Enhanced energy-storage performance of sol-gel BaZr0.25Ti0.75O3 thin films via phase evolution of amorphous-crystalline structure

Eco-friendly dielectric thin-film capacitors with high-performance energy-storage properties have been widely used in modern electronic devices. Herein, lead-free BaZr0.25Ti0.75O3 thin films were fabricated using the sol-gel spin-coating method. The phase evolution from amorphous to pyrochlore to perovskite crystalline, driven by increasing the annealing temperature, can be confirmed by high-resolution transmission-electron microscopy and x-ray diffraction. The results indicate that the thin films annealed at 600 °C have a high recoverable energy-storage density of 67.6 J/cm3 and an excellent energy efficiency of 94.5%, which were attributed to the existence of nano-scale polar regions (2–5 nm in size) inside a non-polar amorphous matrix. Simultaneously, the excellent stability of energy-storage properties over a wide temperature range of 25–200 °C, together with the strong fatigue-endurance after 109 cycles even at an elevated temperature of 200 °C, demonstrate that the designed thin films are promising for applications of pulse-power energy capacitors in a harsh environment.