Irradiation

Analytical Chemistry (journal)

Physics

Luminescence

Neutron

Composite material

Organic chemistry

Nuclear physics

Chemistry

Metallurgy

Materials science

Fluence

Neutron temperature

Corundum

Annealing (glass)

Dimer

Chromatography

Optoelectronics

Crystallography

Journal of Nuclear Materials

The precise study of the thermal annealing of the F2-type dimer defects, being under discussion in the literature for a long time and responsible for the number of absorption bands below 4.5 eV, has been performed in corundum single crystals irradiated by fast neutrons with a fluence of 6.9 × 1018 n/cm2. The Gaussian components of the radiation-induced optical absorption with the maxima at 4.08, 3.45 and 2.75 eV have been considered as a measure of the F2, F2+and F22+centers, respectively. In contrast to the F and F+ centers, the concentration of which continuously decreases at the sample heating up to 1100 K, the concentration of dimer defects with different charge states passes the increasing stages above 500 K starting from the F22+centers. The tentative mechanisms of such rise of the F22+centers as well as of the subsequent transformation/rise of dimer centers, F22+→F2+→F2at 650-800 K are considered. The possible sources of carriers needed for the recharging of dimer centers are also analysed on the basis of thermally stimulated luminescence measurements up to ~850 K.

Thermal annealing and transformation of dimer F centers in neutron-irradiated Al2O3 single crystals