Nanocrystalline Engineering Induced High Energy Storage Performances of Fatigue-Free Ba2Bi3.9Pr0.1Ti5O18 Ferroelectric Thin Films

Electrostatic capacitors, though presenting faster rate capability and higher power density, are hindered in applications because of their low energy density. Accordingly, many efforts in electrostatic capacitors, for electronics and electrical power systems, have mainly concentrated on the development of dielectric materials with high-energy density (U_d) and charge-discharge efficiency (η) as well as good stability performances of thermal and fatigue endurance. Herein, we demonstrate that an excellent U_d (∼90 J/cm³) and high η (∼84.2%), as well as outstanding fatigue cycles (1 × 10⁸ st), frequency stability (20-2000 Hz), and a wide temperature range (RT ∼ 160 °C), can be attained in Ba₂Bi_3.9Pr_0.1Ti₅O₁₈ (BBPT) ferroelectric thin films via nanocrystalline engineering. It is revealed that nanocrystalline engineering of the BBPT ferroelectric thin films could be controlled via the heat-treatment temperature, which could effectively regulate the breakdown strength and polarization. The enhanced breakdown strength and polarization of the nanocrystalline engineering is further verified through the theoretical phase-field simulations along with experimental results. These results indicate that this is a feasible and scalable route to develop dielectric thin film materials with a high energy storage capability.