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 Ba0.4Sr0.6TiO3 (BST) ceramic exhibits a moderate dielectric constant (εr), low dielectric loss and slightly nonlinear P–E hysteresis. However, its energy storage density (W) is extremely low because of its low maximum polarisation (Pmax) and weak breakdown strength (BDS). In this study, ferroelectric Na0.5Bi0.5TiO3 (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 (Pr) and high Pmax 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 (Wrec = 3.89 J/cm3) and a high energy storage efficiency (η = 83.8%) were realised in the 0.75Ba0.4Sr0.6TiO3-0.25Bi0.5Na0.5TiO3 (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.