Thermoluminescence and electron paramagnetic resonance correlation studies in lithium silicate phosphor

Abstract

Lithium silicate phosphor, synthesized by the solid-state reaction method, displays three thermoluminescence (TL) peaks at 155 °C, 240 °C and 430 °C. Activation energy, frequency factor and kinetic order associated with the TL peaks have been determined using E-Tstop and glow curve deconvolution (GCD) methods. Electron Paramagnetic Resonance (EPR) studies have been carried out to identify the defect centers induced in the phosphor by gamma irradiation and also to find the centers responsible for the TL process in the system. The observed EPR spectrum arises from a superposition of three defect centers. One of the centers (center I) with a g-value 2.0097 is identified as the O− ion. Center II with an isotropic g-value 2.0002 is assigned to a F+-type center (singly ionized oxygen vacancy). The F+ center is likely to be associated with the TL peak at 156 °C. Center III characterized by a rhombic g-tensor with g1 = 1.9831, g2 = 1.9676, and g3 = 1.9208 is identified as a Ti3+ center. The Ti3+ center relates to the low temperature TL peak at 155 °C.