Modification of Surface Oxide Layer of Fe‐Cr‐Al Alloy with Coating Materials for SOFC Applications

We investigated the treatment of Fe-Cr-Al alloy for application in solid oxide fuel cells (SOFCs). The electrical resistance of the Al2O3-based surface oxide layer on the alloy decreased and was stable when La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), La0.8Sr0.2MnO3 (LSM), LaNi0.6Fe0.4O3 (LNF), or Pr0.8Sr0.2MnO3 (PrSM) were first coated on the alloy and heat treated at 700 °C in air. The activation energy, calculated from the resistance, also suggested that the surface oxide became more conductive with treatment. The surface oxide layer after treatment had a microstructure of columns growing outward in the same direction, containing small amounts of elements such as Sr, Ni, Fe, La, Mn, and Pr. The microstructure consists of polycrystalline γ-Al2O3 and small amounts of Al compounds with these elements. In the case of the LNF coating, the formation of NiAl2O4 was observed. The enhanced electrical conductivity may have resulted from the arrangement of the columnar structure, along with the electronic conduction path generated by the reaction of γ-Al2O3 with these elements.