Measurement of viscosity of multi-component glasses in the wide range for fiber drawing

The viscosity-temperature behavior in the wide range 10^-2∼10¹²Pa·s were presented for various glass systems: oxide, fluoride, halide, and chalcogenide. There is no single technique that can be utilized to measure the viscosity of glass over the entire range, spaning roughly 14 orders of magnitude. The viscosity was measured by a penetration viscometry method at low-temperature viscosity region (10⁷∼10¹² Pa·s) and by a rotational viscometry method at high-temperature viscosity region (10^-2∼10¹ Pa·s). It was found the viscosity can be expressed by the Cohen-Grest equation over a wide temperature. The working point, T_w(10³ Pa·s), the softening point, T_s(10^6.65 Pa·s) and the working range-temperature interval between the T_w and the T_s were determined using the measured viscosity data and the viscosity-temperature equation. We discussed the technical term of fiber drawing from the viewpoint of viscosity-temperature behavior and thermal stability of glass crystalized as a function of heat treatment time, t_D at the drawing temperature. The results indicate that silica and lead silicate glasses are prefered for fiber drawing.