Optically Stimulated Luminescence (OSL) dosimetric properties of Li2B4O7:Ag,Gd and its relationship with thermoluminescence (TL) glow-curves

Abstract

The aim of this work was to develop a new lithium tetraborate luminophore with impurities that are strong co-activators for Optically Stimulated Luminescence (OSL) and to investigate its dosimetric properties using OSL method. Li2B4O7:Ag,Gd phosphor consisting of polycrystalline powder was synthesized using Solution Combustion Synthesis method. The structural characterization of the synthesized phosphor was performed using X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) methods. OSL dosimetry properties as a function of step-annealing procedure, radiation dose response, reproducibility of response and loss of stored signal in dark were investigated. Thermoluminescence (TL) glow curve of Li2B4O7:Ag,Gd phosphor consists of two separated glow peaks located at ∼80 and ∼210 °C with a heating rate of 2 °C/s. The traps responsible for these two TL peaks in Li2B4O7:Ag,Gd phosphor were found to be optically sensitive. Li2B4O7:Ag,Gd exhibits high OSL sensitivity and a good OSL signal reproducibility to ionizing radiation. The beta dose-response was performed in the range from 0.1 Gy to 500 Gy. The time-integrated total OSL signal intensity increases linearly with increasing dose from ∼6 Gy to 500 Gy. The minimum detectable dose was found to be ∼17.1 ± 0.9 μGy. The stored energy increased ∼6 % within 4 weeks following a strong fading value of 27 % of the initial OSL intensity after 24 h. Indeed, the X-ray Luminescence (XL) emission spectra are the characteristic of the expected f-f transitions. Luminescence spectrum of Gd doped Li2B4O7 exhibits major red emissions (590 nm, 607 nm, 621 nm) and a weak blue emission (450 nm) along with the emission bands from undoped Li2B4O7. These results strongly suggest that the luminescence properties of Li2B4O7:Ag,Gd deserves more attention as possible dosimeter material. Explanations of many TL/OSL phenomena observed in the study of Li2B4O7:Ag,Gd phosphor and improvements based on the better knowledge in the mechanism of TL/OSL in Li2B4O7:Ag,Gd, a boron-based compound were achieved by this study.