Enhanced energy storage performances of CaTiO3-based ceramic through A-site Sm3+ doping and A-site vacancy

•Ca1-1.5xSmx□0.5xTiO3 ceramics designed in terms of A-site donor Sm3+ and A-site vacancy (VA) were prepared by a solid state reaction method.•A-site donor Sm3+ and A-site vacancy (VA) strategy results in the greatly enhanced dielectric breakdown strength.•Ca1-1.5xSmx□0.5xTiO3 ceramics present the linear dielectric feature with significantly decreased dielectric loss.•High energy storage density (U = 2.0 J/cm3) and energy efficiency (η = 93.7 %) are achieved.