Structure continued silicate glasses

The structure of vitreous silica consists of a continuous, random network of corner-sharing Si04 tetrahedra. Extending this model to alkali silicate glasses requires that the alkali cations be regarded as network modifiers, as shown in Figure 11 The addition of each alkali oxide unit results in the replacement of... 

In the metals, the same type of interatomic force acts between atom of different metals that acts between atoms of a single element. We have already stated that for this reason liquid solutions of many metals with each other exist in wide ranges of composition. There, are many other cases in which two substances ordinarily solid at room temperature are soluble in each other when liquefied. Thus, a great variety of molten ionic crystals are soluble in each other. And among the silicates and other substances held by valence bonds, the liquid phase permits a wide range of compositions. This is familiar from the glasses, which can have a continuous variability of composition and which can then supercool to essentially solid form, still with quite arbitrary compositions, and yet perfectly homogeneous structure. 

Crystalline phosphates and phosphate glasses continue to receive attention as potential hosts for the immobilization and disposal of radionuclides, particularly actinides and waste streams with a high phosphorous content. The principal crystalline phases considered are apatite, silicates with the apatite-structure, and monazite. As has been discussed by Lutze and Ewing (1988a), there are a number of factors that have to be considered in selecting a nuclear waste form. The most important are ... 

In crystalline silicates the isotropic linewidths are usually sufficiently narrow so that it is possible to resolve crystallographically distinct sites [117]. In contrast, such a resolution cannot be achieved in glasses as a result of the inhomogeneous broadening of the isotropic line owing to the continuous distribution of NMR parameters which arises from a continuous distribution of structural parameters [118, 119]. 

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