Excellent energy-storage performance in Bi0.5Na0.5TiO3-based lead-free composite ceramics via introducing pyrochlore phase Sm2Ti2O7

•The composite ceramics Bi0.5Na0.5TiO3-Sm2Ti2O7 were successfully prepared.•Excellent electrical properties and stability are obtained in BNT-STO ceramics.•A new effective method to design high ESP ceramic materials is proposed. 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 Bi0.5Na0.5TiO3-based ceramics. A composite ceramic of pyrochlore phase Sm2Ti2O7 modified perovskite phase Bi0.5Na0.5TiO3 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 (Wrec) of 6.387 J/cm3 at 402 kV/cm, superior stability of temperature (