Multi-component glasses

The conventional multi-component glasses contain alkali and alkaline earth ions and frequently also aluminum oxide, boric oxide and other oxide components, depending upon the particular application. They can be remelted and processed at much lower temperatures than quartz. Network-formers also act as a flux, their flux activity increasing with their polarizability. Thus, K2O is a better flux than Li20. 

The constraints model sketched above has a natural extension to it. In network forming multi-component glasses such as 432 (Ge-As-Se) chalcogenide glasses, locally there will be the regions of the structure where the average coordination, (mi) is lower than mo. Such regions are easily defonnable and are described as floppy, under constrained or... 

Evidently in such multi-component glasses of simple halides, significant lowering of the eutectic temperatures and of course, the confusion principle, together assist formation of glasses. 

Most of the reported studies of the effect of water concentration on the properties of glasses deal with vitreous silica. Since the effects of water are so small, very slight changes in composition of multi-component glasses would overshadow the effect of water. There are questions regarding the validity of many of these studies even for vitreous silica, since the various types of commercial silica contain different amounts of impurities, especially chlorine, aluminum, and alkali. 

Holand W, Schweiger M., Cramer von Clausbruch S., and Rheinberger V, "Complex Nucleation and Crystal Growth Mechanisms in Applied Multi-Component Glass-Ceramics," Glastech. Ber. Glass Sci. Technol, 73 [Cl[ 12—19 (2000a). 

There are several methods based on a structural approach. They consider glass or melt properties connected with structural groups or elements. The structure-properties relations in multi-component glasses, however, are quite complex and often unknown. This leads to free interpretation of properties changes, and higher uncertainty in their prediction. Known based-on-structure methods work well in case of glasses with a few components, and within a narrower compositional range. 

The multi-component glasses of the following systems will be taken as exanples and discussed ... 

The refractive index of a compound oxide or a multi-component glass may be roughly estimated by using the Lorenz-Lorentz formula (Clausius-Mosotti s formula in terms of the dielectric constant and polarizability) which gives the relation between the refractive index and polarizability of materials described as equation (31-1). 

The right hand side ofthe above equation is called specific refraction which has a value specific to each material. When the material is made up of several types of molecules of which interactions are small, we may recognize that the additive property of specific refraction ofthe molecules is nearly established (Miyauchi, 1984). Therefore, we can roughly estimate the refractive index of the materials such as compound oxides or multi-component glasses from the density and specific refraction of component as... 

Notwithstanding the huge improvement in experimental methodologies, like X-ray Absorption Fine Structure, Neutron Diffraction, Nuclear Magnetic Resonance, Infrared and Raman spectroscopy, the elucidation of the glass structure still remain a difficult task [4]. In fact, quite often, difficulties in data interpretation of multi-component glasses and apparent contradictory structural evidences from different techniques have to be faced. 

Eden, M. (2011) The split network analysis for exploring composition-structure correlations in multi-component glasses 1. Rationalizing bioactivity-composition trends of bioglasses. /. Non-Cryst. Solids, 357, 1595-1602. 

M. Tokuyama. Self-diffusion in multi-component glass-forming systems. Physica A, 388 (2009), 3083-3092. 

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