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The Y-doped BaCeO 3 (BaCe 0.90 Y 0.10 O 3-δ ) thin films have prepared on Al 2 O 3 (0001) substrates by RF magnetron sputtering. The thin films prepared at the substrate temperature of 300~500°C exhibits (002), (022) and (400) orientations. The thin film consists of grain with a diameter of 60~150 nm and smooth surface, although the grain size depends on substrate temperature. The prepared thin films were transparent. The electrical conductivity of the thin film exhibits thermal activation type behavior in H 2 O atmosphere of temperature region from 700 to 300°C. The activation energy (E A ) of the thin film estimated from the Arrhenius plot is 0.30~0.42 eV. The E A values of the thin films are lower than that of the bulk ceramics.

0.05 Y 0.10 O 3-δ : BCRY) thin film has been prepared on (0001) Al 2 O 3 substrate by RF magnetron sputtering. The BCRY thin film crystallized at 600°C exhibits a-and c-axes orientations. The electrical conductivity of BCRY thin film is higher than that of BaCe 0.90 Y 0.10 O 3-δ (BCY) thin film. The activation energy (E A ) of BCRY thin film is ~0.25 eV, which corresponds to half E A of BCY thin film, below 400°C. The conductivity depends on oxygen partial pressure. The Fermi level (E F ) of BCRY thin film shifts to the conduction band side, although the E F of BCY thin film locates at the valence band side. The above results indicate that the BCRY thin film occurs the electron-ion mixed conductions below 400°C.