Calculation of thermal quenching parameters in BeO ceramics using solely TL measurements

摘要

The decrease of the luminescence efficiency with increasing temperature is known as the thermal quenching effect. Various materials exhibit thermal quenching, among which quartz and Al2O3:C stand as the mostly well known. BeO, which is used generally as OSL dosimeter, has been reported to undergo thermal quenching effect; so far in the literature only one thermal quenching parameter was determined using various OSL techniques. This study is the first attempt in the literature to calculate both W and C thermal quenching parameters. TL glow curves of BeO ceramic chips were studied as a function of heating rates ranging between 0.25 K/s and 8 K/s. The procedure of analysis includes various steps dealing with de convolution of the quenched TL glow curves, correction for temperature lag, evaluation of the experimental thermal quenching parameter values, reconstruction as well as de-convolution of the reconstructed TL glow curves. The reconstruction step is really important, while its aim is twofold: (a) to provide the most stringent criterion for selecting the physically meaningful W,C values for BeO and (b) to check the kinetic parameters of the unquenched glow curve. The first peak of BeO is not affected by the thermal quenching, while both second and third peaks suffer from thermal quenching. Wand C parameters were determined as 0.54-0.66 (+/- 0.07) eV . 10(5)-2.4 . 10(6) (+/- 4 . 10(5)) for peak 2 and 0.74-0.86 eV and 2.8 . 10(6)-2.1 . 10(7) for peak 3 respectively for U-340 filter by using indirect fit method. The same process was applied for BG-39 filter and W and C parameters were compared to those found through U-340 filter. The values for the main dosimetric peak 2, are independent on the detection filter used, as well as in great agreement with the W values previously reported in the literature. The difference in the W, C parameters for those two peaks in BeO provide a strong argument to the fact that each one of these two peaks uses different recombination centers. According to the results of the de-convolution before and after the reconstruction, it is indicated that the influence of the thermal quenching is mainly reflected to the value of the activation energy for the case of peak 3, which is under-estimated without reconstruction. (C) 2017 Elsevier Ltd. All rights reserved.