Effects of water content on aluminosilicate glasses and the relation to strong/fragile liquid theory

The effect of variations in water content on the transformation range properties of 25Na 2O25Al 2O 350SiO 2, 10Na 2O10CaO20Al 2o 360SiO 2, 20CaO20Al 2O 360SiO 2, and 20Y 2O 320Al 2O 360SiO 2 glasses are presented. Samples of these glasses were prepared with a range of water of hydroxyl contents by melting under various partial pressures of water. With an increase in water content of each glass, a decrease in both the glass transformation temperature, T g, and the transformation range viscosity are observed. The magnitude of these effects of water depends strongly on composition and is correlated with the activation energy for viscous flow. The data from this study are combined with the known effects of water on the properties of phosphate, borate, heavy metal fluoride, and other silicate glasses to show that the flow properties of ‘strong’ liquids are affected much more dramatically than those of ‘fragile’ liquids. These data are used to determine a quantitative empirical relationship between the magnitude of the effect of water on flow properties and the fragility of the glass-forming liquid.