Structural studies of ThO2 containing barium borosilicate glasses

Abstract Barium borosilicate glasses containing as much as 18.6 wt% ThO 2 have been prepared by a conventional melt–quench method and characterized by 29 Si and 11 B magic angle spinning nuclear magnetic resonance (MAS NMR), Infrared (IR) absorption and differential thermal analysis (DTA) techniques for their structural features. Based on 29 Si and 11 B MAS NMR and IR investigations, it has been established that the borosilicate network is not affected by such a large ThO 2 incorporation. Whereas Si exists as Q 3 and Q 2 structural units in the ratio of ∼0.7, boron exists in both trigonal (BO 3 ) and tetrahedral (BO 4 ) configurations and their relative concentrations are not affected by ThO 2 incorporation in these glasses. The higher extent of ThO 2 incorporation in barium borosilicate glasses compared to borosilicate glasses has been attributed to the increased number of non-bridging oxygen atoms present in the barium borosilicate glasses. Based on DTA measurements it has been shown that there is neither any change in the glass transition temperature nor the occurrence of any crystallization up to 1000 °C, for ThO 2 incorporation up to 18.6 wt% in these glasses. For higher concentrations of ThO 2 , there is phase separation during glass formation and fine crystallites of ThO 2 are formed as revealed by XRD. These findings are of significance for the nuclear waste management related to thorium fuel cycle.