Self-propagating High-temperature Synthesis of Sm and Zr Co-doped Gd2Ti2O7 Pyrochlore Ceramics as Nuclear Waste Forms

We reported a rapid synthesis of Sm 3+ /Zr 4+ co-doped Gd 2 Ti 2 O 7 pyrochlore simulated nuclear wastes solidification by self-propagation plus quick pressing technique. With increment excess contents of Sm 2 O 3 and ZrO 2 from 0 to 10wt%, the phase composition of the products is a mixed phase of pyrochlore structure and defective fluorite structure by X-ray diffraction (XRD) analysis and Raman spectrum. In addition, the SEM results demonstrate the fracture surface and microstructure of Gd 2 Ti 2 O 7 -based pyrochlore. The densified pyrochlore waste form exhibits high bulk density of 5.56 g·cm −3 and vickers hardness of 11.20±0.2 GPa. The leaching tests show that the elemental leaching rates of Gd, Sm, and Cu after 42 days are 1.92×10 −4 , 1.51×10 −4 , and 3.90×10 −3 g·m −2 ·d −1 , respectively.