Material transport and degradation behavior of SOFC interconnects

The SOFC interconnect materials, both lanthanum chromite based oxides and Fe-Cr ferritic alloys, are discussed from the viewpoint of material transport which causes the degradation in conductivity or chemical stability. The controlling factors, such as effect of oxygen chemical potential gradient, interaction with other cell components, and surrounding gaseous atmospheres are evaluated. The role grain boundary is important in the transport of metal components in oxide materials such as lanthanum chromites, or oxide scales on alloy. The diffusivity of metal components in alloy is much faster, which causes the interdiffusion on nickel and chromium between alloy and anode current collector. The reaction of alloy and sealing materials would be more significant, since the chromium component in alloy easily reacts with alkaline earth components in sealing materials. The slight amount of water vapor in air may greatly enhance the chromium vaporization rate from chromium oxide (Cr₂O₃).