Thermoluminescence and defect centers in β-CaSiO3 polycrystal

Abstract

β: CaSiO3 polycrystal was synthesized by the devitrification method. The polycrystal exhibits three thermoluminescence (TL) peaks at 124 ºC, 250 ºC and 306 ºC. Electron paramagnetic resonance (EPR) spectroscopy was used to study the defect centers induced in the polycrystal by gamma irradiation and to identify the centers responsible for the TL process. Three defect centers contribute to the observed spectrum at room temperature. Center I with principal g-values 2.0135, 2.0094 and 2.0038 is attributed to O ion and the center appears to be the recombination center for 124 ºC, 147 ºC and 306 C TL peaks. Center II exhibiting an isotropic g-value of 2.00025 is identified as an Fþ-center (singly ionized oxygen vacancy). Fþ-center is also observed to be a recombination center for several TL peaks. Center III is assigned to a Ti3þcenter displaying an orthorhombic g- tensor with principal values g1 ¼1.9830, g2 ¼1.9741 and g3 ¼1.9046. This center is associated with 124 ºC and 147 ºC TL peaks. TL emission spectrum of β-CaSiO3 shows two emission bands at 370 and 520 nm.