| Nanocrystalline Gd2O3 doped CeO2 (abbreviated as GDC) ion conductor electrolyte thinfilms, synthesized by reactive magnetron sputtering on (0001) sapphire substrates, have beencharacterized by XRD, AFM and AC impedance analysis. The results show that, the f.c.cstructured GDC films have strong (111) textures when synthesized at different substratetemperatures (300-700℃), while the surface morphologies and roughness vary with the substratetemperature. The film grown at temperatures of 300℃is characterized by prismatic islands inlayer growth mode; Those grown at temperatures of higher than 400℃are covered with dense,small round growth islands; At the temperature of 400℃, however, large prismatic islands aredispersively developed among dense, small round islands. This morphology change characteristicof different nucleation mechanisms at the beginning of film growth is probably due totransformation of the surface structure of the (0001) sapphire at different temperatures. The ACimpedance complex plane plot of the GDC film is mainly contributed by grain boundaryresistances. The conductivity activation energy (1.2～1.5eV) calculated by the Arrhenius plot isclose to the reported value for the grain boundary conductivity and decreases with highersubstrate temperature (Ea300＞Ea400＞Ea600). Difference in activation energy and grain sizes betweenGDC films synthesized at temperatures of 300℃, 400℃and 600℃causes different dependenceof film conductivity on the temperature.
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