Effect of Hf concentration on energy storage performance of lead-free BaHf _xTi_{1- x}O₃thin film capacitors

Dielectric capacitors have received extensive attention on account of their ultrahigh power density. In this paper, we successfully prepared Ba (HfxTi1-x) O3 (x = 0.05, 0.11, and 0.25) thin films on the (001) Nb-doped SrTiO3 substrates through a radio-frequency magnetron sputtering, and the leakage characteristics and energy storage properties of these films were investigated. X-ray diffraction analysis demonstrates that all films are epitaxial. The leakage current decrease as x increases, which indicates that the introduction of Hf can effectively suppress the dielectric loss and enhance the breakdown strength. In the meanwhile, when x = 0.25, the maximal energy storage density with 64.0 J/cm3 and the excellent breakdown strength with 6.07 MV/cm are obtained. Likewise, the improved breakdown strength induces outstanding high temperature resistance in the wide temperature range of -100 to 200 °C, and the energy storage density and energy storage efficiency remain the value of 35.5 J/cm3 and 72.72% at 4 MV/cm in this temperature range. These results imply that Hf substitution is a feasible and operative way to improve energy storage performance of the film and provide feasibility for the future research of BaHfxTi1-xO3 series films.