Large Energy Density, Excellent Thermal Stability, and High Cycling Endurance of Lead-Free BaZr_0.2Ti_0.8O₃ Film Capacitors

A large energy storage density (ESD) of 30.4 J/cm³ and high energy efficiency of 81.7% under an electrical field of 3 MV/cm was achieved at room temperature by the fabrication of environmentally friendly lead-free BaZr_0.2Ti_0.8O₃ epitaxial thin films on Nb-doped SrTiO₃ (001) substrates by using a radio-frequency magnetron sputtering system. Moreover, the BZT film capacitors exhibit great thermal stability of the ESD from 16.8 J/cm³ to 14.0 J/cm³ with efficiency of beyond 67.4% and high fatigue endurance (up to 10⁶ cycles) in a wide temperature range from room temperature to 125 °C. Compared to other BaTiO₃-based energy storage capacitor materials and even Pb-based systems, BaZr_0.2Ti_0.8O₃ thin film capacitors show either high ESD or great energy efficiency. All of these excellent results revealed that the BaZr_0.2Ti_0.8O₃ film capacitors have huge potential in the application of modern electronics, such as locomotive and pulse power, in harsh working environments.