Protective coatings for SOFC interconnects – thermal expansion and electrical conductivity of Fe or Cu doped MnCo2O4 spinel

The lifetime and performance of solid oxide fuel cell stacks is today greatly limited by oxidation of the stainless steel interconnect. In order to reduce the oxidation rate and prevent chromium evaporation, (Mn,Co)3O4 spinel has been identified as a promising coating material. We want to investigate if the properties that are important for interconnect coatings can be further improved by partly substituting Co with Fe or Cu. MnCo2-xMxO4 (M = Cu, Fe, x = 0; 0,1; 0,3; 0,5) powders were synthesized by spray pyrolysis and all found to be single phase, cubic spinels. The thermal expansion coefficient was found to decrease with increasing amount of Fe, while the behavior of Cu-doped compositions was more complex. The electrical conductivity of these compositions between 500 and 800°C will also be presented. Based on the results we discuss how these improved coatings will function in a fuel cell.