Browsing by Subject "Variable heating rates"

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    Cathodoluminescence and thermoluminescence of ZnB2O4:Eu3+ phosphors prepared via wet-chemical synthesis
    (Elsevier Ltd, 2019) Dogan T.; Tormo L.; Akca S.; Kucuk N.; Guinea J.G.; Karabulut Y.; Ayvacikli M.; Oglakci M.; Topaksu M.; Can N.
    In present work, a series of Eu doped zinc borate, ZnB2O4, phosphors prepared via wet chemical synthesis and their structural, surface morphology, cathodoluminescence (CL) and thermoluminescence (TL) properties have been studied. Phase purity and crystal structure of as-prepared samples are confirmed by X-ray diffraction measurements (XRD) and they were well consistent with PDF card No. 39-1126, indicating the formation of pure phase. The thermoluminescence (TL) behaviors of Eu activated ZnB2O4 host lattice are studied for various beta doses ranging from 0.1 to 10 Gy. The high-temperature peak of Eu activated sample located at 192 °C exhibited a linear dose response in the range of 0.1–10 Gy. Initial rise (IR) and peak shape (PS) methods were used to determine the activation energies of the trapping centres. The effects of the variable heating rate on TL behaviour of Eu activated ZnB2O4 were also studied. When excited using an electron beam induced light emission (i.e cathodoluminescence, CL) at room temperature (RT), the as-prepared phosphors generate reddish-orange color due to predominant emission peaks of Eu3+ ions located at 576–710 nm assigned to the 5D0→7FJ (J=1,2,3, and 4) transitions. The maximum CL intensity for Eu3+ ions at 614 nm with transition 5D0→7F2 was reached Eu3+ concentration of 5 mol%; quenching occurred at higher concentrations. Strong emission peak for Eu3+ ions at 614 nm with transition 5D0→7F2 is observed. The CL experimental data indicate that ZnB2O4:Eu3+ phosphor as an orange-red emitting phosphor may be promising luminescence materials for the optoelectronic applications. © 2018 Elsevier Ltd and Techna Group S.r.l.
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    Thermoluminescence behaviour of europium doped magnesium silicate after beta exposure
    (Elsevier B.V., 2020) Uçar Z.G.P.; Kaynar Ü.H.; Dogan T.; Souadi G.O.; Ayvacikli M.; Canimoglu A.; Topaksu M.; Can N.
    This article presents a detailed analysis of beta ray exposed thermoluminescence response of a series of Eu3+ doped (0.5–10 mol%) Mg2SiO4 nanocrystalline samples successfully synthesized through solid state reaction method. Optimizing the doping concentration of Eu3+ ion in Mg2SiO4 phosphor was found as 3 mol%. Two main peaks were seen at 246 °C and 374 °C and also low temperature peak at 78 °C. The intensities of these peaks were increased linearly with increasing beta absorbed dose. Tm−Tstop method was used to reveal trap levels. Variable heating rate and computerized glow curve deconvolution methods were also used to evaluate the number of peaks and kinetic parameters, namely activation energy and frequency factor. The results of a series of experiments carried out to investigate some fading characteristics of Mg2SiO4:Eu3+ were also presented. The findings suggest that thermoluminescence properties of Mg2SiO4:Eu3+ makes this material suitable and promising dosimetric phosphor material for medical applications. © 2020 Elsevier B.V.
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    Thermoluminescence properties of beta particle irradiated Ca3Al2O6 phosphor relative to environmental dosimetry
    (Elsevier B.V., 2020) Bakr M.; Portakal-Uçar Z.G.; Yüksel M.; Kaynar Ü.H.; Ayvacikli M.; Benourdja S.; Canimoglu A.; Topaksu M.; Hammoudeh A.; Can N.
