Accumulation of radiation damage and disordering in MgAlO under swift heavy ion irradiation

Yasuda, Kazuhiro*; Yamamoto, Tomokazu*; Eto, Motoki*; Kawasoe, Shinji*; Matsumura, Sho*; Ishikawa, Norito   

Accumulation and recovery of radiation-induced damage with swift heavy ions instoichiometric magnesium aluminate spinel, MgAlO, has been investigated. Microstructural change and atomic disordering was examined through transmission electron microscopy (TEM) techniques, with bright-field (BF) and high-resolution (HR) TEM images, and high angular resolution electron channelling X-ray spectroscopy (HARECXS), for single crystal MgAlO irradiated with 200 MeV Xe, and 340 or 350 MeV Au ions. The density of core damage region, detected by BFTEM with Fresnelcontrast, increased proportionally with ion fluence at the early stage of accumulation. This result is discussed with a balance between the formation and recovery of the core damage region under irradiation, and the influence region to induce the recovery was evaluated to be 7-9 nm in radius. The structure of the core damage region is found from HR and BFTEM images to be a columnar vacancy-rich region with a low atomic density.