The effects of temperature and Ce-dopant concentration on the synthesis of zirconolite glass-ceramic.

Zirconolite based glass-ceramic has been deemed as a promising waste form for high-level waste (HLW). In this study, the zirconolite (nominally CaZrTi 2 O 7) glass-ceramic based on a SiO 2 -B 2 O 3 -Na 2 O-CaO-ZrO 2 -TiO 2 -Al 2 O 3 system was sought to be synthesized by two-step thermal treatment. The temperature effects such as nucleation temperature and cooling rate were studied. The influence of the Ce-dopant concentration on crystallization behavior was also investigated. For characterization, powder X-ray diffraction (XRD), thermogravimetry-differential scanning calorimeter (TG-DSC) and scanning electron microscopy (SEM) were applied. Our results illustrate that homogeneous zirconolite with the particle size of 1.8 μm can be the target phase when the glass matrix underwent a rapid cooling process and the nucleation temperature was controlled at around 860 °C. Besides, the results also indicate that the distribution of the zirconolite along with its lattice parameters change regularly as the increase of CeO 2 concentration. A larger crystal size of zirconolite phase and some trace amounts of precipitated phases are observed when the CeO 2 concentration exceed 3 wt%. This work emphasizes the synthesis of zirconolite glass-ceramic in a SiO 2 -B 2 O 3 -Na 2 O-CaO-ZrO 2 -TiO 2 -Al 2 O 3 system, which is expected to provide basic technical data for underground disposal of HLW. [ABSTRACT FROM AUTHOR]