Materials Science Forum, Vol.461-464, 1099-1106, 2004
Interfacial interactions between some La-based perovskite thick films and ferritic steel substrate with regard to the operating conditions of SOFC
An overview is presented on the oxidation kinetics, electrical properties and microstructure investigations of the oxide products formed on Fe-25 wt.-%Cr steel uncoated and coated with electrical conducting films of (La,Ca)CrO3 or (La,Sr)CoO3 in air and H-2/H2O gas mixture at 1023-1173 K for up to 480 hrs with regard to their application as the SOFC metallic interconnect. The application of the Fe-25Cr steel in SOFC operating at 1073 K requires its surface modification to improve the electrical conductivity of chromia scale forming on the uncoated steel surface. The thick films of (La,Ca)CrO3 and (La,Sr)CoO3 with the thickness range of 20-100 mum, coated on the Fe-25Cr steel by screen-printing method helped solve this problem. TEM-SAD, SEM-EDS and impedance spectroscopy investigations have shown significant influence of the multilayer products formation at the substrate steel/coating films interfacial zone on the electrical properties of the metallic interconnect.
Keywords:SOFC interconnect;chromia scales;(La,Ca)CrO3 or (La,Sr)CoO3 thick film;microstructure;electrical properties;kinetics