Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

Structural changes in magnesium aluminate spinel (MgO . nAl(2)O(3)) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne+ ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO . Al2O3 has a tendency to form the normal spinel configura tion, where Mg2+ ions and Al3+ ions occupy mainly the tetrahedral and the o ctahedral sites, respectively. Electron irradiation induces simple cation d isordering between the tetrahedral sites and the octahedral sites in MgO . Al2O3 In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO . Al2O3 irradiated with Ne+ ions. In contrast, cation disordering i s suppressed in MgO .2.4Al(2)O(3) irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effect ive in promoting irradiation damage recovery through interstitial-vacancy r ecombination. (C) 2000 Elsevier Science B.V. All rights reserved.