Characterization and some fundamental features of Optically Stimulated Luminescence measurements of silver activated lithium tetraborate

Abstract

A new lithium tetraborate (Li2B4O7 or abbreviated as LTB) material was produced by adding various concentrations of Ag impurities to allow better luminescent properties using the solution combustion synthesis (SCS) method. The formation of single phase LTB was confirmed using X-ray Diffraction (XRD) data and Scanning Electron Microscopy (SEM) analysis indicated the existence of a tetragonal crystalline domain. Two broad band emissions located at ∼ 272 nm (near UV region) and 526 nm (green region) were observed from room temperature photoluminescence (PL) under 205 nm excitation The synthesized material consisted of polycrystalline LTB with 1 wt% Ag (abbreviated herein as LTB:Ag) exhibits considerable thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) which is several times more sensitive to beta radiation than the other concentrations attempted. It was determined that the OSL signal has been a collection of three component signals. A step-preheating procedure to investigate the depth of the trapping centers associated with the OSL signal was carried out. We suggest that the TL peak at 200 °C mainly contributes to the OSL signal. It was observed that the total OSL area shows a linear dose response for beta doses ranging from 1 to 100 Gy. The minimum detectable dose (MDD) value was found to be around 3 mGy using the total OSL area. Under optimum conditions (irradiation with beta-rays), the reproducibility of total OSL area was determined with a −3% deviation at the end of the 9th irradiation-blue light stimulation-readout cycle. The dark storage stability of the total OSL signals was investigated and fading of the total OSL area was found to be approximately 25% after one week. The trap depth corresponding to the OSL signal was found to be 0.99 eV and 0.94 eV using various heating rate and isothermal annealing methods, respectively. Finally, silver doped lithium tetraborate is shown to have promise as an optically stimulated luminescent dosimeter, particularly in medical and personal applications.