SURFACE VERSUS BULK COMPOSITION OF A PHOSPHATE-GLASS

Transmission and conversion electron Mossbauer spectroscopy as well as photoelectron spectroscopy were applied to study alterations of the s urface layer of an iron containing industrial phosphate glass as compa red with its bulk. In the surface layer, after polishing and exposure to ambient atmosphere, Fe2+ is partially oxidized to Fe3+. This oxidat ion, however, does not increase the O/P ratio in this layer, because i t goes along with a strong leaching of network modifiers. This leachin g leads to a net decrease of the O/P ratio because it overcompensates the relative oxygen increase by Fe2+ oxidation and by uptake of water.