Review—(Mn,Co) ₃ O ₄ -Based Spinels for SOFC Interconnect Coating Application

With the reduction of solid oxide fuel cell (SOFC) operating temperature to the range of 600 °C–800 °C, Cr-containing ferritic alloys have become the preferred interconnect material, which unfortunately are susceptible to continuous scale growth and Cr volatility at the SOFC operating temperatures. The (Mn,Co) ₃ O ₄ spinel system is widely regarded as the most effective coating for SOFC interconnect protection, due to its high thermal and electrical conductivity, adequate coefficient of thermal expansion, and excellent Cr blocking capability. This article reviews the physical and chemical properties of the (Mn,Co) ₃ O ₄ -based spinels; different types of coating precursors and deposition techniques; and the effects of spinel composition, quality and thickness on the coating performance. It is concluded that the spinel coating composition, quality, and thickness are more critical than the coating process in affecting the overall coating performance.