Amorphization of MgAl2O4 spinel using 1.5 MeV Xe+ ions under cryogenic irradiation conditions

Single crystal thin foils of stoichiometric magnesium aluminate spinel (MgAl2O4) were irradiated with 1.5 MeV Xe+ ions at 30 K. Structural evolution during irradiation was monitored in situ by transmission electron microscopy and using selected area electron diffraction. A transition to a metastable crystalline phase was observed at an ion dose equivalent to 4 displacements per atom (dpa) at a depth in the thin foil specimen of 50 nm. The spinel was ultimately rendered amorphous at an ion dose equivalent to 35 dpa at 50 nm foil depth. These results are compared to previous observations of amorphization in single crystal spinel by Yu et al. [Phil. Mag. Lett. 70 (1994) 235].