Ion-beam-induced spinel-to-rocksalt structural phase transformation in MgAl2O4

An ion-beam-induced metastable phase in magnesium aluminate spinel (MgAl2O4 ) has been examined in detail using transmission electron microscopy. Singl e crystals of MgAl2O4 with (111) orientation were irradiated with 180-keV N e+ ions at 120 K to fluences of 10(16) and 10(17)/cm(2). Selected-area elec tron diffraction patterns obtained from the irradiation-induced damaged lay er revealed that all even hkl reflections (e.g., 222) possess strong intens ity, while all odd hkl reflections (e.g., 111) are weak. The features of th ese diffraction patterns corresponded to those of the rocksalt (NaCl) struc ture, suggesting that an ordered spinel to disordered rocksalt structural p hase transformation in MgAl2O4 was induced by ion beam irradiation. (C) 200 0 American Institute of Physics. [S0003-6951(00)00317-X].