Effect of Na2O and CaO on the solubility and crystallization of Mo in borosilicate glasses

Abstract The effect of Na2O and CaO on the solubility and crystallization of Mo in the conventional borosilicate glasses belonging to SiO2-B2O3-Na2O-CaO system was investigated. The results show that the solubility of Mo in the glasses reaches up to 2.98 mol%. The substitutions of cationic oxides ([Na2O]+[CaO]) for SiO2 and CaO for Na2O in the glass composition improve the solubility of Mo. The solubility and crystallization of Mo are related to the depolymerized regions of the glass structure. Generally, the improved solubility of Mo can be ascribed to the high depolymerization degree of glass structure and the loose distribution of ions in the depolymerized regions. Product consistency test (PCT) results show the crystalline CaMoO4 has insignificant influence on the normalized elemental leaching rate of Mo. The normalized leaching rates of the obtained samples are ~10−3 g·m−2·d−1 after 28 days, which are comparable to widely used borosilicate waste glasses.