Textured cermets of CeO₂ (or GDC) with Co for solid oxide fuel cells anodes

Cermets composed of submicron size alternating lamellae of CeO₂, or 10% Gadolinia doped Ceria (GDC), and porous-metallic Cobalt have been prepared from eutectic oxide mixtures. A fine eutectic structure was obtained by fast directional solidification of the cobalt oxide-ceria oxide eutectic composite using the Laser Floating Zone (LFZ) technique. The resulting microstructure, with an interphase spacing down to 0.5 μm, was obtained for solidification rates of 750 mm/h. Textured cermets were obtained by subsequent reduction under H₂ containing atmosphere of the eutectic oxide composite. The reduction kinetics was studied in the 550-750 °C temperature range and effective diffusion coefficients were obtained. The reduction process does not correspond to a typical thermally activated process. The cermets are composed of ceria lamellae of about 200 nm thickness alternated with porous-metallic cobalt lamellae of ≤400 nm. The lamellar microstructure of the cermets favours oxygen ion mobility through ceria and its size can be controlled by solidification rate of the eutectic precursor. These materials are proposed as SOFC anodes.