Effects of Annealing Temperature and Ion Doping on Energy Storage Performance of Na0.5Bi0.5TiO3-Based Thin Films

Lead-free ferroelectric thin film capacitors offering superb power density and fast charge-discharge rates are ideal for energy storage applications. However, the trade-off relationship between polarization strength and breakdown strength significantly hinders the improvement of energy storage performance. In this work, relaxor-ferroelectric Na0.5Bi0.5TiO3 (NBT) thin films have been deposited on Pt/Ti/SiO2/Si substrate via sol-gel method. First, the energy storage performance of the films is optimized by adjusting the annealing temperature. It is found that the NBT film annealed at 650°C has both excellent breakdown strength and polarization strength. Then the influence of ion doping on the energy storage performance of NBT films has been studied. An excellent energy storage density of 42.1 J/cm3 and efficiency of 55.8% are simultaneously achieved in the 2% Mn-NBT thin film. Additionally, the energy storage performance remains stable within the temperature range of 25 to 180°C and frequency range of 500 to 5000 Hz. The energy storage performance of 2% Mn-NBT thin film did not decrease significantly after 107 electrical cycles. It is predicted that this work will advance the utilization of Na0.5Bi0.5TiO3-based film capacitors in energy storage systems.