Liquidus temperature of phosphate crystalline phases in borosilicate waste glasses

Abstract The formation of phosphate crystals in high‐level waste (HLW) glass may hinder the steady operation of the melter and deteriorate the chemical durability of the final waste form. Exploring the liquidus temperature ( T L ) of phosphate crystals is important to estimate the solubility limit of phosphorus in borosilicate waste glass across complex compositions. In this study, a borosilicate waste glass matrix was statistically designed using the space filling method. A linear extrapolation method was used to determine the T L for each crystalline phase. Isothermal heat‐treatment temperature and crystal fraction (CF) data were applied as dependent variables and independent variables respectively for linear fitting to extrapolate T L . These new datapoints on the T L of phosphate crystals were combined with T L data reported elsewhere into one dataset to fit empirical models. Linear and nonlinear models were developed using the least squares regression to predict the T L of phosphate‐containing crystals as a function of melt compositions. The addition of CaO and P 2 O 5 strongly increased, while Li 2 O and MgO decreased the T L of the phosphate‐containing phases in the glass.