Effects of aluminum impurity on the structural relaxation in silica glass

To elucidate effects of Al impurity on the glass-forming process in silica glass, the structural relaxation in Al-containing silica glass, with alkali ions of only trace levels, was investigated by observing the fictive tempe rature. The fictive temperature was determined by infrared (IR) absorption analysis. Al, even at concentrations lower than 10 wtppm, increases the rel axation time and the activation energy of the alpha-relaxation. It also sup presses the sub-relaxational process due to OH ions. These results indicate d that Al should have other effects on structural relaxation than alkali-al uminate complex formation. as has been thought to be the cause for an incre ase in the alpha-relaxation time and thus the viscosity of silica glass. Fu rthermore, the structural relaxation does not merely depend on the number o f non-bridging oxygen atoms in the glass network. (C) 2000 Elsevier Science B.V. All rights reserved.