Excellent energy-storage performance in Bi_0.5Na_0.5TiO₃-based lead-free composite ceramics via introducing pyrochlore phase Sm₂Ti₂O₇

The comprehensive performance of ferroelectric ceramic materials is a significant factor limiting the practical application. In this work, a novel strategy of constructing diphase compounds is proposed to significantly enhance the energy storage properties of Bi_0.5Na_0.5TiO₃-based ceramics. A composite ceramic of pyrochlore phase Sm₂Ti₂O₇ modified perovskite phase Bi_0.5Na_0.5TiO₃ is successfully prepared and systematically studied. As the concentration of Sm₂Ti₂O₇ increases, the dielectric breakdown strength is greatly strengthened because of expanded band gap and shrunk grain size, and the relaxor behavior is enhanced due to the effect of linear character pyrochlore. As a result, the optimized composition demonstrates excellent energy storage properties including high recoverable energy storage density (W_rec) of 6.387 J/cm³ at 402 kV/cm, superior stability of temperature (<6% variation in − 120 ∼ 120 °C), frequency (∼4% variation in 5 ∼ 500 Hz) and cycling (∼2% variation within 10⁶ cycles). Besides, fast discharge behavior of t_0.9 ∼ 29.4 ns and high power density of 80.49 MW/cm³ at 200 kV/cm are also achieved. This study presents a novel strategy to enhance the performance of BNT-based materials through forming composite ceramic, which is anticipated to be a general method for other material systems as regards the design of advanced energy storage ceramics.