Perovskite and Spinel Functional Coatings for SOFC Metallic Interconnects

The oxidation kinetics, electrical properties, microstructure and chromium vaporization effects of the oxide products formed on Fe-25 wt.-%Cr steel uncoated and coated with films of (La,Sr)CrO3, (La,Sr)CoO3, (La,Sr)(Co,Fe)O3, Mn1.5Cr1.5O4 and MnCo2O4 in air and the Ar-H2-H2O gas mixture at 1023−1173 K for up to 840 h with regard to their application as SOFC metallic interconnect were investigated. To improve poor electrical conductivity of chromia scales and to suppress chromium vaporization from this scale grown on uncoated steel during oxidation, the perovskite and spinel thick films composed of paste prepared via co-precipitation-calcination and ultrasonic spray pyrolysis methods were applied. Perovskite and spinel coatings decreased the volatilization rate of chromia species in comparison with the value of this parameter corresponding to oxide scales built mainly of chromia formed on uncoated steel. Microstructure investigations by the SEM-EDS method and electrical resistance measurements revealed the significant influence of the formation of multilayer reaction products at the steel/coating interface on the electrical properties of the composite materials used for the construction of the SOFC metallic interconnect.