Chapter 2: Models for the Structures of Germanate Glasses Check Access

Models for the structures of vitreous germania, modifier-free germanate glasses, e.g. SiO₂–GeO₂ glasses, alkali and alkaline earth germanate glasses, and germanate glasses containing a modifier oxide and either an intermediate oxide or a second glassforming oxide are discussed in detail. A major portion of this chapter is devoted to the development of the complex model for the structure of alkali germanate glasses, including the interpretation of studies involving numerous spectral techniques, mathematical models based on the glass composition, and models based on topological arguments. It is shown that the properties of these glasses can only be explained by models which consider both the short and intermediate range network structure. An evaluation of these models and a proposal for the best currently available model for the structure of alkali germanate glasses are presented. Models are also presented for alkaline earth and lead germanate glasses and for germanate glasses containing Al₂O₃, Ga₂O₃, Nb₂O₅ and Ta₂O₅.