Excellent energy storage performance of paraelectric Ba0.4Sr0.6TiO3 based ceramics through induction of polar nano-regions

Dielectric energy storage materials with congenitally high power densities and ultrafast discharge rates have been extensively studied for emergent applications. As a typical and traditional dielectric material, paraelectric Ba_0.4Sr_0.6TiO₃ (BST) ceramic exhibits a moderate dielectric constant (ε_r), low dielectric loss and slightly nonlinear P–E hysteresis. However, its energy storage density (W) is extremely low because of its low maximum polarisation (P_max) and weak breakdown strength (BDS). In this study, ferroelectric Na_0.5Bi_0.5TiO₃ (NBT) was introduced into paraelectric BST to enhance energy storage performance. The results show that the introduction of NBT induced polar nano-regions (PNRs) in the paraelectric matrix, resulting in a slim hysteresis loop with low remnant polarisation (P_r) and high P_max simultaneously. Furthermore, owing to a decrease in the oxygen vacancy concentration and an increase in the band gap energy, the BDS of the BST ceramic also significantly increased. As a consequence, a remarkable energy storage density (W_rec = 3.89 J/cm³) and a high energy storage efficiency (η = 83.8%) were realised in the 0.75Ba_0.4Sr_0.6TiO₃-0.25Bi_0.5Na_0.5TiO₃ (0.75BST–0.25NBT) ceramic under a practical electric field of 360 kV/cm. Moreover, the ceramic also exhibited an excellent current density (～1029.7 A/cm²) and ultrahigh power density (～128.7 MW/cm²). The attained energy storage performances indicate that the NBT-modified BST ceramics are promising materials for high energy storage capacitor applications field.