Thermoluminescence from Cu Doped Lithium Tetraborate Irradiated with X-ray and γ Using 137Cs Radioactive Source

Lithium tetraborate (Li2B4O7) pellets prepared by using water/solution assisted method were synthesized and characterized. Copper was used as doping material in order to enhance the Li2B4O7 thermoluminescent properties. For synthesis heating temperature parameters were defined at 750 degrees C for 2 hr, followed by 150 degrees C for another 2 hr. The materials were produced at five different Cu concentrations: 0.02, 0.04, 0.06, 0.08, and 0.1 wt%. The luminescent and morphological characterizations were performed by X-ray diffraction (XRD), Scanning electron microscope (SEM), Photoluminescence (PL), and Ultraviolet-visible spectroscopy (UV-Vis). XRD and SEM analysis of intrinsic and doped materials confirmed the obtained Li2B4O7 structure and show its morphology. XRD patterns of the Li2B4O7 matched a tetragonal crystal structure. Crystals of Li2B4O7 of an average size of 50 nm were obtained. The presence of the copper dopant was confirmed in crystals of Li2B4O7:Cu by SEM-EDS (energy dispersive spectroscopy X-ray). The emission spectrum of Cu doped Li2B4O7 showed a prominent peak at 367 nm, while the main UV-Vis absorption was observed from 240 nm to 300 nm due to Cu+ ion 3d(10) -> 3d(9) 4s transitions. The thermoluminescent (TL) response was studied for both gamma radiation and X-ray. A 661.7 keV gamma radiation using a Cs-137 source at doses of 50, 100, 200, 300, 400 and 500 mGy was applied to Li2B4O7:Cu (0.1 wt%) pellets. An X-ray source was used at doses of 600, 800 and 1000 mGy to irradiate pellets of Li2B4O7:Cu (0.02, 0.04, 0.06, 0.08 and 0.1 wt%). A linear TL response was observed for both X-ray and gamma radiation. The kinetic parameters were calculated using the peak shape method for the Li2B4O7:Cu (0.1 wt%).