Effect of spray parameters on the electrical conductivity of plasma-sprayed La1−xSrxMnO3 coating for the cathode of SOFCs

Lanthanum strontium manganate (LSM) perovskite oxide has been widely employed as cathode materials for solid oxide fuel cells (SOFCs). Plasma spraying is a promising cost-effective process to deposit La1−xSrxMnO3 cathode. In this study, the La0.8Sr0.2MnO3 layer was deposited at different plasma powers and spray distances to examine the effect of spray parameters on the electrical conductivity of the LSM deposits. The electrical conductivity of the deposits along the lamellar direction was measured by a four-probe dc technique. The microstructure of the deposit was characterized by electron microscopy and X-ray diffraction analysis. The results showed that the electrical conductivity of plasma-sprayed LSM coating was lower than that of bulk sintered material of the same compositions. It was recognized that the change of the electrical conductivity of plasma-sprayed LSM coatings with spray parameters coincided with the tendency of the lamellar interface bonding ratio. The lamellar structure features with the limited interface bonding limited the electrical conductivity. Moreover, it was also found that the minor metastable phase in the as-sprayed coating reduced the electrical conductivity. The annealing treatment at a high temperature led to the elimination of the metastable phase and improved the electrical conductivity. The dependency of electrical conductivity of the deposit on the microstructure is discussed.