Coating of SOFC Metallic Interconnects and Their Oxygen Diffusivity

La_0.8Sr_0.2Co_0.2Fe_0.8O₃ (LSCF) coating on Fe-Cr alloy was examined for use as interconnects in SOFC. Thermal cyclic oxidation was conducted on the LSCF coated Fe-Cr alloy to evaluate the interface evolution at LSCF/oxide scale/Fe-Cr alloy. The thickness of oxide scales increased at the LSCF coating/Fe-Cr alloy interfaces with increasing the number of thermal cycles. SIMS depth profiles were obtained after thermal cycling for the LSCF/alloy interfaces region: the oxide scale consisted of (Fe)-Mn-Cr spinel, Cr₂O₃, and SiO₂. Elemental distribution of oxide scales is very similar to the non-coated Fe-Cr alloy. A relatively high diffusivity of oxygen (oxide ions) was observed within the LSCF coating. However, the diffusion of oxygen was blocked by the oxide scales, especially at the Cr₂O₃ region. The oxide scale growth rates were effectively reduced by the LSCF coating on the Fe-Cr alloy. The effects of the LSCF coating on the oxide scale growth are discussed.