Main Glow Peak Research Articles

Dosimetric properties of Tm2O3-doped Ca2BO3Cl

In this work, we prepared Ca2BO3Cl with various amounts (0.1%–1.0%) of Tm2O3 by conventional solid-state reaction and investigated the dosimeter properties. Scintillation peaks at 370, 455, 470, and 650 nm that were derived from the 4f→4f transition of Tm3+ appeared in the X-ray induced scintillation spectra, and the highest scintillation intensity was detected from the 0.5% Tm2O3-doped Ca2BO3Cl. Furthermore, the Tm2O3-doped Ca2BO3Cl exhibited a thermally-stimulated luminescence (TSL) with a main glow peak at 300 °C, and the fabricated Tm2O3-doped Ca2BO3Cl exhibited a linear response in the 0.1–1000 mGy range. In addition, the TSL spectra confirmed that a final luminescence process for the TSL was the 4f→4f transition of Tm3+. In addition to TSL, optically-stimulated luminescence that was attributable to the 4f→4f transition of Tm3+ was recorded under 520 nm light, and the lowest detectable limit was about 1 mGy.

Thermoluminescence kinetic parameters of beta irradiated the zinc gallate phosphor using different methods

The ZnGa2O4 phosphor material was synthesised through the gel combustion method, and its structural characteristics were studied via X-ray powder diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). The XRD result indicates the generation of ZnGa2O4 in spinal cubic phase with a 25 nm crystalline size. The synthesized phosphor was irradiated using a90Sr/90Y source with a dose range of 0.1 Gy–100 Gy. For measuring thermoluminescence (TL), a linear heating rate of 2 °Cs−1 was applied to the sample in a temperature range of 25 °C–450 °C. The TL experiment revealed two peak maxima located at 180 °C and 304 °C and a shoulder around 70 °C. By preheating at 110 °C, the low temperature peak at 70 °C is removed. Both the depth and frequency factors of electron traps were determined using various heating rates (VHR), Tm-Tstop combined with initial rise (IR), and Computerised Glow Curve Deconvolution (CGCD). In both the Tm-Tstop and CGCD methods, six overlapping glow peaks were detected below the main glow peaks. The calculated activation energy values and peak maximum temperatures agree well with each other. The depths of electron traps calculated by different methods were found to be between 0.4 and 1.4 eV. We observed that both peak maximum temperatures and the area under glow peaks gradually decreased with an increase in the heating rate. Both Peak 1 and Peak 2 show sublinear relationship between 0.1-5Gy and 10–100 Gy. The findings of the present study show that the phosphors can serve as effective TLDs.

Effect of Mg on the Structural, Optical and Thermoluminescence Properties of Li3Al3(BO3)4: Shift in Main Glow Peak

The doping of magnesium on lithium aluminium borate phosphor is reported in this study. A solid-state sintering technique was employed as the borate samples were synthesized. This report focuses on the structural, optical, thermoluminescence, and kinetic analyses of the main glow peak. The structural properties of lithium aluminium borates improved due to the magnesium dopants used. Differences in the crystallite size and particle size were 38.85-67.35 nm and 50-60 nm, respectively, and these results were obtained from the analyzed X-ray diffractogram and scanning electron spectroscopy. The energy band gaps obtained from the direct transition of borate phosphor materials were within the range of 3.00-4.40 eV, and the doped samples gave a higher energy band gap. A decrease in the TGA (%) exhibited a weight loss or water loss for the undoped, 0.1% Mg, and 0.3% Mg-doped lithium aluminium borate materials. The glow curve measured at a heat rate of 1 °C·s-1 after irradiation to 50 Gy revealed four peaks related to the magnesium doped lithium aluminium borate. The main glow peak was observed at 86 °C. Activation energy was extracted from the main glow peak by using kinetic analysis which involves the initial rise, deconvolution, and variable heating rate approach, and it was approximately 0.67 ± 0.03 eV. A shift in the main glow peak curve from 86 to 110 °C was recognized for the magnesium-doped lithium aluminium borate when it was irradiated from 1 to 300 Gy.

