Magnetron-sputtered Mn/Co(40:60) coating on ferritic stainless steel SUS430 for solid oxide fuel cell interconnect applications

With recent progress in lowering the operating temperature, chromia-forming ferritic stainless steels are considered as promising interconnect materials for solid oxide fuel cells (SOFCs). To block the chromium evaporation and chromium poisoning, coatings with Mn/Co (40:60) was tested as the optimized recipe to maintain Mn_1.5Co_1.5O₄ composition after long term operation due to Mn diffusion from substrate. In order to study the coating thickness effect, Mn/Co (40:60) coatings were fabricated in thickness of approximately 800 nm, 1500 nm, 3000 nm on ferritic stainless steels SUS430 using magnetron sputtering. Oxidation behavior of sputtered samples was investigated after oxidized at 800 °C in air for 2 h, 250 h, 500 h, 1000 h, respectively. SEM, EDS, XRD and FIB are used to analyze the surface morphology, chemical composition and structures of the coatings. Area specific resistance measurement indicated the sputtered samples in thickness of 800 nm, 1500 nm, 3000 nm at 800 °C for various hours in air are in range of 15-36 mΩ cm², 12-25 mΩ cm², 10-23 mΩ cm² respectively. Eventually the optimized thickness of Mn/Co (40:60) coatings was suggested.