Gadolinium solubility in peraluminous borosilicate glasses

This paper discusses the results of a study with 18 peraluminous (Na/Al<1) borosilicate glasses to understand the effect of glass composition on Gd solubility. Above Gd solubility limit, phase separation occurs in some of the glasses; in the others, sodium gadolinium silicate crystallizes. For the samples in which phase separation occurs, Gd solubility is determined by the [AlO1.5]–[NaO0.5]–0.2[BO1.5] values in the melt. Increasing [AlO1.5]–[NaO0.5]–0.2[BO1.5] increases Gd solubility. For the samples in which sodium gadolinium silicate crystallizes, Gd solubility is determined by the concentration of Na. Increasing Na decreases Gd solubility. When Al concentration in the baseline glass is high, a minimum amount of Gd is needed to form a clear glass. Otherwise, mullite crystallizes. The minimum concentration of Gd is determined by the [AlO1.5]–[NaO0.5]–[BO1.5] value in the melt. The higher this value, the more Gd is needed to form a clear glass. In general, the solution behavior of Gd in peraluminous borosilicate melts is similar to that in peralkaline borosilicate melts.