Effects of spray condition and annealing treatment on oxygen contents of thermally sprayed La_0.5Sr_0.5CoO_3-δ coatings

La_1-xSr_xCoO_3-δ(LSCO) is a promising cathode material for solid oxide fuel cells (SOFCs). The properties of the LSCO cathode are significantly influenced by its oxygen content. In this paper, La_0.5Sr_0.5CoO_3-δ coatings are prepared by both flame spraying and plasma spraying. Annealing treatment of the LSCO coatings is performed at 1 000 °C for 3 hours. Oxygen contents of different samples are investigated by iodine titration. The effects of spray condition and annealing treatment on the oxygen content of the La_0.5Sr_0.5CoO_3-δ are investigated. The results show that oxygen contents in the as-sprayed coatings get significantly lower than that in the starting powder owing to heating to a high temperature of spray particles by high temperature flame. The escaped oxygen of plasma-sprayed La_0.5Sr_0.5CoO_3-δ is more than that of flame-sprayed one. The oxygen content significantly increases after annealing treatment. It is clear that the deficit oxygen can be recovered through annealing treatment. The lattice distortion occurs in the thermally sprayed coatings due to large concentration of oxygen vacancies, which induces tetragonal phase formation. It is also found that recovery of oxygen through annealing treatment leads to a recovery phase transformation from tetragonal phase to perovskite cubic phase.