Radiation damage of α-Al2O3 in the HVEM. I

The temperature dependence of the apparent displacement threshold energy has been measured for single crystal α-Al2O3 in a high voltage electron microscope, over the temperature range 320-1120 K. Below 570 K the threshold energy for observable damage remains constant at 390 +- 10 keV, then rises to a peak of 440 +- 20 keV at 695 K followed by a rapid fall to approximately 200 keV at 870 K and above. Measurement of the displacement threshold energy, using the optical absorption and luminescence of oxygen and aluminium electron irradiation induced vacancies at several temperatures, gives a value of 400 +- 25 keV for the oxygen ion and 175 +- 25 keV for the aluminium ion. These results show that oxygen and aluminium ions have widely different displacement energies, Esub(d), of approximately 75 and 18 eV respectively. (Auth.)