Copper-Magnesium-Manganese Spinel Coatings For Solid Oxide Fuel Cell Interconnects

The properties of Cu-Mn-O spinels containing Mg were studied for use as protective coatings on UNS430 stainless steel interconnects in solid oxide fuel cells. Cu-Mn-Mg-O spinel coatings were formed by oxidizing electrodeposited copper, manganese, and magnesium hydroxide films in air at 800 degrees C. A base layer of copper aided uniform manganese deposition and uniform spine! formation. The Mg-Mn-O pseudobinary phase diagram based on XRD results shows a wide range of spinet non-stoichiometry. The CuMn2O4 spinel coating has higher conductivity (similar to 100 S/cm at 800 degrees C) but exhibited buckling defects. Addition of magnesium to the Cu-Mn-O spinel coatings significantly reduced the buckling damage. Although the measured electrical conductivity of MgMn2O4 is 1-2 S/cm at 800 degrees C, Cu0.7Mg0.3Mn2O4 has a conductivity of similar to 60 S/cm at 800 degrees C. Cu-Mn-Mg-O spinel coatings also protect stainless steel by significantly reducing chromium oxide scale formation and diffusion of chromium into the coatings with the advantage of relatively high conductivity. (C) 2013 The Electrochemical Society. All rights reserved.