Simultaneously achieved high energy density and excellent thermal stability of lead-free barium titanate-based relaxor ferroelectric under low electric field

Dielectric capacitors with high power density and excellent temperature stability are highly demanded in pulsed power systems. BaTiO₃-based lead-free relaxor ceramics have been proven to be a promising candidate for energy storage applications. However, the presence of low maximum polarization (P_max) heavily restricts its applications in the energy storage field. In order to significantly increase P_max under low electric field, a strategy, via introducing Bi_0.5Na_0.5TiO₃ (BNT) and Ca²⁺, constructing local compositional disorder and decreasing grain size, is propounded in this work. High P_max of 42.11 µC cm⁻² and large breakdown electric field (E_b) of 210 kV cm⁻¹ were attained in Bi_0.5Na_0.5TiO₃-modified BT-based solution, giving rise to ultrahigh W_rec of 2.57 J/cm³. The significantly improved W_rec is much superior to the previous other lead-free dielectric ceramic under moderate electric fields (< 220 kV cm⁻¹). In addition, an excellent temperature stability (the variation of W_rec is less than 3% in the temperature range of 20–120 °C) was obtained in this BNT-modified BT-based bulk materials. These results demonstrate that the strategy is practicable and effective to hike the energy density up for BaTiO₃-based bulk ceramics, which may pave a significant step towards utilizing energy storage applications for BaTiO₃-based materials.