Transformation of Ba_0.7Sr_0.3TiO₃ from ferroelectrics to relaxor ferroelectrics by doping of Bi(Mg_0.5Sn_0.5) and realization of high energy storage

The relaxor ferroelectrics as a new type of lead-free capacitor ceramic with high energy storage density has been extensively explored. In this paper, we reported a new recipe, (1−x)Ba_0.7Sr_0.3TiO₃–xBi(Mg_0.5Sn_0.5)O₃, known as (1−x)BST–xBMS. The samples were prepared by conventional solid-state reaction method with varying x (x = 0.00, 0.04, 0.08, 0.12, 0.16, 0.20). The dependence of phase structure, dielectric and energy storage performances on varying amount of BMS were systematically investigated. The results prove that the introduction of BMS alter the structure of the oxygen octahedron (B-O₆), disturb the long-range ordering of dipoles, and produce numerous polar nanoregions (PNRs), made the (1−x)BST–xBMS ceramic transforms from ferroelectrics to relaxor ferroelectrics. In particular, the 0.84BST–0.16BMS ceramic demonstrates a significant energy storage density (W_rec = 0.73 J/cm³) and energy storage efficiency (ŋ = 87.2%) when subjected to an applied electric field of 170 kV/cm. At 160 kV/cm, the ceramic displays high power density (P_D = 11.02 MW/cm³), current density (C_D = 137.79 A/cm²), and an extremely shot discharge time (t_0.9 = 50 ns). Additionally, it also exhibits good temperature stability (20–180 °C), frequency stability (40–200 Hz), and cycling stability (1–10⁶).