Glasses Terms Links

Quartz crystals are composed of silica, Si02. When the silica is pure, as here, it is colorless. The internal structure of quartz is highly complex, but can be pictured in terms of tetrahedral Si04 units, linked through shared oxygen atoms. When quartz crystals melt and solidify again, they may form an amorphous material known as a glass, in which the tetrahedral units form a more random jumble. 

Solid phosphates show a huge variety of crystal structures, and it is not practical to classify them in terms of structural types as is done with simple oxides, halides, etc. However, some general classes of metal phosphate structures will be considered three-dimensional frameworks of linked phosphate tetrahedra and tetrahedrally or octahedrally coordinated cations, layered phosphates, and phosphate glasses. In all of these materials the size and topology of pores within the structure are of importance, as these determine the ability of ions and molecules to move within the structure, giving rise to useful ion exchange, ionic condnction, or catalytic properties. Ion exchange can also be nsed to modify the properties of the host network, for example, the nonlinear optical behavior of potassium titanyl phosphate (KTP) derivatives. 

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