Transmission electron microscopy characterization of protective La0.7Sr0.3MnO3−delta coatings prepared by electrostatic spray deposition on ferritic alloy

The effect of La0:7Sr0:3MnO3-delta (LSM) coating on SS446 steel on air oxidation at 800 degrees C was investigated by transmission electron microscopy. Dense and crack free thin LSM films were prepared by electrostatic spray deposition. The microstructural characterization was carried out on coated and uncoated interconnectors. A thin chromia scale at the alloy interface along with two spinel phases were observed after long term oxidation in both cases. Specimens exhibit, in addition, an SiO2 layer at the interface with steel due to the high content of Si in the steel. Significant changes in the thickness, morphology and composition occurred in the reaction layer for the LSM coated steel. These effects are explained on the basis of changes in the diffusive fluxes during exposure to the oxidation treatment. The implications of these effects for the degradation mechanism of LSM-based interconnects are discussed.