Ion-beam induced disordering and onset of amorphization in spinel by defect accumulation

Ion-irradiation induces amorphization in many intermetallics and ceramics, but spinel (MgAl₂O₄) is considered a “radiation resistant” ceramic. Spinel was irradiated with 1.5 MeV Kr⁺ at 20 K and observed in situ by transmission electron microscopy (TEM). The spinel remained crystalline to a high dose of 1 × 10¹⁶ ions/cm², without any evidence of amorphization. Another spinel was preimplanted with Ne (400 keV and 50 keV). The microstructure revealed a still crystalline material with 8 nm interstitial loops. After irradiation with 1.5 MeV Kr⁺ (20 K), amorphization, a result of cation disordering, initiated at a dose of 1.7 × 10¹⁵ ions/cm². At a dose of 1 × 10¹⁶ ions/cm², the spinel was partially amorphous and the remaining crystalline domains disordered. These results show that spinel can be disordered and that amorphization can be triggered by the introduction of stable defects, followed by ion irradiation at low temperature.