Basic Characteristics of Dose Distributions of Photons Beam for Radiotherapeutic Applications Using YAG:Ce Crystal Detectors.

Thermostimulated luminescence (TSL) dosimetry is a versatile tool for the assessment of dose from ionizing radiation. In this work, the Ce3+ doped Y3Al5O12 garnet (YAG:Ce) with a density ρ = 4.56 g/cm3 and effective atomic number Zeff = 35 emerged as a prospective TSL material in radiotherapy applications due to its excellent radiation stability, uniformity of structural and optical properties, high yield of TSL, and good position of main glow peak around 290-300 °C. Namely, the set of TSL detectors produced from the YAG:Ce single crystal is used for identification of the uniformity of dose and energy spectra of X-ray radiation generated by the clinical accelerator with 6 MV and 15 MV beams located in Radiotherapy Department at the Oncology Center in Bydgoszcz, Poland. We have found that the YAG:Ce crystal detects shows very promising results for registration of X-ray radiation generated by the accelerator with 6 MV beam. The next step in the research is connected with application of TSL detectors based on the crystals of much heavier garnets than YAG. It is estimated that the LuAG:Ce garnet crystals with high density ρ = 6.0 g/cm3 and Zeff = 62 can be used to evaluate the X-rays produced by the accelerator with the 15 MV beam.

Thermoluminescence kinetic parameters of yttrium niobate

Yttrium niobate (YNbO4) phosphorus produced using the solid-state technique by sintering at 1200 °C investigated for thermoluminescence (TL) kinetics after irradiated with ultraviolet radiation (UV). The TL glow curve of UV irradiated yttrium niobate phosphorus recorded with a heating rate of 2 Ks−1 exhibited glow peaks at 366 and 424 K. The TL kinetic parameters belonging to main glow peak (424 K) of yttrium niobate phosphor, namely trap energy (E), frequency factor (s) and kinetic order (b) were investigated using Various Heating Rates (VHR), Computerized Glow Curve Deconvolution (CGCD), and Chen's Peak Shape (PS) methods after exposure to UV radiation. Trap energies of the phosphor by all methods were calculated as 1.09 eV. The frequency factors of the phosphor by CGCD, VHR and Chen’s PS methods were obtained as 0.96 × 1012 s−1, 1.38 × 1012 s−1 and 0.98 × 1012 s−1, respectively. The results attained by all methods are discussed and compared.

Kinetic analysis of the main thermoluminescence glow peak in α-Al2O3

In this work the kinetic parameters of the main peak of the TL glow curve of alumina (α-Al2O3) irradiated at different doses are reported. Samples were irradiated at different X-ray doses using a 6 MeV linear accelerator (LINAC), in air at room temperature. The Initial rise, peak shape, whole glow peak and curve fitting methods were used for the kinetic analysis. The glow curves of the α-Al2O3 samples exhibited a total of three experimental glow peaks, the main peak located between 160 and 170 °C. The behavior of the kinetic parameters (activation energy E, frequency factor s and order parameter b) of the main peak of the TL glow curve, is independent of the radiation dose received by the material.

