Effect of MoO₃, Nd ₂O ₃, and RuO ₂ on the crystallization of soda–lime aluminoborosilicate glasses

The effect of adding Nd₂O₃, MoO₃, and RuO₂ separately or simultaneously on the crystallization of a soda–lime aluminoborosilicate glass during cooling from the melt or glass heating was studied by DTA, XRD (at room and high temperature), SEM, Raman, and optical absorption. Nd₂O₃ addition strongly reduces liquid–liquid phase separation and crystallization of calcium and sodium molybdates (CaMoO₄ (powellite) and Na₂MoO₄) in Mo-rich compositions as long as Nd³⁺ ions remain solubilized in the glassy network. This suggests that (MoO₄)²⁻ entities and Nd³⁺ ions are close to each other in the glass structure (Nd³⁺ ions would prevent the clustering of molybdate entities). The effect of MoO₃ addition in Nd-rich compositions is more complex since an increase of the solubility of Nd₂O₃ is observed, whereas the nucleation rate of an Nd-rich silicate apatite (Ca₂Nd₈(SiO₄)₆O₂) in the bulk of the glass increases as soon as molybdates crystallized. The addition of RuO₂ has a nucleating effect on apatite crystallization in the bulk but not on molybdates crystallization.