Atomic structure and disordering induced by 350 MeV Au ions in MgAl2O4

Microstructure change and atomic disordering in MgO · nAl₂O₃ (n = 1.1) irradiated with 350 MeV Au ions (S_e = 35 keV/nm) were investigated through transmission electron microscopy (TEM) and high angular resolution electron channeling X-ray spectroscopy (HARECXS) techniques. High resolution TEM revealed that each ion track maintains crystalline structure. The core region of ion track is found to reveal a lattice fringe with a half period of spinel matrix, suggesting the phase transformation from spinel to rock-salt structure. HARECXS analysis clearly showed progress of cation disorder at a significantly large region of 10 nm in diameter. These results are compared with the previous results of 200 MeV Xe ion irradiated spinel (S_e = 25 keV/nm). The structure of ion tracks is found to consist of three concentric circle structures: the defective core region (2 nm in diameter), strained region (5 nm) and cation disordered region (10–12 nm).