Radiation response properties of Dy-doped B2O3–Al2O3–SrO glasses

Borate glasses are considered to be host materials for thermoluminescent phosphors owing to their high thermally-stimulated luminescence (TSL) sensitivity and low effective atomic number. Herein, we fabricated the Dy-doped B2O3–Al2O3–SrO glasses to develop the phosphors for radiation dosimetry, and investigated their photoluminescence (PL), scintillation and TSL properties, systematically. The Dy-doped samples showed clear emission peaks at 480 and 570 nm due to 4f-4f transitions of Dy3+ in PL, and the 0.5 % Dy-doped sample exhibited the highest quantum efficiency of 0.24 under excitation wavelength of 350 nm among the sample tested. The decay time constants of the Dy-doped samples were 0.25–0.84 ms, which were typical values for the 4f-4f transition of Dy3+. In scintillation, the Dy-doped samples showed emissions with sharp peaks at 480 and 570 nm with the decay time constants of 0.51–0.86 ms due the 4f-4f transitions of Dy3+. The scintillation intensity of the 0.5 % Dy-doped sample was the highest among the samples investigated. Furthermore, the Dy-doped samples exhibited TSL with a main glow peak at approximately 90 °C after X-ray irradiation of 10,000 mGy, and the dynamic range of the 0.1–1.0 % Dy-doped samples was found to be 0.1–10,000 mGy.

Thermoluminescence characterization of nanocrystalline powder of SrSO4:Sm exposed to gamma radiation for dosimetric applications

Dosimetry properties of nanocrystalline SrSO4:Sm powders prepared via a co-participation method, were studied. X-ray diffraction, energy dispersive X-ray spectroscopy and Field emission scanning electron microscopy (FE-SEM) were used to investigate the structure, composition and morphology of nanocrystalline SrSO4:Sm powders. The nanocrystalline SrSO4:Sm powders had the orthorhombic crystal structure. FE-SEM image showed polygonal structure of particles with an average size of particles 0.2 μm. The thermoluminescence (TL) measurements for different concentration of samarium were done after gamma irradiation. TL glow curves showed the main glow peak at 370 °C. The maximum intensity of the TL glow curves for SrSO4:Sm was obtained with 0.05mol% concentration of Sm. Then, due to its high intensity glow curve, it was selected as the main sample. Furthermore, its dose-response, energy-response, and fading were studied in detail. Nanocrystalline SrSO4:Sm(0.05 mol%) powder had a linear dose-response approximately between 10Gy and 3 kGy. It showed energy dependence for low energy photons and its fading was less than 20% after 37 days. The X-ray excited luminescence (XEL), and TL were examined. The kinetic parameters were calculated by using the various TL analysis methods and OriginPro 8 software. The results showed the main TL glow peak obeyed second order kinetics.

Photoluminescence, scintillation and TSL properties of Tb-doped strontium aluminoborate glasses

We synthesized strontium aluminoborate glasses doped with different concentrations of Tb (0.1, 0.5, 1.0 and 5.0 mol.%) by the conventional melt-quenching technique, and investigated their photoluminescence (PL), scintillation and thermally-stimulated luminescence (TSL) properties to develop phosphor materials for radiation dosimetric methods. The Tb-doped samples showed PL and scintillation with sharp peaks approximately at 485, 540, 545, 580 and 620 nm due to the 4f-4f transitions of Tb3+. The 1.0% Tb-doped sample exhibited the highest intensity in PL and scintillation among the samples investigated. In addition, the Tb-doped samples showed TSL with a main glow peak approximately at 75 °C measured after X-ray irradiation of 1000 mGy. The TSL intensity of the 0.1% Tb-doped sample was the highest, and the 0.1–1.0% Tb-doped samples showed TSL with a linear response feature over the dose range of 0.1–1000 mGy.

Preparation, kinetic analysis and thermoluminescent dosimetry features of highly sensitive SrF2:Dy phosphor

Dy doped SrF2 microcrystalline was prepared by co-precipitation technique. Thermoluminescence (TL) glow curve of γ irradiated SrF2:Dy phosphor consists of a main glow peak at 485 K with small shoulders at around 384 K and 590 K. The effects of different dopant concentrations and annealing regimes on TL sensitivity were investigated and the optimum conditions were achieved at 1 mol% of Dy dopant and annealing at 700 °C for 30 min. Initial rise, variable heating rate, isothermal decay and computerized glow curve deconvolution (CGCD) methods were applied to obtain kinetic parameters of the prepared material. TL sensitivity of this phosphor is about 10 times more than that of LiF;Mg;Ti (TLD-100). Based on the obtained results, the synthesized phosphor is appropriate for dosimetry applications.

