Iron doped manganese cobaltite spinel coatings produced by electrophoretic co-deposition on interconnects for solid oxide cells: Microstructural and electrical characterization

We report a systematic microstructural and electrical characterization of iron doped Mn–Co spinel coatings processed by electrophoretic co-deposition of Mn_1.5Co_1.5O₄ and Fe₂O₃ powders on Crofer 22 APU and AISI 441 steel substrates. Iron addition to Mn–Co spinel coating leads to a reduction of the area specific resistance on both substrates, after 3200 h at 750 °C. The Fe doped Mn–Co coating both leads to a thinner oxide scale and reduces the sub scale oxidation for the Crofer 22 APU substrate. Fe doped Mn–Co on AISI 441 shows both a thicker oxide scale and low area specific resistance values, likely due to a doping effect of the oxide scale by minor alloying elements. The different mechanisms by which iron doping of Mn–Co spinels can influence elemental interdiffusion at the steel-oxide scale-coating interfaces and relative contributions to the overall area specific resistance are evaluated by means of advanced electron microscopy. The promising results are further confirmed in a cell test, where the Fe doped MnCo coated interconnect does not induce any degradation of the oxygen electrode, proving its efficiency.