Improved energy storage performance at the phase boundary in BaTiO₃-based film capacitors

Relaxor ferroelectric films have been widely studied for applications in miniaturized advanced pulsed power devices due to their fast charging and discharging rates and very fine polarized electric field hysteresis, which can be designed by incorporating paraelectric components into the ferroelectrics. In this work, lead-free BaTiO₃-based relaxor ferroelectric films are achieved by formulating solid solutions of ferroelectric BaTiO₃ with the paraelectric BaZrO₃. The optimized energy storage performance is achieved at the ferroelectric-relaxor ferroelectric phase boundary in the BaZr_0.3Ti_0.7O₃ films with an improved recoverable energy storage density of 58.6 J/cm³ and an energy storage efficiency of 71 % at 3600 kV/cm due to the increased maximum polarization. In addition, frequency-insensitive stability from 100 Hz to 10 kHz, long-term fatigue resistance up to 10⁷ switching cycles, and high-temperature stability in the range of 20 °C–100 °C are achieved. The work offers a good strategy via creating a phase boundary for improving the energy storage performance in the BaTiO₃-based relaxor ferroelectric films for advanced energy storage dielectric capacitors.