Vapor-Phase Deposition for Dense CeO2 Film Growth on Porous Substrates

Pure and Sm-doped CeO 2 thin films were deposited on porous substrates by vapor-phase deposition, which is similar to the well-known electrochemical vapor deposition (EVD). By supplying metal chlorides (MCl 3 , M; Ce and Sm) vapor and oxygen to a disk-shaped porous substrate from opposite directions, a dense oxide film was grown on the chloride side of the substrate with high homogeneity. The films deposited are suitable for the electrolytes in the ceria-based intermediate temperature solid oxide fuel cells (SOFCs). The growth kinetics of these films was also discussed along with an observed growth rate and theoretical analysis based on oxygen flux and oxygen potential gradient over the film and the substrate. It was found that the film growth was governed by rates of each competitive process: diffusion of oxygen molecules through substrate pores, oxygen reduction (O 2 2 O 2- ) at the film/substrate interface, and transport of electrochemical species (O 2- and e - ) through the growing dense film.