20 mol% Gd-doped ceria (20GDC) films on poly-crystalline 8 mol% yttria-stabilized zirconia tapes (8YSZt) were rf-sputtered through a lab-made 20GDC oxide target and investigated with regard to the oxygen non-stoichiometry, chemical composition, and morphology of the films. The as-deposited 20GDC dense films with various oxidation states of Ce ions were obtained by the deposition conditions of 200 W. The interpretation of chemical states of cerium (Ce) in the as-deposited 20GDC films showed the mixing tetravalent (Ce4+)/trivalent (Ce3+) states of Ce4O7 phase. After the annealing process in air at 900 degrees C for 2 h, results of X-ray diffraction and Xray photoelectron spectroscopy showed that the fully oxidized 20GDC phase with a cubic fluorite structure was obtained. Columnar grain features of annealed films were examined normal to 200 of 8YSZ substrates by quantitative transmission electron microscopy techniques. The conductivity measurement results provided, that the sputtered-20GDC films on 8YSZ tape can be used as solid electrolytes for improved electrochemical performance in a solid oxide fuel cell system at the operation temperatures of 500-700 degrees C. (C) 2016 Elsevier B.V. All rights reserved.