Thermoluminescence and radioluminescence of alexandrite mineral

The thermoluminescence (TL) of natural alexandrite (BeAl2O4) was investigated using different methods, namely T-m-T-stop, T-m as a function of beta irradiation dose, glow curve best fitting, variable heating rate, and TL fading as a function of time after irradiation, in addition to radioluminescence (RL) measurements under X-ray excitation as a function of the temperature. The chemical composition and the concentration of secondary mineral phases were determined by scanning electron microscopy and Energy-dispersive X-ray spectroscopy. TL measurements with heating rate = 1 K/s revealed five individual TL peaks at about 355 (peak I), 405 (peak II), 435 (peak III), 530 (peak IV), and 580 K (peak V). The activation energy E and the frequency factor s associated with each of them were determined by different methods. Within irradiation doses from 1 to 10 Gy, analysis of the T-m position indicated that all glow peaks exhibited a first-order kinetics TL mechanism. TL fading at room temperature was 15% for peak IV and 5% for peak V within 2 days after irradiation. RL measurements revealed luminescence centers attributed to Cr3+, Mn4+ and Fe3+ impurities. Overall, the results suggest that natural alexandrite has a potential use in dosimetry.