Fused silica dielectric properties

Table 8. Dielectric Properties of Synthetic Fused Silica ...

Properties Colorless crystals or white powder odorless and tasteless. D 2.2-2.6 thermal conductivity about half that of glass, mp 1710C, bp 2230C, high dielectric constant, high heat and shock resistance. Insoluble in water and acids except hydrogen fluoride soluble in molten alkai when finely divided and amorphous. Combines chemically with most metallic oxides melts to a glass with lowest known coefficient of expansion (fused silica). Noncombustible. 

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Temperature. The dielectric constant of glass increases with rising temperature in proportion to the polarizability of the medium. When stability of the dielectric properties is required, glasses with rigid structures, e.g., fused silica and high-siUca glasses, are used. 

Table 10.2 Some examples of positive and negative effective Hamaker constants. The magnitude of the van der Waals attraction increases with the difference in dielectric properties between the medium and the particles. Fused quartz is glass containing silica in amorphous form. The Hamaker constant for air is here taken to be 0...

Figure 16 Dielectric properties of fused silica (Corning 7940). (After Inglesias and Westphall, MIT, 1967).

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