Abstract
Darkening and fading characteristics of germanate glasses in the systems Na2S-GeO2 and Na2S-B2O3-GeO2 were investigated. These glasses darkened by irradiation of U.V. light and the darkening faded by heat treatment. The most effective wavelength for the darkening is found to be 460mμ. The degree of darking increases with increasing U.V. irradiation time and reaches a saturated value at about 60 minutes. However, it decreases with increasing Na2S and B2O3 contents in the glasses.
The activation energy for fading process of all glasses used was obtained to be 9∼10kcal/mol from the plot of fading rate as a function of reciprocal temperature. It is suggested that the darkening and fading mechanism of the glass can be interpreted on the basis of an electronic conduction model.
