Excellent energy storage performance in multiple aliovalent B-site ions modified Bi_0.5Na_0.5TiO₃ high entropy relaxor ferroelectrics

The Bi_0.5Na_0.5TiO₃-based lead-free ceramics demonstrate significant potential as energy storage dielectric materials owing to their high polarization and satisfactory compatibility of multiple elements. In this study, multi-aliovalent B-site ions doped (Na_0.2Bi_0.2Ba_0.2Sr_0.2Ca_0.2)TiO₃ (NBBSCT) high entropy ceramics were prepared to enhance energy storage performance. The introduction of (Mg_1/3Nb_2/3)⁴⁺ (MN) dopants significantly increased configurational entropy, thereby promoting ionic disorder. Consequently, a high recoverable energy storage density (W_rec) of 7.1 J/cm³ and an ultrahigh energy storage efficiency (η) of 93% were simultaneously realized in 3% MN modified NBBSCT ceramics under 610 kV/cm, accompanied by good charge-discharge performance. The enhanced performance was attributed to the improved relaxor feature enabled by the high entropy strategy. Moreover, the ceramics exhibited outstanding frequency stability with a minimal variation of less than 3% over a broad range of 1 Hz to 200 Hz and good temperature stability with variation less than 10% from room temperature to 120 ℃ in W_rec. These results confirm that the high entropy strategy combined with multi-aliovalent B-site doping provides an effective approach to achieving superior energy storage performance in Bi_0.5Na_0.5TiO₃-based relaxor ferroelectrics.