MoO3 incorporation in magnesium aluminosilicate glasses

Molybdate has a very low solubility in silicate and borosilicate glass systems and its excess presence in nuclear waste glass can cause the formation of a readily soluble “yellow phase”. In this study, the incorporation of molybdenum oxide (MoO3) in a magnesium aluminosilicate glass system has been investigated. The prepared glasses show a higher than 90% molybdenum retention rate and up to 5.34 mol% (12.28 wt%) MoO3 can be incorporated into these glasses without causing visible phase separation. The incorporation of MoO3 increases glass density, decreases glass transition and crystallisation temperatures and intensifies Raman bands assigned to vibrations of MoO42− units. When excess molybdate is added liquid-liquid phase separation and crystallisation occurs. The separated phase is spherical, 200-400 nm in diameter and randomly dispersed. Based on powder X-ray diffraction, Raman spectroscopy and transmission electron microscopy, the separated phase is identified as MgMoO4.