Post-mortem evaluation of oxidized atmospheric plasma sprayed Mn-Co-Fe oxide spinel coatings on SOFC interconnectors

Interconnects employed in solid oxide fuel cells require electrically conductive protective coatings such as those based on manganese cobalt oxide spinels in order to prevent evaporation of volatile Cr(VI)-compounds and to minimize high temperature corrosion. MnCo2-xFexO4 based (where x = 0.1 and 0.3) oxide spinel protective coatings were manufactured by the atmospheric plasma spraying process on Crofer 22 APU substrates. The coated substrates were oxidized at 700 °C in air for 1000 h and post-mortem analyses were conducted to study the performance of the thermal sprayed coatings. During the high temperature oxidation, a four-point on-line measurement technique was used for area specific resistance studies. The MnCo1.7Fe0.3O4 coating was tested together with the La0.85Sr0.15Mn1.1O3-spacer. The atmospheric plasma sprayed MnCo2-xFexO4 showed excellent Cr-barrier properties and decreased oxidation of the substrate. In addition, resistance as low as 9.20 m{\Omega} cm2 values was obtained after the 1000 h oxidation cycle. The MnCo1.9Fe0.1O4 coating manufactured by the atmospheric plasma spraying process is a promising candidate for SOFC interconnect applications.