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 Na0.5Bi0.5TiO3-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) (0.6Na0.5Bi0.5TiO3 - 0.4Sr0.7Bi0.2TiO3) - xBa(Mg1/3Ta2/3)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 (Wrec = 8.58 J/cm3, η = 93.5%) were obtained simultaneously under 565 kV/cm for the BNST-0.08BMT ceramic. The introduction of Sr0.7Bi0.2TiO3 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 (Wd = 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.
Keywords: Bi0.5Na0.5TiO3; Mg/Ta modification; composition design; energy storage ceramics; environmentally friendly.