Evaluation of ion conductivity of ZrO2 thin films prepared by reactive sputtering in O2, H2O, and H2OÂ +Â H2O2 mixed gas

► Hydrated ZrO2 thin films were prepared by reactive sputtering. ► O2, H2O, and H2O + H2O2 mixed gas were used as reactive gases. ► High ion conductivities of 2-3 × 10-8 S/cm were obtained using H2O and H2O + H2O2. ► However, the ion conductivity of the films deposited in O2 was poor. ► Low density and high water content of the films caused the high ion conductivity.