Thermoluminescence properties of strontium doped magnesium tetraborate

It is worth to continuous and systematic investigations related with magnesium tetraborate (MBO) due to its attractive candidate for dosimetric application. The study was done to develop new phosphor with adding strontium (Sr) into MBO which was prepared by the simple high temperature solid state method. Its main dosimetric properties, like glow curve structure, dose response, trapping parameters and fading, were investigated for the first time in the literature. The experimental results indicated that Sr doped MBO ensured essential characteristics for applicability in medical dosimetry, except for the fading (45% lost in 7 days) feature. It had main glow peak with highest intensity at nearly 200 °C with good linearity of the dose–response up to 1150 Gy. This study suggests that Sr-doped MBO is a promising material for dosimetric application, just need to solve the fading problem with addition of another activators as a co-dopant.

General features and kinetic analysis of thermoluminescence from annealed natural quartz

The aim of this study is to explore the thermoluminescence properties of beta irradiated natural quartz annealed at 900 °C, that is, beyond its second phase inversion temperature of 867 °C. The sample was annealed to improve its sensitivity and to deplete any residual charge from electron traps. The glow-curve corresponding to 10 Gy shows three peaks when measured at 1 °C/s; a dominant one at 71 °C, the subject of this report, and two other ones at 125 and 177 °C. The dose response of the main peak was studied in the range 1–300 Gy. The activation energy of the main glow-peak was evaluated as ~1 eV. Kinetic analyses using various methods show that the main glow-peak follows first order kinetics.

Thermoluminescence of the persistent-luminescence phosphor, BaAl2O4; A stuffed tridymite

BaAl2O4 is a stuffed tridymite used as a long-lasting phosphor. The thermoluminescence of BaAl2O4 prepared by solution-combustion is reported. Analysis of the sample using X-ray diffraction shows that it formed as a single phase compound with a hexagonal structure following annealing at 1200 °C. A broad photoluminescence emission band between 300 and 650 nm was detected due to excitation at 248 nm. The phosphor showed a natural TL peak at 102 °C for measurement at 1 oCs−1 and, when beta irradiated to 100 Gy, two broad peaks at 123 and 318 °C also for heating at 1 oCs−1. The analysis of the main glow peak at 123 °C suggests that it is a combination of several collocated peaks, that is, peaks embedded within each other. We resolved four such components labelled peaks 1 to 4. The thermoluminescence decreases with heating rate in a way consistent with thermal quenching whose activation energy was determined as ∼0.65eV using peak 3. Interestingly, this value of the activation energy for thermal quenching for BaAl2O4, a stuffed derivative of silica, is similar to literature values for quartz (a silica), suggesting that the recombination centre in the two cases may be similar.

Photoluminescence and Thermoluminescence Properties of Sol-Gel Auto-Combustion Driven Mg2SnO4 Nanophosphor

Nanocrystalline Mg2SnO4 nanophosphor was synthesized by a facile sol-gel auto-combustion method calcined 800°C for 1 h. The X-ray diffraction pattern showed that the nanopowder has a cubic inverse spinel polycrystalline structure with an average crystallite size of about 20 nm. The photoluminescence spectra were measured at 84−300 K, and the broad emission band was obtained in the wavelength range of 400−500 nm. Photoluminescence at 120 K showed the highest emission band centered around 414 nm. The thermoluminescence (TL) glow curve showed an increase in TL peak intensity with UV irradiation time due to the increasing number of inherent traps created by UV irradiation. The maximum TL intensity was found for 30 min UV exposure. Activation energies of the trapping centers were found between 0.39 eV and 0.48 eV. The frequency factor of the main glow-peak was also evaluated in the 3.03 × 106–4.26 × 107 s−1 range for UV irradiated phosphor. The decrease in activation energy and frequency factor with increasing UV exposure time may attribute to the decrease in trap depth. The calculated trap parameters related to the glow peak show this phosphor may be useful in radiation dosimetry applications.

