Behaviour of refractive index of quartz glasses in glass-transition temperature range

Properties responsible for the processes of forming refractive index and aging, were studied for quartz glasses of KU1 and KS4B grades. Viscosity, temperature coefficients of equilibrium lines of refractive indices and annealing numbers had been measured. Quartz glasses belong to gradientless glasses. When changing cooling rates in the limits of four orders, the measurements of refractive indices don't exceed (2-3)×10-6. In cooling rates more than 500 grad/h the refractive index close to minimum is formed in glass of KU1 grade, but close to maximum in KS4B. Quartz glasses are unstable both in temperature range of glass-transition and in the field of room temperatures. These glasses belong to aging materials.