Alkali motion in alkali silicate glass

Abstract

Alkali motion in alkali silicate glass was studied by the method of ionic thermocurrent which was developed as a highly sensitive technique for studying relaxation of polarized impurity-vacancy dipoles in ionic crystals. Two current peaks were observed in the temperature range −196–100 °C, and were ascribed to orientational depolarization of pseudodipoles composed of localized alkali–nonbridging oxygen and to thermal relaxation of space charges near the cathode. Heterogeneous distribution of alkalis in alkali silicate glass was verified by large differences in ionic thermocurrent and in the evaluated density of localized alkalis from sample to sample taken from even the same glass film, as well as by the distribution in activation energies for dipolar orientation and space-charge relaxation. It was also concluded that the neutralization process of alkalis in glass was due to tunneling of electrons through the potential barrier in the space-charge–electrode double layer.