Viscosity of GeO2-doped silica glasses

The viscosity of GeO₂-doped silica glasses is experimentally evaluated and found to be expressed as a function of the monoexponential form η₀ exp(-AΔe), where η₀ is the viscosity of pure silica glass, A is a positive constant, and Δe is an equivalent relative-index difference that is introduced for a silica glass with nonuniform dopant distribution in its cross section. The constant A for GeO₂-doped silica glasses is found to be about 0.5, which is much smaller than that for fluorine-doped silica glasses and has almost no temperature dependence between 1400°C and 2200°C