Chromium transport by solid state diffusion on solid oxide fuel cell cathode

Abstract

Iron–chromium ferritic stainless steel is widely used in solid oxide fuel cell (SOFC) components. At 650–800 °C, stainless steels form a protective chromia oxide scale. This low conductivity catalytic compound can degrade SOFC cathode performance. The migration of Cr species onto the cathode occurs through vapor transport and/or solid state diffusion, and electrochemical reactions may affect the migration. It is important to understand the relative Cr transport and reaction rates to evaluate the most viable commercially available cathode material. This study characterizes the migration of Cr species through solid state diffusion and vapor deposition. Chromia blocks and chromia-forming stainless steel interconnects were held in contact with LSM (Lanthanum Strontium Manganese Oxide), LSCF (Lanthanum Strontium Cobalt Ferrite) and LNF (Lanthanum Nickel Ferrite) perovskite pellets in Cr-saturated air at 700 °C for 300 h. XRD (X-ray Diffraction), SEM (Scanning Electron Microscope), EDS (Energy Dispersive X-ray Spectroscopy) and Ion Milling by FIB (Focused Ion Beam) were used to detect Cr on and within the perovskite pellets. Cr transport and reaction on LSCF is the most severe, followed by LSM. Cr transport is observed on LNF, but without noticeable reaction.