Heavy ion irradiation effects of brannerite-type ceramics

Brannerite, UTi2O6, occurs in polyphase Ti-based, crystalline ceramics that are under development for plutonium immobilization. In order to investigate radiation effects caused by a-decay events of Pu, a 1 MeV Kr+ irradiation on UTi2O6, ThTi2O6, CeTi2O6 and a more complex material, composed of Ca-containing brannerite and pyrochlore, was performed over a temperature range of 25-1020 K. The ion irradiation-induced crystalline-to-amorphous transformation was observed in all brannerite samples. The critical amorphization temperatures of the different brannerite compositions are: 970 K, UTi2O6; 990 K, ThTi2O6; 1020 K, CeTi2O6. The systematic increase in radiation resistance from Ce-, Th- to U-brannerite is related to the difference of mean atomic mass of A-site cation in the structure. As compared with the pyrochlore structure-type, brannerite phases are more susceptible to ion irradiation-induced amorphization. The effects of structure and chemical compositions on radiation resistance of brannerite-type and pyrochlore-type ceramics are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.