    Undoped Ca3Al2O6 phosphor was successfully synthesized through a gel-combustion method using different fuels. It was characterized by X-ray diffraction (XRD) technique and its cubic phase structure was confirmed from XRD pattern. TL data were recorded from room temperature (RT) to 500 °C in the heating rate of 2 °C/s. The glow curves of Ca3Al2O6 sample exposed to different beta doses (0–200 Gy) exhibited a significant glow peak at about 184 °C. The TL intensity of the glow peak exhibited very good linearity between 0.1 and 10 Gy. Following this, it was decreased at higher doses which was referred to this effect as monotonic dose dependence. Initial rise (IR), peak shape (PS), and variable heating rate (VHR) methods were used to estimate trapping parameters. Computerized glow curve deconvolution (CGCD) method via TLAnal software was also applied to estimate the number of peaks and kinetic parameters corresponding to the main glow curve in Ca3Al2O6 sample. The trapping activation energy of the main dosimetric peak was calculated to be around 1.30 eV for all methods. Present findings confirm that Ca3Al2O6 host is a promising candidate for applications in environmental dosimetry as one depicts good TL dose response with adequate sensitivity and linearity. © 2020 Elsevier B.V.
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    Thermoluminescence glow curves of beta irradiated NaBaBO3: Ce3+ phosphor synthesized by combustion method
    (Elsevier B.V., 2020) Oglakci M.; Topaksu M.; Can N.
    NaBaBO3 samples incorporated with various concentration of Ce3+ were prepared by combustion method. The influences of rare earth doping in synthesized samples were analyzed by X-ray diffraction (XRD). Optimum doping concentration of NaBaBO3:Ce3+ is 0.5 %. Thermoluminescence (TL) kinetic analysis using Tm-Tstop, initial rise (IR), variable heating rate (VHR) and glow curve deconvolution (GCD) methods were performed on the glow curves of NaBaBO3:Ce3+ phosphor material. The Tm-Tstop analysis revealed that the whole glow curve measured without preheat of the prepared sample is composed of at least six overlapping glow peaks. The number of the glow peaks required to provide best fit to the glow curves of the sample are also estimated using GCD method and one found six glow peaks at all doses (FOM ≤ 1.84 %), which are similar to those from Tm-Tstop analysis. The dose response of NaBaBO3:Ce3+ phosphor sample exposed to beta irradiation is linear up to 10 Gy. The results from experiments indicates that main dosimetric peak of NaBaBO3:Ce3+ follows first order kinetic model, which was also supported by dose response plot. The Z effective value of this phosphor is calculated to be 46.66. Present findings confirm that NaBaBO3:Ce3+ phosphor sample is a promising candidate for applications in environmental dosimetry as one depicts good TL dose response with adequate sensitivity and linearity. © 2020 Elsevier B.V.
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    Thermoluminescence study and evaluation of trapping parameters of samarium doped barium silicate phosphor
    (Taylor and Francis Ltd., 2021) Alajlani Y.; Oglakci M.; Kaynar U.H.; Ayvacikli M.; Portakal-Uçar Z.G.; Topaksu M.; Can N.
    We report the detailed analysis of thermoluminescence (TL) glow curves and the evaluation of kinetic parameters of Sm3+-incorporated BaSi2O5.The effect of various heating rates on TL kinetics and glow peak temperatures of Sm3+-doped BaSi2O5 phosphors exposed to beta particle irradiation at room temperature are investigated. The glow curve of the phosphor exposed to β-irradiation consists of two main peaks with maxima at about 91°C and 193°C and exhibits good linearity between 1 and 10 Gy. The activation energies and frequency factors of trap centers involved in the TL emission were calculated from the TL glow curve of the sample by means of variable heating rate (VHR), repeated initial rise (RIR), and computerized glow-curve deconvolution (CGCD). Analysis of the main dosimetric peak techniques indicate that activation energies (E) and pre-exponential factor (s) vary between 0.93 and 1.72 eV, 1010 and 1013 s−1. It is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases. The behavior of the TL intensities and glow peak temperatures as a function of the heating rate are discussed with regards to thermal quenching. © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of The Korean Ceramic Society and The Ceramic Society of Japan.
