Dense spinel MnCo₂O₄ film coating by aerosol deposition on ferritic steel alloy for protection of chromic evaporation and low-conductivity scale formation

Conducting ceramic layers with a spinel structure of MnCo₂O₄ and a thickness of ~3 μm were deposited on ferritic stainless steel (SS) by aerosol deposition (AD), for use as an oxidation-resistant coating layer on the metallic interconnects of a solid oxide fuel cell (SOFC). The microstructural changes in the interface between the MnCo₂O₄ and SS were analyzed, as were the subsequent electrical conductivity changes at an SOFC operating temperature of 800 °C in air. The coated spinel layers were dense without pores or cracks, and maintained good adhesion even after oxidation at 800 °C for 1,000 h in air atmosphere. Close observation of the interface between the coated spinel oxide and SS substrate indicated the presence of ~1-μm thick, Cr-rich scale formation; however no MnCrCoO₄ or MnCr₂O₄ spinel phase was detected. The area specific resistance (ASR) of the MnCo₂O₄-coated alloy after heat treatment at 800 °C for 1,000 h was 13.4 mΩ cm².