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

Abstract

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) 3O 4 spinel outer layer and a thin protective Cr 2O 3 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) 3O 4 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 La 0.8Sr 0.2MnO 3 (LSM).