Electrophoretic co-deposition of Fe₂O₃ and Mn_1,5Co_1,5O₄: processing and oxidation performance of Fe-doped Mn-Co coatings for solid oxide cell interconnects

Fe-doped Mn1,5Co1,5O4 coatings on Crofer22APU were processed by an electrophoretic co-deposition method and the corrosion resistance was tested at 750 °C up to 2000 h. The “in-situ” Fe-doping of the manganese cobalt spinel was achieved by electrophoretic co-deposition of Mn1,5Co1,5O4 and Fe2O3 powders followed by a two-step reactive sintering treatment. The effects on the coating properties of two different Fe-doping levels (5 and 10 wt.% respectively) and two different temperatures of the reducing treatment (900 and 1000 °C) are discussed. Samples with Fe-doped coatings demonstrated a lower parabolic oxidation rate and thinner oxide scale in comparison with both the undoped Mn1,5Co1,5O4 spinel coating and bare Crofer 22 APU. The best corrosion protection was achieved with the combined effect of Fe-doping and a higher temperature of the reducing step at 1000 °C

Area specific resistance of in-situ oxidized Mn-Cu and Mn-Co metal powders as contact layers for the solid oxide cell air side

Stacking of solid oxide cells (SOC) requires that a robust and durable electrical contact is established between the cell and the interconnect. In this work, we present a contact layer solution for the SOC air side based on the concept of reactive oxidative bonding in which metallic Mn-Co and Mn-Cu particles are oxidized in-situ during stack initiation or operation to form robust well-conductive spinel oxides. The long-term (3000 h) stability of the new contact layers is evaluated by measuring the area specific resistance (ASR) during aging in air at 750 °C and 850 °C, and during thermal cycling. Both Mn-Co and Mn-Cu layers are found to be well compatible with a CeCo coated 441 steel interconnect material, and do not significantly contribute to the resistance across the stack element. The resistance is dominated by the coated steel.</p

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 Mn1.5Co1.5O4 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