Thermoluminescence and optically stimulated luminescence of α-Al₂O₃ with different carbon concentrations

Abstract

Carbon-doped α-Al₂O₃ (α-Al₂O₃:C) single crystals (nominal carbon concentrations with 500, 1000, 1500 and 2000 ppm) were grown by the vertical gradient freezing (VGF) method. Thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of as-grown α-Al₂O₃:C crystals were studied. F and F⁺ center absorption (except for the sample with 500-ppm carbon) at 205 and 256 nm was enhanced with increasing carbon concentration. The results show that TL and OSL intensities from α-Al₂O₃:C are strongly correlated with the ratio of absorption coefficients from the F-center to the F ⁺-center. Both TL and OSL intensities of the sample doped with 1000 ppm reach maximum when the ratio of absorption coefficients from the F-center to F ⁺-center is at its highest. The OSL response of the sample doped with 1000 ppm carbon is 3.43 times that of the sample doped with 500 ppm carbon and is 2.47 times higher than that of the TLD-500 K. The activation energies for samples with 500, 1000, 1500 and 2000 ppm carbon were calculated as 1.33 ± 0.11, 1.58 ± 0.02, 1.52 ± 0.02 and 1.52 ± 0.04 eV, respectively. The OSL intensities from α-Al₂O₃:C appear strongly correlated with the ratio of absorption coefficients F-center to F ⁺-center. These attractive features may pave the way for the VGF method to improve the luminescence and dosimetry properties.

KEYWORDS:

• Α-Al₂O₃:C
• thermoluminescence
• optically stimulated luminescence
• vertical gradient freezing method

Disclosure statement

No potential conflict of interest was reported by the author(s).