MICROSTRUCTURAL EVOLUTION IN ION-IRRADIATED AND OR ELECTRON-IRRADIATED SINGLE-CRYSTAL AL2O3/

Pure and Cr2O3-doped single crystal alpha-Al2O3 specimens were irradia ted with 330 keV O+-ions, 400 keV He+-ions and 120 keV electrons at te mperatures of 1123 to 1323 K, and the damage structure was studied by transmission electron microscopy. Dislocations, cavities and gamma-Al2 O3 grains recrystallized from alpha-Al2O3 were formed by O-ion irradia tion at 1223 K. The damage region extended to a depth of about twice a s large as the peak damage depth predicted by TRIM85, and cracking occ urred in the deeper part of the region. Recrystallization and cracking were not observed in the specimen irradiated with He-ions up to nearl y the same dose as the case of O-ion irradiation. Instead, dislocation loops and cavities were observed. Damage near surface on basal planes occurred during 120 keV electron irradiation at 1273 K in the He prei rradiated pure Al2O3 specimen.