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

Abstract

We reported a rapid synthesis of Sm³⁺/Zr⁴⁺ co-doped Gd₂Ti₂O₇ pyrochlore simulated nuclear wastes solidification by self-propagation plus quick pressing technique. With increment excess contents of Sm₂O₃ and ZrO₂ 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 Gd₂Ti₂O₇-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.

Keywords

SHS / pyrochlore / immobilization of nuclear wastes / excess

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