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Polycrystalline pyrochlore Lu 2 Ti 2 O 7 was irradiated with 200 keV He + ions at room temperature to fluences ranging from 2.0×10 15 to 2.0×10 17 He + /cm 2. Irradiation-induced microstructural evolution was examined by grazing incidence X-ray diffraction and crosssectional transmission electron microscopy. A micro-swelling (lattice expansion) induced by cation ion disordering was observed, which an obvious swelling was achieved at a fluence of 2.0×10 16 He + /cm 2 , and saturated at a fluence of 1.0×10 17 He + /cm 2 with cation ions fully disordered. Furthermore, during the irradiation process, the pristine pyrochlore phase was found to form by a fluence of 5.0×10 16 He + /cm 2 , corresponding to an average ballistic damage dose of ~0.25 displacements per atom (dpa) for the near surface examined region. No amorphization was observed even to the highest fluence of 2.0×10 17 He + /cm 2. The experimental observations are further discussed in the context of antisite formation in the pyrochlore Lu 2 Ti 2 O 7 .

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In this research, Zr-doped Gd 2 Ti 2 O 7 pyrochlores, with the composition of Gd 2 (Ti 1x Zr x) 2 O 7 , were firstly synthesized by self-propagating high-temperature synthesis plus quick pressing (SHS/QP) using CuO as the oxidant and Ti as the reductant. To improve the radiation resistance of titanate-pyrochlore, up to 35 at% Zr was incorporated to substitute the Ti site of Gd 2 Ti 2 O 7 pyrochlore (Gd 2 (Ti 0.75 Zr 0.35) 2 O 7). XRD and SEM microstructural characterizations showed the formation of a composite ceramic with the major pyrochlore phase and the minor Cu phase. The generated temperature of samples decreased from 1702 to 1011 ℃ with increasing Zr content. The effects of sintering temperature and pressure time on phase composition and microstructure were systematically studied. Besides, the influence of thermal transmission on the whole combustion process was also explored. The pyrochlore-based waste form possessed high bulk density of 6.25 g/cm 3 and Vickers hardness of 10.81 GPa. The MCC-1 leaching test showed the normalized elemental leaching rates (42 d) of Cu, Gd, and Zr are 1.27×10 2 , 1.33×10 3 , and 8.44×10 7 g•m 2 •d 1 , respectively.