Diffusion behavior and electrical performance of La2O3 doped Ni-Co films and their application as metallic interconnection of solid oxide fuel cell

The application of spinel coatings has been proposed to overcome the difficulties in ultilizing ferritic stainless steel as interconnection. In this paper, a La2O3-doped (Ni,Co)3O4 coating containing 15 wt% La2O3 was synthesized on a SUS430 stainless steel via codeposition, followed by thermal conversion of the deposited layer in air at 800 celcius for 1000 h. The surface and cross-sectional microstructure of the samples is analyzed by scanning electron microscope, and X-ray diffraction. The results reveal that a tri-layer oxide structure with Co3O4 outer layer, (Ni,Co,Fe)3O4/(Ni,Co)3O4/(Ni,Co)O middle layer and (Mn,Cr)3O4/Cr2O3 inner layer is developed on the Ni-Co-La2O3 coated steel. This work is designed to elucidate the diffusion behavior of elements and the effect mechanism of the La2O3. The addition of La2O3 inhibits the growth of Cr2O3 at the coating/substrate interface. Moreover, a higher electrical conductivity has been achieved for the La2O3-doped coating sample.