Ion beam implantation and cross-sectional TEM studies of lanthanide titanate pyrochlore single crystals

We have performed ion implantations in bulk samples of single crystal lanthanide titanate pyrochlores A2Ti2O7 (A = Sm, Eu, Gd, Dy and Er) using 1.0 MeV Kr+ at room temperature at an ion fluence of 5 × 1014 ions/cm2. Er2Ti2O7 was also implanted by 1 MeV Kr+ at an ion fluence of 1.74 × 1014 ions/cm2. Ion implantation-induced microstructural evolution has been examined using cross-sectional TEM. For Er2Ti2O7 irradiated by 1 MeV Kr+ at a dose of 1.74 × 1014 ions/cm2, a highly damaged layer consisting of nano-sized disordered fluorite domains was observed; while, a complete amorphous layer starting from surface was created by 1 MeV Kr+ implantation at a fluence of 5 × 1014 ions/cm2. The critical amorphization doses of different titanate pyrochlore single crystals implanted with 1 MeV Kr+ were determined by comparing the experimental damage profiles with those simulated using SRIM-2000. The critical amorphization doses generally increase as the A-site cation changes from Sm3+ to Er3+, suggesting that the radiation resistance of titanate pyrochlores increases with the decreasing ionic radius of A-site cations.