ION-EXCHANGE PROCESSES IN SILICATE-GLASSES - THE ROLE OF OXYGEN

Concentration gradients in soda-lime-silica glass subjected to an ion exchange in molten KNO3 at a temperature below the strain point of the glass were explored by Auger electron spectroscopy. Measurement showe d an excess of oxygen in the modified layer of glass and similar shape s of potassium and oxygen concentration profiles over most of the modi fied region. Replacement of smaller sodium ions by larger potassium io ns appears to be accompanied by oxygen diffusion from molten salt into glass. On the basis of these results, a microscopic model for ion-exc hange processes in silicate glasses, including mixed alkali effect, is proposed. (C) 1998 Elsevier Science B.V. All rights reserved.