Browsing by Author "Altunal, V"

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    Luminescence characteristics of Al-and Ca-doped BeO obtained via a sol-gel method
    Altunal, V; Guckan, V; Ozdemir, A; Can, N; Yegingil, Z
    BeO, BeO:Al-1%, BeO:Ca-1%, and BeO:Al-1%, Ca-0.1% ceramics were synthesized by the sol-gel method. The X-ray luminescence was studied, and broad emission peaks located at 230 nm (similar to 5.4 eV) and 300 nm (similar to 4.1 eV) were observed. We investigated thermoluminescence peaks contributing to optically stimulated luminescence (OSL) signals for the ceramics. The thermal quenching of the OSL signals was evaluated, and the quenching energies were estimated as between approximately 0.5 eV and approximately 0.7 eV. To check the feasibility for dosimetry purposes, the dose response, reusability, and dark storage fading of the OSL signals were investigated. The dose response was observed to be linear between 0.1 and 100 Gy. The minimum detectable doses of BeO, BeO:Al-1%, BeO:Ca-1%, and BeO:Al-1%, Ca-0.1% were estimated as approximately 0.9 mGy, approximately 4 mGy, approximately 0.5 mGy, and approximately 0.5 mGy, respectively. Very good reusability was observed over ten cycles, with a maximum deviation of 2%. The results obtained from BeO:Al-1%, Ca-0.1% could be useful for OSL dosimetry, particularly in medical applications.
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    Characterization and some fundamental features of Optically Stimulated Luminescence measurements of silver activated lithium tetraborate
    Ozdemir, A; Altunal, V; Guckan, V; Can, N; Kurt, K; Yegingil, I; Yegingil, Z
    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 similar to 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 degrees 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.