Metallic interconnects for SOFC: Characterization of their corrosion resistance in hydrogen/water atmosphere and at the operating temperatures of differently coated metallic alloys

Abstract

Chromia forming alloys are one of the best candidates for the interconnecting materials in solid oxide fuels cells (SOFC). Recent research has enabled to decrease the operating temperature of the SOFC from 1000 °C to 800 °C. However, low electronic conductivity and high volatility of the chromia scale need to be solved to improve performance of interconnects. In the field of high temperature oxidation of metals, it is well known that the addition of reactive elements into alloys or in thin film coatings, improve the oxidation resistance of alloys at high temperature. The elements of the beginning of the lanthanide group and yttrium are the most efficient. The goal of this study is to make rare-earth oxides coatings by MOCVD (Metal Organic Chemical Vapour Deposition) on Crofer 22 APU alloy in order to form perovskite oxides which possess good conductivity at high temperatures. The coatings were analysed after 100 h ageing at 800 °C by SEM, TEM, EDX and XRD analyses. ASR (Area Specific Resistance) was measured in air for the same times and temperature, using a four point technique with Pt paste for electrical contacts between surfaces. In conclusion reactive elements have beneficial effects on the oxidation behaviour (decrease of the oxidation rate) as well as on the stability of the electrical conductivity as proved by the value of ASR parameter.