept in the system provides a good reference for the further development of ceramic dielectric capacitors.