Thermoluminescence of α-Al2O3:C,Mg annealed at 1200 °C

Stimulated luminescence in alpha-Al2O3:C,Mg has thus far been studied for samples annealed at temperature no higher than 900 degrees C as can be seen by an examination of the literature. We report the thermoluminescence (TL) features of alpha-Al2O3:C,Mg annealed at 1200 degrees C. A glow curve measured at 1 degrees C/s from the samples annealed at 1200 degrees C shows eight peaks at 54, 80, 102, 173, 238, 290, 330 and 387 degrees C. Kinetic analyses show that the peak at 54 degrees C follows general order kinetics (b = 1.3) whereas the rest follow first order kinetics. The values of the activation energy of the peaks are between 0.77 eV and 1.90 eV and the frequency factors are of the order of 10(10)-10(14) s(-1). The intensity of the peaks at 54, 80, 102 and 173 degrees C increase with heating rate whereas those of the peaks at 238 and 290 degrees C decrease with heating rate. The decrease of intensity of the peaks at 238 and 290 degrees C with heating rate is due to thermal quenching whereas the increase of intensity of the peaks with heating rate indicates an inverse thermal-quenching-like behaviour. Interestingly this behaviour is observed only after annealing at 1200 degrees C. The activation energy for thermal quenching as calculated using the peaks at 238 and 290 degrees C are (1.02 +/- 0.16) eV and (1.33 +/- 0.15) eV respectively. Regarding the dosimetric features, the dose response of the peaks at 54, 80 and 102 degrees C are sublinear within 1-10 Gy and the peak at 54 degrees C saturates above 6 Gy. In contrast, the response of the peak at 173 degrees C is sublinear with 1-4 Gy and superlinear between 4 and 10 Gy. The peaks are found to fade at different rates and the rate of fading is also affected by annealing.