Self-propagating plus quick pressing synthesis and characterizations of Gd2-xNdxTi1.3Zr0.7O7 (0 ≤ x ≤ 1.4) pyrochlores

Synroc is recognized as an ideal matrice for the immobilization of high-level radioactive waste (HLW). In this study, the Synroc mineral of pyrochlore was employed as host phase for the immobilization of Nd2O3, which was selected as surrogate of trivalent actinide nuclides. Gd2-xNdxTi1.3Zr0.7O7/Cu composites were rapidly synthesized by self-propagating high-temperature synthesis plus quick pressing (SHS/QP) using CuO as the oxidant and Ti as the reductant. The result shows that the Nd2O3 doped reactions could be ignited as x ≤ 1.4 and Gd2-xNdxTi1.3Zr0.7O7 pyrochlores were successfully prepared with Cu as the secondary phase. The synthesized pyrochlore-based waste form exhibits density of 4.93 g/cm3 and Vickers hardness of 14.90 GPa, as well as promising aqueous durability. The LRGd and LRNd value of the x = 1.4 sample are as low as 3.28 × 10−5 and 2.27 × 10−5 g m−2·d−1 after 42 days leaching.