Enhanced Energy Storage Performance of Lead-Free Capacitor in Ultra-widen Temperature range via Engineering Paraferroelectric and Relaxor Ferroelectric Multilayer Film.

Industry has been seeking the thin film capacitor that can work at high temperature in harsh environment, where the cooling systems are not desired. Up to now, the working temperature of thin film capacitor is still limited up to 200 °C. Herein, we design a multilayer structure with layers of paraferroelectric (Ba0.3Sr0.7TiO3, BST) and relaxor ferroelectric (0.85BaTiO3-0.15Bi(Mg0.5Zr0.5)O3, BT-BMZ) to realize optimum properties with a flat platform of dielectric constant and high breakdown strength for excellent energy storage performance at high temperature. Through optimizing the multilayer structure, a highly stable relaxor ferroelectric state is obtained for the BST/BT-BMZ multilayer thin film capacitor with a total thickness of 230 nm, a period number N=8, and a layer thickness ratio of BST/BT-BMZ=3/7. The optimized multilayer film shows significantly improved energy storage density (up to 30.64 J/cm3) and energy storage efficiency (over 70.93%) in ultra-wide temperature range from room temperature to 250 °C. Moreover, the multilayer system exhibits also excellent thermal stability in such ultra-wide temperature range with the change of 5.15%, and 12.75% for the recoverable energy density and energy storage efficiency, respectively. Our results demonstrate that the designed thin film capacitor is promising for the application in harsh environment and open a way to tailor thin film capacitor toward higher working temperature with enhanced energy storage performance.