Effect of Nd2O3 dosages and melting temperatures on pyrochlore borosilicate glass-ceramics immobilization

Abstract

In this study, borosilicate glass-ceramic waste forms containing pyrochlore crystalline phase (PBGC) were prepared by one-step heat-treated method. The effect of Nd2O3 dosages and melting temperatures on the crystalline phases and microstructure of PBGC were studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Product Consistency Test (PCT) was used to investigate the aqueous durability of PBGC. The 14 wt% Nd2O3 doping in PBGC contributes to the formation of pyrochlore (Ca,Na)(Nb,Ti)2Nd0.67O6F. The optimal supercooling region of the glass-ceramic is from the melting temperature of 1325 °C to the initial cooling temperature of 1000 °C. The prepared glass-ceramic has a stable pyrochlore crystalline structure. In addition, the normalized leaching rates of major elements in PBGC are comparable to those of standard reference glass for immobilization of high-level wastes (HLWs). The results of this study provide useful guidance on the immobilization of certain HLWs in the industry using glass-ceramic materials.