Dosimetric properties of aluminium oxide doped with germanium co-doped with strontium irradiated by cobalt-60 gamma rays

Abstract

The thermoluminescence (TL) properties of powder Al2O3, Al2O3:Ge and Al2O3:Ge;Sr irradiated by Cobalt-60 gamma rays were studied. The TL properties investigated were the minimum detectable dose, glow curve, trap parameters, linearity, sensitivity, thermal fading and reproducibility. Samples were prepared using combustion synthesis technique with various heat treatments to study the influence on the TL response. The physical properties of the samples were determined using X-Ray diffraction (XRD), energy dispersive X-ray field emission scanning electron microscopy (EDX-FESEM) and transmission electron microscopy (TEM). The experiments showed that Al2O3:Ge (3.0%);Sr (0.3%) was the best in terms of TL properties compared to other prepared samples. The annealing procedure of the sample was determined at 400 °C for 1h, followed by 80 °C for 16 h with the heating rate of 3 ºC s-1. Analysis of kinetic parameters showed that the sample possessed second order kinetic characteristics supported by the whole glow peak technique. Its activation energy, obtained by peak shape method was E = 1.37 ± 0.14 eV and its frequency factor, s = 4.70 ± 1.18 x 1017 s?1, however by using initial rise method, E = 1.00 ± 0.01 eV and s = 4.36 ± 1.67 × 1010 s?1. The samples exhibited good sensitivity at high dose (10 – 80 Gy) and low dose (0.5 ? 4.0 Gy) with 52.72 nC mg?1 Gy?1 and 43.40 nC mg?1 Gy?1 respectively. In addition, the linearity of the sample was also good at high dose and low dose with correlation coefficient, R2 of 0.9681 and 0.9961 respectively. The fading was low at high dose (50 Gy) and low dose (4 Gy) with the percentage loss of 33% and 34% after 60 days exposed. Furthermore, it also possessed good reproducibility with the percentage of standard deviation of 2.4% (4 Gy) and 6.5% (50 Gy) with the minimum detectable dose of 0.0065 mGy. The existence of main peaks in XRD pattern, TEM micrographs and the results of EDX-FESEM clarified that the sample was in the nano polycrystalline state with size of 9.36 nm and all the required elements were present in the powder sample. In conclusion, Ge 3.0% mol doped, Sr 0.3 mol% co-doped Al2O3, was found to be a potential material to be used as a TL dosimeter which satisfies most of the desirable TL characteristics.