The electrical conductivity of similar to 200 nm-thick gadolinium-doped ceria (GDC) thin films deposited at various substrate temperatures by radio-frequency sputtering was evaluated in a temperature range of 400 degrees C-550 degrees C as an electrolyte for solid oxide fuel cells operated at low temperatures. Morphological, chemical, and crystalline properties were discussed to determine the electrical conductivity; in particular, the electrical conductivity of GDC thin film deposited at 300 degrees C was appreciably lower than that of GDC thin film deposited at 150 degrees C. The columnar grain boundaries and the reduced ceria formed during the sputtering process are considered as the major factors leading to the measured results. (C) 2015 Elsevier B.V. All rights reserved.