High-temperature thermoluminescence of anion-deficient corundum and its connection with Ti impurity

Anion-deficient corundum (α-Al2O3-δ) was studied for a possible correlation between the TL yield in the high-temperature peak at 830 K and the contents and transformation of intrinsic defects and impurities. Only 40-60% of TLD-500 detectors based on α-Al2O3-δ were found to have a 830 K TL peak. Increasing the concentration of the titanium impurity from 7·10−4 to 21·10−4 wt% was found to reduce the TL yield in the 830 K peak to an undetectable level. Similar variations of Mg, Si, Ca, Cr and Fe impurity concentrations did not allow us to reveal correlations with the TL yield at 830 K. Nevertheless, the measurements of active center concentrations at step-annealing from 300 to 1400 K suggest that the anion deficiency and related cation interstitials participate, as well as chromium ions, in the formation of the 830 K TL peak. Presumably, UV emission with a maximum at 4.1 eV observed in the 830 K TL peak may be caused by transitions from higher excited states in F+, F or other centers, including impurities and multi-component centers with intrinsic defects.