Effects of boron on structure of lanthanum and sodium aluminoborosilicate glasses studied by X-ray diffraction, transmission electron microscopy and infrared spectrometry

Study of glasses with a high content of rare earth elements has a particular interest due to their use in nuclear waste storage. New glass matrices are required to immobilize even higher concentrations of high-level waste in comparison to borosilicate glasses already used. We study the effect of aluminum/boron substitution on the structure of peraluminous lanthanum-rich sodium aluminoborosilicate glasses of 55SiO(2)-(25-x)Al2O3-xB(2)O(3)-15Na(2)O-5La(2)O(3) composition, where lanthanum simulate all the lanthanides as well as the minor actinides typical for the high-level waste. We have here chosen a chemical composition of a model glass that can accept the presence of minor actinides among the fission products generated by the new reactors of the fourth generation. Transmission Electron Microscopy, Differential Scanning Calorimetry, X-ray diffraction and Infrared spectroscopy showed the existence of phase separation at high boron oxide concentrations, and finely characterized the structure of the major vitreous network.