Amorphization behaviors in polycrystalline alumina irradiated with energetic iodine ions

A cross-sectional transmission electron microscopy (XTEM) technique utilize d in examining the sintered alumina (Al2O3) sample irradiated by 85.0 MeV i odine ions I7+ to 2.8 x 10(18) m(-2) reveals that almost complete amorphiza tion lakes place up to depths around 2 mu m. Several grains including grain s about to be fading out at depths of 2.5-3.5 mu m are seen to have moved f rom the yet-amorphized region leaving the amorphized region behind. The amo rphized regions extend up to depths around 4.5 mu m for the sample irradiat ed to 12 x 10(18) m(-2). Any defect clusters cannot be observed in grains l ocated at depths around 8 mu m, where nuclear energy depositions are predic ted to peak to about 1 dpa. The present results clearly demonstrate that th e energy depositions through electronic process in alumina irradiated with heavy ions like present I7+ transform the crystalline phase into amorphous ones even near room temperatures, for accumulated electronic energy deposit ions above some 1.5-2 GGy with deposition rates above 4-5 keV/nm/ion. (C) 2 000 Elsevier Science B.V. All rights reserved.