Structure of Oxide Glasses

Calas, G. Petiau, J. (1983) Structure of oxide glasses Spectroscopic studies of local order and crystallochemistry. Geochemical implications. Bull. Mineral., 106,33-55. 

The concept of random structure of oxidic glasses was first suggested by Zacharia-sen (1932) and later on confirmed by -ray studies by Warren et al. in 1933— 1938. Zachariasen has formulated crystallochemical postulates with which the given oxide has to comply to be glass forming, that is, it forms glass readily on cooling down. 

The present concepts on the structure of oxidic glasses differ from the random network hypothesis particularly in that existence of regularly arranged or hetero-... 

Zachariasen, W.H. (1932) The atomic arrangement in glass, J. Am. Chem. Soc. 54, 3841. Describes a model for the structure of oxide glasses that has become a standard for these materials. 

S. K. Lee, Effect of Pressure on Structure of Oxide Glasses at High Pressure Insights from Solid-State NMR of Quadrupolar Nulides , Solid State Nucl. Magn. Resort., 2010, 38, 45. 

To avoid possible complications resulting from changes in lifetime as a function of composition or concentration, the doping level was held at 10 mole per cent. This was done in an attempt to keep the structure of the glass matrix the same in all samples and thus avoid spurious effects. Sometimes the doping would be all active oxides in others an inert oxide such as Y203 would be added to make the level up to 10 mole per cent. 

Measurements of absorption spectra of oxides, glasses and hydrates of transition metal ions have enabled crystal field stabilization energies (CFSE s) in tetrahedral and octahedral coordinations to be estimated in oxide structures (see table 2.5). The difference between the octahedral and tetrahedral CFSE is called the octahedral site preference energy (OSPE), and values are summarized in table 6.3. The OSPE s may be regarded as a measure of the affinity of a transition metal ion for an octahedral coordination site in an oxide structure such as spinel. Trivalent cations with high OSPE s are predicted to occupy octahedral sites in spinels and to form normal spinels. Thus, Cr3, Mn3, V3+... 

This is, even to a greater extent, true of oxide glasses with the coordination number Z > 6. It is obvious that with another increase in pressure to P 1 Mbar (the stability region of an a-PbC>2 structure type), the coordination number in glassy silica should slightly rise [98] and approach eight at P 2-3 Mbar (the stability region of a pyrite-like structure of crystalline silica). This state of the... 

Amorphous materials have no long-range structural order, so there is no continuous lattice in which atoms can vibrate in concert in order for phonons to propagate. As a result, phonon mean free paths are restricted to distances corresponding to interatomic spacing, and the (effective) thermal conductivity of (oxide) glasses remains low and increases only with photon conduction (Figure 8.2). 

Kawazoe, H., H. Hosono, and T. Kanazawa (1978a). Electronic structure and properties of oxide glasses (I) ir-electron distribution of alkali borate glass networks. J. Noncryst. Solids 29, 159-71. 

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