A STUDY OF PHOTOSTIMULATED THERMOLUMINESCENCE IN C-DOPED ALPHA-AL2O3 CRYSTALS

The effects of ultraviolet light on alpha-Al2O3:C crystals were studied. Thermoluminescence, x-ray-induced luminescence and photostimulated thermoluminescence were investigated. Emission as well as stimulation spectra were measured. Results were compared with those obtained for nominally pure alpha-Al2O3 crystals. The main thermoluminescence and photostimulated thermoluminescence peaks appeared in both types of crystals at the same temperature of 180-degrees-C and with the same thermal activation energy of 1.12 eV. The stimulation spectra of photostimulated luminescence showed a main maximum at 220 nm and weaker maxima at 260 and 300 nm. The 220 and 260 nm maxima have previously been observed in nominally pure alpha-Al2O3 Crystals and have been attributed to F+ absorption bands. The same 325 and 410 nm emission bands appeared in doped and in nominally pure crystals. The 410 nm band was dominant in C-doped crystals, while the 325 nm band was the main one in pure samples. Al2O3:C Crystals which had previously been exposed to ionizing radiation and heated only to 500-degrees-C, were found to be sensitive to extremely low doses of monochromatic near-ultraviolet light. These specimens showed a linear dependence of photostimulated thermoluminescence intensity on the ultraviolet dose over more than four orders of magnitude. Possible applications of photostimulated thermoluminescence in these crystals for ultraviolet dosimetry are discussed.