Manganese cobalt spinel oxides are promising materials for protective coatings for solid oxide fuel cell (SOFC) interconnects. To achieve high density such coatings are often sintered in a two-step procedure, involving heat treatment first in reducing and then in oxidizing atmospheres. Sintering the coating inside the SOFC stack during heating would reduce production costs, but may 2 result in a lower coating density. The importance of coating density is here assessed by characterization of the oxidation kinetics and Cr evaporation of Crofer 22 APU with MnCo 1.7 Fe 0.3 O 4 spinel coatings of different density. The coating density is shown to have minor influence on the longterm oxidation behavior in air at 800 °C, evaluated over 5000 h. Sintering the spinel coating in air at 900 °C, equivalent to an in-situ heat treatment, leads to an 88 % reduction of the Cr evaporation rate of Crofer 22 APU in air-3% H 2 O at 800 °C. The air sintered spinel coating is initially highly porous, however, densifies with time in interaction with the alloy. A two-step reduction and re-oxidation heat treatment results in a denser coating, which reduces Cr evaporation by 97 %.

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Manganese cobalt spinel oxides are promising coating materials for corrosion protection of metallic interconnects in solid oxide fuel cell stacks. This work investigates how Fe and Cu doping affect the crystal structure, thermal expansion and electrical conductivity of the MnCo2-xMxO4 (M=Cu, Fe; x = 0.1, 0.3, 0.5) spinel oxides. Single phase cubic spinels were successfully prepared by spray pyrolysis. The electrical conductivity between room temperature and 1000 °C increased with addition of Cu and decreased with addition of Fe. The thermal expansion coefficient (TEC) between 50 and 800 °C decreased from 14.4 to 11.0×10-6 K-1 going from MnCo2O4 to MnCo1.5Fe0.5O4. The TEC of the Cu substituted materials did not follow any obvious trend with composition and was likely influenced by precipitation of CuO during heating. Based on their physical properties, the Fe doped materials are the most attractive for application as SOFC interconnect coatings.