Silicate glasses, alkali silicon-oxygen bond

The network-forming structure of silicate glasses, such as alkali or alkaline-earth silicate glasses, is composed of (SiO ) tetrahedra (Kreidl 1983). Because of the tetravalence of silicon, (SiO ) tetrahedra can link together on four corners by means of oxygen ions to form a fiilly three-dimensional network. In alkali or alkaline-earth silicate glasses, the alkali and alkaline-earth ions break Si-O-Si bonds, loosening the (SiO ) tetrahedra network. 

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