Effects of Ni-Doping in CuMn₂O₄ Spinel Coatings for Interconnects in Solid Oxide Fuel Cells

Chromium (Cr) poisoning from metallic interconnects is a significant issue that impairs the performance of solid oxide fuel cells (SOFCs). Employing doped spinel coatings as a protective layer on interconnects has proven to be a successful mitigation strategy for Cr poisoning. This study examines three different nickel (Ni) doping levels in CuMn₂O₄ spinel to determine the most effective doping content. The compositions explored were CuNi_0.2Mn_1.8O₄, CuNi_0.4Mn_1.6O₄, and CuNi_0.6Mn_1.4O₄. Results indicate that Ni doping enhances the phase stability and electrical conductivity and reduces Cr diffusion in the CuMn₂O₄ spinel. Notably, CuNi_0.2Mn_1.8O₄ demonstrated best overall performance, exhibiting the highest electrical conductivity of 94–103 S/cm in the 700–800°C range, forming the densest coating layer, and exhibiting the strongest diffusion barrier to Cr migration. Thus, CuNi_0.2Mn_1.8O₄ is identified as the optimally Ni-doped Cu-Mn spinel coating.