Color Centers in Alkali Silicate and Borate Glasses

Abstract

The color centers induced by x-ray irradiation in the alkali silicate and borate glasses and the mixed alkali glasses are studied. By preparing samples of various compositions in the reducing and in the oxidizing condition, and by optical and thermal bleaching, it is concluded that the visible band is due to electrons trapped by oxygen vacancies neighboring alkali ions and that the ultraviolet band is due to positive holes trapped by alkali ion vacancies neighboring oxygen ions.