Improving LSM Cathode Performance Using (Cu,Mn)3O4 Spinel Coated UNS430 Ferritic Stainless Steel SOFC Interconnects

Maintaining the power output of planar SOFCs cathodes over thousands of hours of operation in air at 700 or even 800 degrees C, requires that the contact resistance of the interconnect remain relatively low over the operation life of the SOFC, and that the generation of volatile Cr species is minimized. This work focuses on assessing the ability of the (Cu,Mn)(3)O-4 spinel oxide coating to limit Cr2O3 film growth and chromia loss from ferritic 430 stainless steel (UNS430). Several orders of magnitude more conductive than the native Cr2O3 oxide film, this material and other spinel coatings have been applied to UNS430 samples using a low cost fabrication method that is amenable to many interconnect geometries. Coated UNS430 samples were tested under simulated half-cell conditions via direct contact to a porous (La0.8Sr0.2)(0.98)MnO3 (LSM) cathode supported on 8%YSZ in flowing dry air at 600 to 800 degrees C. As compared to uncoated UNS430 contacts, spinel-coated interconnects greatly enhance the stability of the cathode when cathodically polarized over a 250+ hour period. WDX analyses show that these films prevent Cr transfer to the LSM-YSZ interface, but are susceptible to long-term loss of Cu.