Effects of iron on the formation and annihilation of X-ray irradiation induced non-bridging oxygen hole centers in soda-lime silicate glass

With the aim of using the coloration imparted by radiation-induced defects in practical glass products, we have been investigating the effects of the impurity ions in glasses on the formation and annihilation of defects. In the present study, we investigated the formation of non-bridging oxygen hole centers (NBOHCs) induced by X-ray irradiation in soda-lime silicate glasses doped with 0.01–0.59 wt.% of Fe2O3. The 0.02 and 0.07 wt.% Fe2O3-doped glasses contained the greatest amounts of NBOHCs. The NBOHC content decreased in the order 0.01 wt.% doped, undoped, and 0.59 wt.% doped glasses. More NBOHCs were formed in 0.02 and 0.07 wt.% Fe2O3-doped glasses melted in an oxidizing atmosphere than in the same glasses melted in a normal atmosphere. These results can be explained by Fe3+ ions functioning as trapping sites for electrons released from non-bridging oxygen. Annihilation was strongly affected by Fe2+ ions: the relative stability of NBOHCs was highest in the undoped glass and decreased with increasing amount of Fe2+ in the glasses.