High energy storage efficiency and thermal stability of A-site-deficient and 110-textured BaTiO₃–BiScO₃ thin films

The development of thin film dielectrics having both high energy density and energy conversion efficiency, as well as good thermal stability, is necessary for practical application in high-temperature power electronics. In addition, there is a demand for the development of new Pb-free high-energy density dielectric materials due to environmental concerns. In this regard, thin films of weakly coupled relaxors based on solid solutions of BaTiO₃–BiMeO₃ have shown good promise, because they exhibit a remarkably large polarization over a wide temperature range. Nevertheless, the performance of Pb-free thin films has lagged behind that of their Pb-based counterparts in terms of thermal stability and energy conversion efficiency. Toward this end, most recent studies on BaTiO₃–BiMeO₃ systems have focused on the optimization of material composition, while relatively less attention has been paid to other aspects such as defect chemistry and crystallographic texture. In this study, we examine the effects of A-site vacancy and crystallographic texture on the energy storage performance of BaTiO₃–BiScO₃ thin films synthesized using pulsed laser deposition (PLD). It is shown that a high energy storage density (W_r) of ~28.8 J/cm³ and a high efficiency of η >90% are achieved through a combination of moderate A-site vacancy concentration and (110) crystallographic texture. Furthermore, W_r remains nearly temperature independent while a high efficiency of η >80% is maintained for temperatures up to 200°C, which constitutes one of the best performances for Pb-free ferroelectric films for high-temperature capacitor applications.