Thermo-luminescence kinetic parameters of γ-irradiated Sr ₄Al 1₄O2 ₅:Eu²⁺, Dy³⁺ phosphors

In this paper, we present a detailed investigation of the thermo-luminescence (TL) kinetics of the long afterglow phosphor, Sr ₄Al1₄O2₅:Eu²⁺,Dy³⁺, synthesized by the combustion method. Kinetic parameters such as the activation energy (E), the frequency factor (s) and the order of kinetics (b) were calculated using Chen's formulism. The crystalline structure of the phosphor was examined using X-ray powder diffraction and transmission electron microscopy. The average particle size was found to be in the range of 45-52 nm. The optimum dopant concentrations were Eu (1 mol%) and that of Dy (2 mol%). The TL response of the phosphor was monitored after the samples were irradiated with a γ-dose using a ⁶⁰Co source in the 20-800 Gy range. A broad TL peak, (stretching from 328 to 410 K) with a maximum at 368 K was observed. With increasing irradiation dose, the main peak shifts toward higher temperatures. Symmetry factor calculations show that the main TL glow peak obeys second-order kinetics, which could be attributed to the creation of deep level traps. This means that γ-ray irradiation greatly affects the distribution of traps in the Sr₄Al1₄O2₅:Eu²⁺,Dy³⁺ phosphor. The phosphor showed a linear response with γ-dose.