A novel sol–gel coating method for fabricating dense layers on porous surfaces particularly for metal-supported SOFC electrolyte

This paper presents a study on a solution coating process for depositing layers on porous surfaces, i.e., metal-supported SOFC electrolyte. PVP and nanoparticles are used to achieve the study objectives. PVP, which possesses a type of coiled long chain structure, can increase the solution viscosity and relieve stress. However, PVP can react with nitrate ions, consequently generating excessive ignition, which causes an inhomogeneous microstructure and forms many defects. The application of nanoparticles can control the stress and reduce cracks. Subsequently, to densify and repair the cracks, an additional solution coating process is applied. YSZ is selected as a candidate, and OCV and SEM measurements are conducted to confirm the YSZ density. The YSZ solution is multi-coated to the GDC layer, and a fully dense layer can be deposited on the coated GDC surface. The proposed coating process can fabricate a dense electrolyte under oxidation environments at a relatively low temperature using a wet-chemical process. Furthermore, in terms of spin coating and heat treatment, it can be continuously and automatically performed. Therefore, the multi-coating process developed in this research can be readily commercialized.