15: Doped Vitreous Silica

Dopants have a small, but very useful, effect on the density, refractive index, and thermal expansion coefficient of vitreous silica. The addition of a dopant may either increase or decrease the values of each of these properties. All dopants reduce the viscosity and glass transformation temperature. Some dopants have a very large effect on the reactivity of the glass with hydrogen and water vapor, as well as the effect of radiation on optical spectra. The three dopants studied (F, Cl, and TiO2) also significantly alter the effect of T_f on the properties of these glasses.