Spectrum of relaxation times in GeO2 glass

Abstract

Index-of-refraction versus time isotherms have been established for germania glass. Using the crossover technique with air-quenched samples and applying the two relaxation time model previously reported for borosilicate glass, it was found that the width of the spectrum of relaxation times for germania glass was temperature dependent. Upon analyzing this in terms of a distribution of activation energies, the results showed that, similarly to B2O3, activation energies smaller than the activation energy present in the Arrhenius region appear at low temperatures. Extensive viscosity measurements by the fiber elongation method were made from 1011 to 6 X 1014 poises. From this data a lower and more precise value of the activation energy (E? = 72.3 kcal/mol) was obtained in the annealing range.