Enhanced energy storage properties of (Ba_0.4Sr_0.6)TiO₃ ceramics with ultrahigh energy efficiency through doping of Bi_0.2Sr_0.7(Mg_1/3Nb_2/3)O₃

Dielectric (Ba_0.4Sr_0.6)TiO₃ (BST) ceramics are promising dielectric energy storage materials due to their moderate dielectric constant, low dielectric loss, and slight nonlinearity. However, their energy density is limited by their low breakdown strength (BDS). In this study, we aimed to address this limitation by incorporating various amounts of Bi_0.2Sr_0.7(Mg_1/3Nb_2/3)O₃ (SBMN) into the BST matrix. The (1–x)BSTxSBMN ceramics were prepared by conventional solid-state sintering, resulting in single-phase solid solutions. Compared to pure BST ceramics, the (1–x)BST–xSBMN ceramics exhibited lower remnant polarization and significantly enhanced BDS. Furthermore, the relaxation of the ceramics enhanced with increasing doping concentration, with an efficiency of η = 94.0% achieved at x = 0.20. Among them, the breakdown field strength of 0.85BST–0.15SBMN ceramics was 597 kV cm⁻¹, achieving a recoverable energy storage density of W_rec = 2.81 J cm⁻³ and an efficiency of η = 90.8% under an external electric field of 480 kV cm⁻¹. Subsequent tests revealed that the introduction of SBMN not only increased the band gap and conduction activation energy of the material, leading to an increase in BDS, but also promoted the formation of polar nanoregions (PNRs) which contributed to boosted energy efficiency, resulting in a significant enhancement in the energy storage performance of BST ceramics.