The types of sol-gel are distinguished by the precursor used. The colloidal route utilises fine powder to form multicomponent systems, such as aluminosilicates. The polymeric route employs smaller scale precursors such as alkoxides, which give greater flexibility in the end product than the colloidal route, making it the most commonly used sol-gel route.
Sol-gel can produce uniform crystalline particle size powders, which allows greater morphological control leading to greater homogeneity and purity. Sol-gel derived materials can be fully densified at temperatures 70% lower than conventionally produced powders. This is due to the production of nano-sized powders leading to an inherently high surface area. Sol-gel can be used to fabricate dense structures for use in the SOFC, or be tailored to the substrate material and be used as a surface sealant.
Sol-gel coatings can be modified with additives to provide functional properties such as adhesion, abrasion and corrosion resistance. Application of the sol-gel solution to the substrate is either through spinning, dipping or spraying. Thin films of