Hydrated ZrO2 thin films were prepared by reactive sputtering in O-2, H2O, and H2O + H2O2 mixed gas, and the effect of the sputtering atmosphere on ion conductivity of the films was investigated. The results showed that the films deposited in O-2 gas exhibited poor ion conductivity; however, the ion conductivities of the films deposited in the other two kinds of atmosphere were similar and 300-500 times higher than that of the films deposited in O-2 gas. It was indicated that the higher ion conductivity of the films was caused by lower film density and higher water content. (C) 2012 Elsevier B.V. All rights reserved.