Electrical Properties, Cation Distributions, and Thermal Expansion of Manganese Cobalt Chromite Spinel Oxides

As the oxidation and chromium volatilization of chromia-forming alloy interconnects can cause Solid oxide fuel cells (SOFC) cathode poisoning and cell degradation, spinel coatings like Mn1.5Co1.5O4 have been applied as a barrier to oxygen and chromium diffusion. To evaluate their long-term stability, the properties of the reaction layer between the Mn1.5Co1.5O4 coating and Cr2O3 scale formed on the alloy surface need to be characterized. Therefore, compositions of Mn1.5−0.5xCo1.5−0.5xCrxO4 (x = 0–2) were prepared to investigate their electrical properties, cation distributions, and thermal expansion behavior at high temperature. With increasing Cr content in manganese cobalt spinel oxides, the cubic crystal structure is stabilized and the electrical conductivity and coefficient of thermal expansion both decrease. The cation distributions determined from neutron diffraction show that Cr and Mn have stronger preference for octahedral sites in the spinel structure as compared with Co.