Crystal Structure, Chemical Stabilities and Electrical Conductivity of Fe-Doped Manganese Cobalt Spinel Oxides for SOFC Interconnect Coatings

The application of ceramic coatings has been demonstrated as an effective technique to suppress the oxidation scale growth and chromium volatilization of ferritic stainless steels used for SOFC interconnects. Manganese cobalt spinel oxides are promising materials for this application. In this work, the effects of iron doping in the MnCo 2-x Fe x O 4 (x = 0–0.7) spinel oxide on the crystal structure, reaction with chromia, cation distributions, and electrical conductivity at high temperature were investigated. With increasing the iron content, the lattice parameters increase and the electrical conductivity decreases. During reaction with chromia, iron does not appear in the chromium-rich reaction layer even for the sample with heaviest doping (e.g. MnCo 1.3 Fe 0.7 O 4 ). Neutron diffraction studies suggest that cobalt has a stronger preference for the tetrahedral sites while manganese and iron favor the octahedral sites.