Radio-Optically- and Thermally Stimulated Luminescence of Zn(BO2)2:Tb3+ exposed to Ionizing Radiation

The optical absorption of zinc tetraborate at different concentrations of the terbium impurity (0, 0.5, 1, 2, 4, 8 mol%) was analyzed. The radioluminescence (RL) emission spectra was obtained after beta irradiation of a 90Sr/90Y source. The RL spectrum showed the characteristics bands of Tb3+ with two main emissions at 489 nm and 546 nm which corresponding to the5D4→7F6 and 5D4→7F5 transitions respectively in this ion. The OSL and TL characteristics have been analyzed. The stimulation blue light (497 nm) of a diode laser at 500 mA was used to bleach the thermoluminescent (TL) signals obtained with 5Gy of 60Co source. The two main glow peaks (79 and 161 °C) are sensitives under 497 nm stimulation, and they were shifted to higher temperature values and faded their TL intensities. Similar behavior of TL glow curves before and after OSL stimulation with blue light was observed when the samples were exposed to 30 Gy gamma dose of 137Cs irradiator. The OSL signal response was linear with the dose range of 1-10 Gy and increased their response up to 200 Gy gamma dose. The OSL shows a bleaching sensitive shallow traps and diminishing the intensity of the TL glow curves remaining a complex traps distribution. The RL, TL and OSL properties were investigated in Zn(BO2)2:Tb3+ phosphor.

The influence of dose on the kinetic parameters and dosimetric features of the main thermoluminescence glow peak in α-Al2O3:C,Mg

The influence of dose (0.1–100Gy) on the kinetic parameters and the dosimetric features of the main glow peak of α-Al2O3:C,Mg have been investigated. Thermoluminescence (TL) measured at 1°C/s shows a very high intensity glow peak at 161°C and six secondary peaks at 42, 72, 193, 279, 330, 370°C respectively. Analysis shows that the main peak follows first order kinetics irrespective of the irradiation dose. The activation energy is found to be consistent at 1.37eV and the frequency factor is of the order of 1014s−1 for any dose between 0.1 and 100Gy. Further, the analysis for thermal quenching of the main peak of 0.1Gy irradiated sample shows that the activation energy for thermal quenching is (0.94±0.04) eV.Regarding the dosimetric features of α-Al2O3:C,Mg, the dose response of the main peak is superlinear within 0.1 to 30Gy of beta dose and then it becomes sublinear up to 100Gy. Fading analysis shows that the intensity of the main peak drops to ∼22% of its initial value within 2400s after irradiation and thereafter to ∼14% within 64,800s. Analysis of the reproducibility shows that the coefficient of variation in the results for 10 identical TL measurements show that reproducibility improves with increase in dose.

Thermoluminescence of α-Al2O3:C,Mg: Kinetic analysis of the main glow peak

The kinetic analysis of the thermoluminescence of aluminium oxide doped with carbon and co-doped with magnesium (α-Al2O3:C,Mg) is reported. Measurements were made at 1°C/s following beta irradiation to 1Gy. The glow curve consists of a dominant peak at a peak-maximum Tm of 161°C and six secondary peaks of weaker intensity at 42, 72, 193, 279, 330 and 370°C. Kinetic analysis of the main peak, the subject of this report, was carried out using initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the main peak was determined as first order using various methods including the Tm–Tstop technique and the dependence of Tm on irradiation dose. The activation energy of the peak is about ~1.36eV and the frequency factor of the order of 1014s−1. The peak area changes with heating rate in a manner that shows that the peak is affected by thermal quenching. The activation energy of thermal quenching was evaluated as 0.99±0.08eV. A comparison of analytical results from the main peak before and after correction for thermal quenching show that the kinetic parameters of the main peak are not that affected by thermal quenching.

