The synthesis of glasses via the so-called "sol-gel" process has been widely developed during the past two decades. These synthesis usually involve wet chemistry reactions are are based on the inorganic polymerization of molecular precursors. Precursors are mixed at the molecular level and multicomponent glasses may form at temperatures well below the melting point. Sol-gel chemistry allows the powderless processing of glasses and ceramics. Thin films or fibres can be produced directly from the solution by such techniques as dip-coating, spin-coating or spin-drawing. Moreover, the mild chemical conditions associated with he process allow the synthesis of hybrid glasses in which organic molecules are intimately mixed with the silica network. These new materials fill the gap between plastic organic polymers and brittle silica glasses.
