Effects of annealing on the thermoluminescence characteristics of Dy and Tb doped SrSO4 nanophosphor under gamma excitation

The influence of annealing temperatures and different crystallite size the thermoluminescence (TL) properties of SrSO4:Dy,Tb nanophosphor was studied. The SrSO4:Dy,Tb phosphor was prepared by the co-precipitation method. The structural characterizations were analyzed by XRD, composition was investigated by EDX and morphology was determined by SEM technique. The structure of SrSO4:Dy,Tb nanocrystalline powders was an orthorhombic structure with average grain sizes of 52, 57, 70 and 113 nm for 600, 700, 900, and 1000 °C annealing temperatures, respectively. The energy absorption values were calculated by reflectance spectra and the results showed that different annealing temperatures affected the numbers of absorption energy values which was appeared. The absorption energy values were approximately increased by increasing annealing temperature. In the range of 10 Gy-12 kGy, a linear TL dose-response related to the peak with the maximum intensity was observed. The effect of heating rate of 2 and 5 °C/s in TL glow curve have been studied, too. The analysis of the peak temperature values on the glow curves was studied using the computerized glow curve deconvolution (CGCD) method. The results showed the activation energy was between 0.5 and 3.45 and form factor of 0.5 for 900 °C and the activation energy 0.7 and 1.0 and form factor close to 0.5 for 1000 °C annealing temperature. EPR studies were performed to study the defect centers for 900 °C annealing temperature sample.