Preparation and characterization of borosilicate glass-ceramics containing zirconolite and titanite crystalline phases

CaCO3, ZrSiO4, and TiO2 (abbreviated as CZST) in the stoichiometric mole ratio (2:1:3) were added to borosilicate system. Borosilicate glass-ceramics containing zirconolite and titanite crystalline phases were prepared by controlled crystallization of the parent glass. The effects of CZST addition (10, 20, 30, and 40 wt. %) on crystalline phases, microstructure, and chemical durability of the glass-ceramics were mainly investigated. The results show that the samples possess the amorphous structure when the concentration of CZST is lower than 30 wt. %. For the glass-ceramics with 30 wt.% CZST (GC-30) heated at 740 degrees C for 2 h, only the zirconolite-2M phase was observed. For the sample with 40 wt. % CZST (GC-40) heated at 810 degrees C for 2 h, the major crystalline phases are CaZrTi2O7 and CaTiSiO5. In addition, the grains of the CaZrTi2O7 and CaTiSiO5 show a dendritic and columnar shape, respectively. The static leaching test shows that the normalized mass loss (NL,) for B, Si, and Na of the sample GC-30 remains almost unchanged (similar to 10(-3) g/m(2)) after 14 days. Compared to the borosilicate glass, the GC-30 possesses particularly the lower values of the NL, for B and Na. These results indicate that the borosilicate glass-ceramics containing zirconolite and/or titanite crystalline phases have the potential as host materials for actinide-rich high level radioactive wastes. (C) 2013 Elsevier B.V. All rights reserved.