Influence of SrF2-doping in AlN ceramics on scintillation and dosimeter properties

In this study, we synthesized undoped AlN and SrF2-doped AlN (AlN-SrF2) ceramics by Spark Plasma Sintering (SPS), and we characterized their optical, scintillation and dosimeter properties. The prepared undoped AlN ceramic had gray color and visually non-transparent whereas, with an addition of SrF2, the transparency improved and became translucent. The measured in-line transmittance was approximately 0.2% at wavelengths longer than 500 nm. While the addition of SrF2 decreased the scintillation intensity, the decay time was significantly fastened, which is a great advantage for fast photon counting-based measurements. Both the thermally-stimulated luminescence (TSL) and optically-stimulated luminescence (OSL) showed good linear response from the milli-gray range to over 10 Gy. The sensitivity seems to decrease by an addition of SrF2 as it suppresses structural defect centers which are responsible for dosimeter properties. However, the main TSL glow peak position shifts to higher temperature with the addition of SrF2, which indicates that inclusion of SrF2 improves the TSL signal stability.

Gamma induced thermoluminescence and color centers study of Dy doped LiF micro-cubes

In this paper, we present the thermoluminescence and optical absorption studies of Dy-doped LiF phosphors. The phosphors were synthesized via co-precipitation method, in which the reactions were carried out at fixed pH value 8.00. X-ray diffraction (XRD) patterns revealed single phase structure of phosphors up to concentration (0.04mol%) of Dy in the host lattice of LiF. The field emission scanning electron microscope (FE-SEM) images showed micro-cubical morphologies. The incorporation of Dy in LiF was confirmed from the results of electron dispersive spectroscopy (EDS) and XRD. The thermoluminescence (TL) glow curves of γ-irradiated samples in the dose range (0.1–50kGy) revealed a main dosimetric glow peak positioned at 417K. Moreover, at irradiation dose of 10kGy and above, a broad TL band towards higher temperature side of main dosimetric peak also appeared. Using TLanal program, the complex TL glow curves were deconvoluted and TL kinetics parameters namely; the activation energies, frequency factors and order of kinetics were evaluated. The results revealed the formation of additional localized trapping sites of different values of activation energy and frequency factor in the forbidden band. The optical absorption study revealed the formation of radiation induced stable color centers (CCs) at room temperature. The concentrations of CCs were evaluated using Smakula's formula.

Thermoluminescence Study of Gamma Irradiated Cr-Doped LiF Phosphors

We have synthesized Cr-doped LiF phosphors by using modified co-precipitation. X-ray diffraction study confirms the single-phase cubic structure up to 0.05 mol.% of Cr in LiF; afterwards, a secondary phase of formation was observed. The field emission scanning electron microscope (FESEM) images revealed micro-cubic surface morphology of samples. The thermoluminescent (TL) behavior of the samples studied after irradiating them with gamma rays in the dose range 0.1–30 kGy. The TL glow curve of Cr-doped LiF comprises a prominent peak observed at 407 K and a broad band ranging from 448 K to 512 K at a fixed gamma dose of 10 kGy. The shape of the TL glow curve remained similar at all concentrations of Cr in LiF; however, TL intensity was found to vary with Cr concentration, and Cr (0.02 mol.%)-doped LiF sample exhibit highest TL response. The glow curve of the optimized sample as a function of gamma irradiation dose within the range 0.1–30 kGy shows an almost linear increase in TL intensity of the main glow peak up to 10 kGy, and afterwards it decreases. Further, at the high dose of 30 kGy, the intensity of the prominent TL glow peak at 407 K decreases and another broad peak starts growing at 468 K signifying the formation of new trapping sites. The kinetic parameters, namely activation energy, order of kinetics, and frequency factor of the optimized sample were evaluated by using Chen’s peak shape method and glow curve deconvolution (GCD) functions based on Kitti's equations.