Gadolinium solubility in peralkaline borosilicate glasses

This paper discusses the results of a study, using 25 peralkaline (Na/Al>1) borosilicate glasses, to understand the effect of glass composition on the Gd solubility. In the glasses with the ratio of excess Na2O, i.e., moles of Na2O minus the moles of Al2O3, to B2O3 less than 0.5, phase separation occurs above the Gd solubility. In the glasses, with excess Na/B ratio greater than 0.5, sodium gadolinium silicate crystallizes above the Gd solubility. For the samples in which phase separation occurs, the Gd solubility is determined by the concentration of excess Na. Increasing excess Na increases the Gd solubility. For the samples in which crystallization occurs, the Gd solubility is determined by the concentration of each glass former. Increasing B and Si increases the Gd solubility, but increasing Al decreases it. The solution mechanism of Gd in peralkaline borosilicate glasses is discussed.