Significantly improved energy storage stabilities in nanograined ferroelectric film capacitors with a reduced dielectric nonlinearity

For the development of high energy density ferroelectric film/multilayer capacitors, which have applications in electric power systems and advanced pulsed-discharge devices, a stable energy storage performance in a wide range of temperature, frequency and cycling times has become extremely important. Here, we propose an effective method to boost the energy storage stabilities of ferroelectric film capacitors through the use of a nanoengineered film structure with a reduced dielectric nonlinearity. We show in (Ba-0.95,Sr-0.05)(Zr-0.2,Ti-0.8)O-3 (BSZT) ferroelectric films that such an approach is facilitated by reducing the size of sputtered columnar nanograins via a synergetic effect between a low temperature deposition process and a buffer-layer technique. In comparison with the BSZT films sputtered at 500 C which are better ferroelectrics, the 400 C-sputtered BSZT films not only showed an improved energy storage density and efficiency, but also displayed a reduced dielectric nonlinearity in its polarization response. The latter has led to a significantly improved energy storage stability under a changing temperature (-175 oC 200 C) or frequency (1 Hz 20 kHz), or after a large amount of charge-discharge cycles (up to 2 x 10(9)).