In situ observation of radiation induced amorphization of crystals with apatite structure

摘要

Temperature dependence of amorphization doses for 1.5 MeV Kr ion-irradiated Ca(sub 10)(PO(sub 4))(sub 6)F(sub 2) and Ca(sub 2)La(sub 8)(SiO(sub 4))(sub 6)O(sub 2) were studied with in situ transmission electron microscopy. At low temperatures, Ca(sub 10)(PO(sub 4))(sub 6)F(sub 2) became amorphized at lower dose than Ca(sub 2)La(sub 8)(SiO(sub 4))(sub 6)O(sub 2). However, the critical amorphization dose increased much more rapidly for the former above 350 K than the latter. At 475 K, Ca(sub 10)(PO(sub 4))(sub 6)F(sub 2) required nearly five times of higher dose to become amorphous than Ca(sub 10)La(sub 8)(SiO(sub 4))(sub 6)O(sub 2). Based on the dose-temperature curves, activation energies for the crystal structure recovery process were determined to be 0.07 eV for Ca(sub 10)(PO(sub 4))(sub 6)F(sub 2) and 0.13 eV for Ca(sub 2)La(sub 8)(SiO(sub 4))(sub 6)O(sub 2) respectively. The lower critical amorphization dose and lower activation energy for recovery of Ca(sub 10)(PO(sub 4))(sub 6)F(sub 2) are attributed to the weaker P-O bond and the higher fluorine mobility in the structure.