Ion beam irradiation of U-, Th- and Ce-doped pyrochlores

U-, Th- and Ce-doped pyrochlores were synthesized by solid state reaction: (Ca0.62Gd0.97U0.23)(Zr0.84Ti1.34)O6.9, (Ca0.47Gd0.95Th0.40)(Zr1.29Ti0.89)O7.05, (Ca0.44GdTh0.42)Zr2.13O7.05, Ca0.91Th0.84Zr2.25O7.09 and Ca1.04Ce0.97Ti1.99O6.96. Their response to the radiation damage from the recoils of the alpha-decay events has been simulated by 1 MeV Kr2+ ion irradiation and studied by in situ transmission electron microscopy (TEM). An ion beam-induced pyrochlore-to-fluorite structural transition occurred for all compositions, and independent kinetics were observed for cation and anion disordering processes. Similar to the stoichiometric titanate and zirconate pyrochlores, the Ti-rich compositions are susceptible to ion beam-induced amorphization; while, the Zr-rich compositions are more radiation “resistant”. A close relation between the critical amorphization temperature of the U-, Th- and Ce-doped pyrochlores and the average cation ionic radius ratio of the A- and B-sites was observed.