High energy storage and thermal stability under low electric field in Bi_0.5Na_0.5TiO₃-modified BaTiO₃-Bi(Zn_0.25Ta_0.5)O₃ ceramics

Dielectric energy storage capacitors have been comprehensively investigated for application in advanced electronic systems. Compared to other types of ceramic capacitors, BaTiO₃-BiMeO₃ lead-free composite relaxor ferroelectric ceramics (where Me represents trivalent or trivalent composite ion) are excellent dielectric energy storage candidates in pulsed power fields. However, the properties of most existing BT-based energy storage ceramics are not satisfactory in some practical aspects, and feasible guidance on efficient composting material systems with large recoverable energy storage density (W_rec) for ultralow electric fields is lacking. Herein, for the first time, lead-free relaxor ferroelectric (1-x)[0.9BaTiO₃-0.1Bi(Zn_0.25Ta_0.5)O₃]-xBi_0.5Na_0.5TiO₃ ceramics with x = 0, 0.1, 0.2, 0.3, and 0.4 were synthesized via composite strategy using the traditional solid-state process. The used strategy combined the complementary advantages of both BT-BZT and BNT to greatly increase the saturation polarization (P_s) and shift the stable temperature range of permittivity to high-temperature region, achieving higher energy storage density and improved temperature stability. Optimum energy storage performances with a high W_rec of 4.18 J/cm³ and comparatively high η of 84.01% were simultaneously achieved in the relatively low electric field of 230 kV/cm. Moreover, the ceramic obtained at x = 0.3 showed excellent temperature stability with the change rate of W_rec < 5% and η < 6% throughout a broad temperature range (20 °C ∼ 170 °C). This ceramic (x = 0.3) simultaneously possesses superior pulse performance, exhibiting the t_0.9 of 232 ns and W_dis of 2.51 J/cm³. Overall, the employed composite strategy design is effective for obtaining energy storage capacitors with excellent performance for future advanced pulsed power devices.