Effect of CeO 2 Content on Viscosity Behavior and Structure Evolution in CaO‐SiO 2 ‐TiO 2 ‐ZrO 2 ‐CeO 2 Glasses

ABSTRACT Zirconolite‐containing waste form is considered one of the most effective materials for the stable immobilization of actinide nuclides. Meanwhile, melt viscosity plays a crucial factor that significantly influences the construction of the zirconolite phase. In this study, the viscosity of CaO‐SiO 2 ‐TiO 2 ‐ZrO 2 ‐CeO 2 glasses with varying CeO 2 contents was first measured using the rotating cylinder method. The microstructure of synthesized glassy samples was then characterized using Raman spectroscopy, 29 Si solid‐state nuclear magnetic resonance (NMR), and X‐ray photoelectron spectroscopy (XPS), respectively. The results indicate that the viscosity decreases with increasing CeO 2 content from 1 wt.% to 5 wt.%, and the activation energy for viscous flow decreases from 186.07 to 156.16 kJ·mol −1 . As a multivalent element, cerium dissociates into trivalent (Ce 3+ ) and tetravalent (Ce 4+ ) ions in the molten glass. These ions subsequently influence the viscosity via different mechanisms. Ce 3+ acts as a network modifier within the silicate network, while Ce 4+ tends to incorporate into the silicate tetrahedral units and disrupts their local structure. The coupled effect of Ce 3+ and Ce 4+ ions reduces the overall degree of polymerization of the glass, thereby leading to a decrease in viscosity. The results of this work provide valuable data for the design of glass composition in the waste form.