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    Thermoluminescence study and trapping parameters of beta irradiated NaBaBO3:Gd3+ phosphor
    (Elsevier B.V., 2021) Oglakci M.; Topaksu M.; Souadi G.; Can N.
    A series of Gd3+ doped NaBaBO3 phosphors were synthesized via a combustion approach. The TL data collected by means of a combination of a commercial SCHOTT BG39 and HC414/46 filters was studied to evaluate basic kinetic parameters. Tm-Tstop and, various heating rate (VHR) and computerized glow-curve deconvolution analyses were utilized to analyze collected data. Our findings indicate that luminescence process in scrutinized material may obey first-order kinetics because no shift in the experimental TL glow curves with increased dose was observed. The TL dose response of the TL glow peaks exhibited a linear characteristic up to 20 Gy. The Tm-Tstop method revealed that the number of the component TL glow peaks in the complex glow curve with and without preheating process consisted of six well-isolated and three overlapping glow peaks, respectively. The number of peaks obtained by deconvolution was perfectly matched with those obtained by Tm-Tstop and the figure of merit (FOM) values with and without preheating were 0.84% and 1.48%, respectively. The activation energy value found for the peak at 312 °C using the various heating rate (VHR) method was very close to those of deconvolution method. The total loss of response of TL glow curve sensitivity was much less (only ± 2%) after 10 cycles of reuse. © 2021 Elsevier B.V.
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    Thermoluminescence glow curve analysis and evaluation of trapping parameters of dysprosium doped lanthanum calcium borate La2CaB10O19
    (Elsevier B.V., 2021) Bulcar K.; Oglakci M.; Kaynar U.H.; Ayvacikli M.; Souadi G.; Topaksu M.; Can N.
    The present work elucidates thermoluminescence study of Dy activated lanthanum calcium borate (La2CaB10O19) phosphors and determination of trapping parameters. Two glow curves located at 132 and 295 °C were observed and showed a linear TL response. The kinetic parameters of the glow peaks were evaluated using variable heating rate, repeated initial rise method and Computerized Glow Curve Deconvolution. Analysis of the main dosimetric peaks reveals that the values of the activation energy and pre-exponential factor are found to be 0.78–1.145 eV and 8.59 × 109–8.44 × 1011 s−1, respectively. The sample doped with 1% Dy3+ exhibits a good stability for the reusability. Besides, the found results indicate that the temperature maximum shifts to the higher temperature side as the heating rate increases. Contrary to previously expressed theoretical expectations, anomalous heating rate dependence was observed in Dy3+ doped La2CaB10O19 sample and a semi-localized transition model explaining the anomalous heating rate effect was employed. © 2020 Elsevier B.V.
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    Thermoluminescence glow curve analysis and kinetic parameters of Dy-doped BaSi2O5 phosphor
    (Editorial Office of Chinese Rare Earths, 2022) Alajlani Y.; Can N.
    In this paper, Dy3+ incorporated BaSi2O5 phosphors were synthesized by gel combustion method and characterized by X-ray diffraction (XRD). The effects of various heating rates on thermoluminescence (TL) kinetics and glow peak temperatures of Dy3+ incorporated BaSi2O5 phosphors exposed to β irradiation at room temperature were investigated. The glow curves of the phosphor exposed to β-irradiation (0.1–100 Gy) consist of four main peaks located at 87, 130, 271, and 327 °C and exhibit a good linearity between 0.1 and 100 Gy. Three experimental techniques including variable heating rate (VHR), repeated initial rise (RIR), peak shape (PS) and computerized glow curve deconvolution (CGCD) were employed to determine TL kinetic parameters. Our findings indicate that the TL glow peaks of the phosphor obey first-order kinetics. Analysis of the main dosimetric peaks through the techniques mentioned above indicates that activation energies (E) and pre-exponential factor (s) are in the range of 0.80–1.50 eV and 1.15 × 108–3.28 × 1013 s−1. Additionally, it is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases. The effect on the TL intensities and glow peak temperatures of the heating rate is discussed in terms of thermal quenching. © 2020 Chinese Society of Rare Earths