Electrophoretic deposition and low-temperature densification of Cu_1.35Mn_1.65O₄ spinel for an interconnect protective coating in solid oxide fuel cells

As a protective coating of the interconnects in solid oxide fuel cells, spinel-structured Cu_1.35Mn_1.65O₄ powder was coated onto 460FC stainless steel by using the electrophoretic deposition method. A suitable amount of iodine was added to ethanol to charge the spinel powder with a high zeta potential value. Stainless steel substrates were immersed in a slurry, and a DC voltage in the range of 20–60 V was applied for 30–120 s. Because a low-temperature densification of the coated film is crucial for minimizing Cr out-diffusion from the stainless steel substrate, the coated spinel was decomposed into Cu and MnO by applying a heat treatment at 800 °C in a 5% H₂/95% N₂ atmosphere. Then, it was oxidized at 700 °C in air, leading to appropriate densification. The area-specific resistance of the films was 15–29 mΩ cm² after 1000 h at 700 °C in air.