TL and EPR characteristics of SrAl₂O₄ phosphor prepared by solid-state reaction method

SrAl₂O₄ phosphor was prepared by solid-state reaction method and characterized using X-ray diffraction (XRD), thermoluminescence (TL) and electron paramagnetic resonance (EPR) spectroscopy. TL glow curve of irradiated phosphor shows three peaks at 135, 260 and 350 °C. The order of kinetics of the three TL peaks is second order with an activation energy of 1.05, 1.60 and 1.93 eV, respectively. EPR studies have been carried out to identify the defect centers induced by gamma irradiation and also to identify the defect centers involved in the TL process in SrAl₂O₄. Two distinct centers contribute to the observed spectrum at room temperature. Center I exhibiting a four-line hyperfine splitting is identified as an O⁻ ion. O⁻ ion is associated with the high temperature TL peaks at 260 and 350 °C. An eight-line spectrum with a g-value of 2.0068 is attributed to a F⁺ center (singly ionized oxygen vacancy). This center relates to the 135 °C TL peak.