Annealing process of F- and F+-centers in Al2O3 single crystal induced by fast neutrons irradiation

F and F+ centers were produced in Al2O3 single crystal by fast neutrons (En > 1.2 MeV) irradiation at low fluence (4.4 × 1016 n cm−2). The evolution of defects intensity as a function of temperature and of time at 493, 623 and 823 K was investigated by UV-visible spectrophotometry technique. It can be concluded from the analysis of isochronal and isothermal annealing data, that the F- and F+-centers annealing process is complex. At low annealing temperature (<473 K), only F- to F+-center conversion process takes place. At higher temperature (>493 K) the annealing is due to the superposition of several mechanisms with different activation energies. According to our results, the activation energies needed for both F- and F+-centers elimination are 0.2, 0.3 and 0.03 eV for temperature range of 300-673 K, 673-873 K and >873 K, respectively.