PNNL

Abstract

Lanthanide-containing glasses, commonly used for optical and laser applications, are also important in the vitrification of actinide-bearing radioactive wastes. In order to study the effect of glass composition on the solubility of gadolinium, 25 peralkaline (Na/Al >1) borosilicate glasses were studied. Above Gd solubility, liquid-liquid phase separation was found in the glasses with Na/B less than 0.5; and in the glasses with Na/B more than 0.5, crystallization was found. For the samples from which liquid-liquid phase separation was observed, Gd solubility was mostly decided by the concentration of excess Na (e.g. Na-Al). Increasing excess Na will increase Gd solubility. For the samples from which crystallization was observed, Gd solubility was decided by the concentration of B, Si, and Al. Increasing B and Si will increase Gd solubility, but increasing Al will decrease Gd solubility. The solution mechanism of Gd in peralkaline borosilicate glasses is also discussed.