Ion irradiation and annealing effects in Al2O3 and MgAl2O4

Abstract In situ observation of structural changes of Al 2 O 3 and MgAl 2 O 4 induced by Xe and He ion irradiations and successive annealing were performed in an electron microscope equipped with ion accelerator. By Xe ion irradiation amorphization occurred in both the materials and bubbles were formed in MgAl 2 O 4 . By He ion irradiation bubbles were formed in both the materials, but amorphization was not observed to a fluence of 1.8 × 10 21 /m 2 (11 dpa). By annealing after the irradiation, bubbles began to grow large by coalescence at 1000°C in Al 2 O 3 , and at 900°C in MgAl 2 O 4 , respectively. Amorphization began to recover in both materials at these temperatures. In the case of MgAl 2 O 4 amorphous region recovers completely to polycrystalline state at 1000°C, and in the case of Al 2 O 3 to original single crystal, respectively. Pit formation and exfoliation also occur in both materials at about 1100°C.