Epitaxial thin films of GdBaCo2O5.5+δ (GBCO) grown by pulsed laser deposition have been studied as a function of deposition conditions. The variation in film structure, domain orientation, and microstructure upon deviations in the cation composition have been correlated with the charge transport properties of the films. The epitaxial GBCO films mainly consist of single- and double-perovskite regions that are oriented in different directions depending on the deposition temperature. Additionally, cobalt depletion induces the formation of a high density of stacking defects in the films, consisting of supplementary GdO planes along the c-axis of the material. The presence of such defects progressively reduces the electrical conductivity. The films closer to the stoichiometric composition have shown p-type electronic conductivity at high pO2 with values as high as 800 S/cm at 330 °C in 1 atm O2, and with a pO2 power dependence with an exponent as low as 1/25, consistent with the behavior reported for bulk GBCO. These values place GBCO thin films as a very promising material to be applied as cathodes in intermediate temperature solid oxide fuel cells.

The authors acknowledge the financial support of the Spanish Science Ministry through Projects MAT2008-04931NAN and Consolider-Ingenio CSD2008- 00023. M.B. acknowledges the support of her postdoctoral fellowships from the Spanish Ministry of Education (former Spanish Ministry of Science and Education, MEC). S.J.S. and J.A.K. acknowledge support from the EPSRC SOFC platform grant EP/F009720/1 “New Research Directions for Solid Oxide Fuel Cell Science and Engineering”. The authors also acknowledge financial support from the European Union under the Framework 6 program under a contract for an Integrated Infrastructure Initiative (Reference 026019 ESTEEM). H. T. acknowledges the financial support from FWO-Vlaanderen (Project G.0147.06).

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