Thermally Stimulated Luminescence and Exoelectron Emission Mechanism of the 430 K (D') Dosimetric Peak of alpha-Al2O3

Several alpha-Al2O3 samples were studied in order to determine the mechanism of electron-hole processes of the 430 K (D') thermoluminescence (TL) and thermally stimulated exoelectron emission (TSEE) dosimetric peak. Single crystals prepared in highly reducing conditions were treated in different atmospheres (reducing/oxidizing) and their optical absorption (after isochronous annealing), fluorescence and TL properties were investigated. From these results an electron trap is suggested for the 430 K peak which is in contradiction to some data taken from the literature: this problem is then discussed. Pure and Th4+ doped alpha-Al2O3 powders were studied by TL methods regarding doping concentration and preparation conditions. In this way the role of aluminum vacancies is proved. Considering these new results, literature data and different hypotheses, the possible nature of the trap is discussed.