Optically stimulated luminescence of α-Al2O3:C by the vertical gradient freezing (VGF) method

A highly sensitive α-Al2O3:C crystal was directly grown by the vertical gradient freezing (VGF) method, which combines the advantages of the crystal growth in the highly reducing atmosphere in the presence of graphite and the crystal directly grown by the using Al2O3 and graphite powder as raw materials. The main OSL characteristics of the detectors as grown were investigated. The OSL signal originates from the main TL peak, the responsible electron trap can be emptied basically by OSL readout. The mean OSL sensitivity per unit mass of the VGF α-Al2O3:C is 1.6 times higher than that of the TLD-500K. The OSL detection thresholds of the VGF α-Al2O3:C and the TLD-500K are 0.21 μGy and 0.51 μGy respectively. The OSL signals for the two kinds of detectors are reproducible within a coefficient of variation of less than 2.5% over ten re-use cycles without systematic decrease. The VGF α-Al2O3:C detectors shown an excellent linear response within the dose range from 1 μGy to 15 Gy. The dose can be independently re-analysed multiple times. The VGF α-Al2O3:C can be used to measure the very low dose in environmental monitoring and personnel dosimetry.