The effect of composition on spinel crystals equilibrium in low-silica high-level waste glasses

The liquidus temperature (T_L) and the equilibrium mass fraction of spinel were measured in the regions of low-silica (less than 42 mass% SiO₂) high-level waste borosilicate glasses within the spinel primary phase field as functions of glass composition. The components that varied, one at a time, were Al₂O₃, B₂O₃, Cr₂O₃, Fe₂O₃, Li₂O, MnO, Na₂O, NiO, SiO₂, and ZrO₂. In the low-silica region, Cr₂O₃ increased the T_L substantially less, and Li₂O and Na₂O decreased the T_L significantly less than in the region with 42-56 mass% SiO₂. The temperature at which the equilibrium mass fraction of spinel was 1 mass% was 25-64 °C below the T_L.