A comparison between radiation damage accumulation in oxides with pyrochlore and fluorite structures

Ion irradiation damage experiments were performed on single crystals of the pyrochlore compound Er2Ti2O7 and the fluorite compound Er2Zr2O7. Results indicate that the pyrochlore compound is far more susceptible to defect accumulation and amorphization than the fluorite compound. In particular, Er2Ti2O7 irradiated with 350 keV Xe++ ions succumbs to an amorphization transformation by a fluence of 1 × 1015 Xe/cm2, while Er2Zr2O7 remains crystalline with no change in crystal structure to at least 5 × 1016 Xe/cm2. Atomistic computer simulations were used to explain this difference in radiation damage behavior between compounds with similar structures. Simulations of defect formation energies reveal that point defects induced by irradiation, such as cation antisite and anion Frenkel pairs, are far more stable in the fluorite compound than in the pyrochlore compound.