A low-Cr metallic interconnect for intermediate-temperature solid oxide fuel cells

A new low thermal expansion, low-Cr, Fe–Co–Ni base alloy was developed and evaluated as interconnect for intermediate-temperature solid oxide fuel cells (SOFCs). This alloy demonstrated good oxidation resistance, low oxide scale area specific resistance and a reasonable match in coefficient of thermal expansion with adjacent cell components. A double-layer oxide structure with an highly conductive, Cr-free (Fe,Co,Ni)3O4 spinel outer layer and a thin protective Cr2O3 inner layer was formed on the alloy surface upon thermal exposure in air at 800 °C. The existence of the Cr-free (Fe,Co,Ni)3O4 outer layer effectively reduced the Cr evaporation and in transpiration testing resulted in a six-fold decrease in Cr evaporation as compared to a state-of-the-art ferritic interconnect alloy. The new low-Cr alloy also exhibited good scale spallation resistance and adequate compatibility with the cathode material La0.8Sr0.2MnO3 (LSM).