Water-dispersed silicates and water-soluble phosphates, and their use in sol-gel synthesis of silicate- and phosphate-based materials

Silicon and phosphorous are important elements in materials science. There are less proper raw materials for synthesis of their compounds by aqueous solution- based sol-gel methods, because the conventional raw materials have low stability in aqueous conditions and/or high reactivity with other elements such as metal ions. In this chapter, preparation, chemistry, property, and stability of glycol-modified silanes (GMSs) and glycol-conjugated phosphate esters are summarized. The former is dispersed in an aqueous solution as silicon clusters, and the latter is dissolved in water. In addition, their applications for synthesis of silicates and phosphates by aqueous solution-based sol-gel methods are also documented using examples. The materials obtained showed high performance and phase purity caused by homogeneity of constituents at the atomic level. It is also clearly showed that introduction of such unconventional raw materials enables us to develop new compounds and new synthetic routes for synthesizing high-performance materials.