Investigation of thermally oxidised Mn–Co thin films for application in SOFC metallic interconnects

Thin metallic Mn–Co films (0.3 μm thickness) were produced by RF-magnetron co-sputtering on SiO2/Si and on ZMG232L steel substrates. The deposition was followed by a heat treatment in order to convert the metallic coatings to (Mn,Co)3O4 spinel oxides. All steel samples were analyzed after 1 h heat treatment in order to confirm the presence of the spinel structure on top of the steel, as well as to investigate and characterise the evolution and growth of oxides, namely (Mn,Cr)3O4 and Cr2O3, at the internal steel/coating interface. From the structural and morphological characterization, the presence of a well-adherent approximately 0.5 μm thick Mn1.5Co1.5O4 coating was confirmed. After this preparatory annealing, selected samples were heat-treated in simulated cathodic or anodic atmospheres at 800 °C for 500 h in order to investigate the properties of the coatings after long time annealing. For the samples annealed in cathodic-like atmospheres, Cr was present on the surface of the coating, whereas for the samples annealed in anodic-like atmospheres, MnO was the main phase observed on the surface. Measurements of the area specific resistance performed on the steel coated with Mn50Co50 showed a resistivity of around 59 mΩ cm after 601 h annealing in ambient air.