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    Thermoluminescence properties of Li2B4O7:Cu, B phosphor synthesized using solution combustion technique
    (Pergamon-Elsevier Science Ltd, 2017) Ozdemir, A.; Altunal, V.; Kurt, K.; Depci, T.; Yu, Y.; Lawrence, Y.; Nur, N.
    To determine the effects of various concentrations of the activators copper (Cu) and boron (B) on the thermoluminescence (TL) properties of lithium tetraborate, the phosphor was first synthesized and doped with five different concentrations of copper (0.1-0.005 wt%) using solution combustion method. 0.01 wt% Cu was the concentration which showed the most significant increase in the sensitivity of the phosphor. The second sort of Li2B4O7:Cu material was prepared by adding B (0.001-0.03 wt%) to it. The newly developed copper-boron activated lithium tetraborate (Li2B4O7:Cu, B) material with 0.01 wt% Cu and 0.001 wt% B impurity concentrations was shown to have promise as a TL phosphor. The material formation was examined using powder x-Ray Diffraction (XRD) analysis and Scanning Electron Microscope (SEM) imaging. Fourier Transform Infrared (FT-IR) spectrum of the synthesized polycrystalline powder sample was also recorded. The TL glow curves were analyzed to determine various dosimetric characteristics of the synthesized luminophosphors. The dose response increased in a linear way with the beta-ray exposure between 0.1-20 Gy, a dose range being interested in medical dosimetry. The response with changing photon and electron energy was studied. The rate of decay of the TL signal was investigated both for dark storage and under direct sunlight. Li2B4O7:Cu, B showed no individual variation of response in 9 recycling measurements. The fluorescence spectrum was determined. The kinetic parameters were estimated by different methods and the results discussed. The studied properties of synthesized Li2B4O7:Cu, B were found all favorable for dosimetric purposes.
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    Thermoluminescence properties of non-stoichiometric Li2Si2O5 synthesized from natural amethyst quartz
    (Elsevier Science Bv, 2016) Nur, N.; Guckan, V.; Kizilkaya, N.; Depci, T.; Ahmedova, C.; Ozdemir, A.; Altunal, V.
    In the present study, on the contrary of lots of researches, stoichiometric (s-LD) and non-stoichiometric (n-LD) lithium disilicate polycrystalline were tried to synthesize using easily available and cheap natural amethyst quartz samples collected from Balikesir Dursunbey Turkey as a starting material by the high temperature solid state method. Structure and morphology of s-LD and n-LD were done using XRD, FTIR and SEM, showing the main structure as lithium disilicate for n-LD. The findings showed that n-LD had better crystal structure and gave better TL response, so a detailed investigation on its main dosimetric properties was studied and presented in this paper. The thermoluminescence (TL) glow curve of n-LD consisted of 3 distinguishable peaks and the main peak was stable since TL sensitivity increased only 12% after 2 kGy of high dose exposure. The reusability results showed that TL intensity decreased maximum 21% and 16% for 5 Gy and 50 Gy, respectively after 11 repeated cycles and n-LD had a superlinearity index (g(D)=1.019). The main peak was just 5% faded in 4 weeks. Consequently, n-LD as a phosphor might be used in many fields concerning with the dose range from 0.1 Gy up to 100 Gy. (C) 2016 Elsevier B.V. All rights reserved.