Structural aspects of barium borosilicate glasses containing thorium and uranium oxides

Barium borosilicate glasses incorporated with 15.86 wt% ThO2 and containing different amounts of uranium oxide were prepared by conventional melt quench method. Based on 29Si and 11B magic angle spinning nuclear magnetic resonance (MAS NMR) studies, it has been confirmed that uranium oxide incorporation is associated with distortion of borosilicate network as revealed by the increase in the relative concentration of Q2 structural units of silicon as well as the increase in the quadrupolar coupling constant (Cq) of BO3 structural units. The increased number of non-bridging oxygen atoms brought about by the increase in Q2 structural units of silicon facilitates the incorporation of both uranium and thorium ions in the sites created by non-bridging oxygen atoms (network modifying positions) in the glass. Uranium oxide incorporation above 7.5 wt% resulted in the phase separation of ThO2 as revealed by the X-ray diffraction studies. The present study focuses on the structural changes with the borosilicate network of barium borosilicate glasses brought about by the introduction of thorium and uranium ions.