Influence of the annealing conditions on the structure of BaCe1−xYxO3−α coatings elaborated by DC magnetron sputtering at room temperature

BaCe1−xYxO3−α coatings were synthesised by magnetron co-sputtering of metallic targets in the presence of reactive argon–oxygen gas mixtures. This material appears to be a valuable candidate for electrolyte in the novel concept of proton conductor fuel cells. In our knowledge, the single study concerning the deposition of this material was performed by radiofrequency sputtering of a perovskite target. In the present study, we focus on its feasibility by reactive magnetron (co-)sputtering. Hence, a first set of experiments was carried out using a single metallic target with the convenient metal content (Ba0.50Ce0.45Y0.05) for the deposition of perovskite structure coatings. Whatever the deposition conditions, the cerium concentration in the coating is very low in comparison with that of the target. In a second set of experiments, the films were synthesised by co-deposition of Ce0.9Y0.1 and Ba metallic targets to increase their Ce content. The composition of the coatings was then controlled by the discharge parameters. Whatever their composition in the range (Ce + Y)/Ba between 0.3 and 1.1, as-deposited coatings are amorphous and those with higher Ba content present a poor chemical stability against carbonation or hydration. As-deposited coatings with the convenient Ba content, i.e. Ba/(Ce + Y) ∼ 1, are also amorphous. They crystallise after annealing around 873 K for 2 h under air in a mixture of BaCO3 and CeO2 in spite of the targeted Y-substituted BaCeO3 perovskite structure. Nevertheless, the crystallisation in the convenient perovskite structure was obtained after annealing under vacuum to prevent the carbonation of the coating.