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

Abstract

U-, Th- and Ce-doped pyrochlores were synthesized by solid state reaction: (Ca 0.62Gd 0.97U 0.23)(Zr 0.84Ti 1.34)O 6.9, (Ca 0.47Gd 0.95Th 0.40)(Zr 1.29Ti 0.89)O 7.05, (Ca 0.44GdTh 0.42)Zr 2.13O 7.05, Ca 0.91Th 0.84Zr 2.25O 7.09 and Ca 1.04Ce 0.97Ti 1.99O 6.96. Their response to the radiation damage from the recoils of the alpha-decay events has been simulated by 1 MeV Kr 2+ 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.