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

Abstract

Thin metallic Mn–Co films (0.3 μm thickness) were produced by RF-magnetron co-sputtering on SiO 2/Si and on ZMG232L steel substrates. The deposition was followed by a heat treatment in order to convert the metallic coatings to (Mn,Co) 3O 4 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) 3O 4 and Cr 2O 3, at the internal steel/coating interface. From the structural and morphological characterization, the presence of a well-adherent approximately 0.5 μm thick Mn 1.5Co 1.5O 4 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 Mn 50Co 50 showed a resistivity of around 59 mΩ cm after 601 h annealing in ambient air.