Cerium doping-mediated structural conversion of ZIT glass-ceramic waste form for efficient nuclides immobilization

Zinc Titanate (ZIT) glass-ceramic matrix is a promising candidate for immobilizing radioactive Eu element based on the reactions between Eu and raw material of Zn 2 TiO 4 /CaHPO 4 . However, the generated Eu 2 Ti 2 O 7 ceramic with unstable fluorite defect structure hampers the mechanical properties and chemical durability of ZIT-Eu (ZIT glass-ceramic waste form immobilized with Eu 2 O 3 ). This study addresses the issue by developing the Ce-doping ZIT-Eu waste forms using a solid-phase sintering method at high temperature, realizing the conversion from unstable defective fluorite to stable pyrochlore. As evidenced by the experimental measurements, the density, hardness, water absorption and chemical stability are significantly improved after Ce doping, with the 6 wt% Ce exhibiting the best aqueous durability, retaining a leach value of only 0.11 × 10 −9 g·m −2 ·d −1 at 90 ℃ after 28 days. Furthermore, the density functional theory calculation reveals the potential mechanism that Ce doping decreases the adsorption capability for H 2 O and increases the lattice energy for Eu ion diffusion. In conclusion, this simple doping strategy promotes the application of ZIT glass-ceramic matrix in the field of radioactive waste treatment.