Radiation Effects of Y_2−xCe_xTi₂O_7+y Pyrochlores Induced by Low- and Medium-energy Ion Beams

Pyrochlores are potential immobilization matrices of high-level radioactive waste, and it is important to study the irradiation effect of pyrochlore immobilization matrices. Y_2−xCe_xTi₂O_7+y (x = 0, 0.2, 0.4, 0.6) pyrochlores were irradiated by 400 keV Ne²⁺ and 6.5 MeV Xe²⁶⁺ at room temperature at an average dose of about 0.16 dpa. Under 400 keV Ne²⁺ irradiation, the samples undergo lattice disorder, phase separation and partial amorphization in sequence with increasing Ce content. Under 6.5 MeV Xe²⁶⁺ irradiation, the damage in samples is more significant than that of the samples irradiated by Ne²⁺, but no phase separation is observed in all the samples. This difference in the damage process may be related to the rate of defect accumulation. The proportion of nuclear energy loss of 6.5 MeV Xe ions in Y_2−xCe_xTi₂O_7+y is 29.88%, which is larger than that of 400 keV Ne ions (17.15%), leading to a faster defect accumulation and more stable defect clusters in the samples irradiated by Xe ions, and therefore amorphization occurs directly from disordered pyrochlores. This result may contribute to the selection of ion beam species and energies with specific irradiation modification objectives.