Complex Thermoluminescence Glow Curves Research Articles

Structural, thermoluminescence and optical properties of Nd3+ doped Y2O3 nanophosphor for dosimeter and optoelectronics applications

For potential gamma ray dosimetry and near-infrared laser material applications, solution combustion synthesis was used to create undoped and trivalent neodymium doped Y2O3. X-ray powder diffraction was used to analyze the annealed materials. It was discovered that they had a cubic Y2O3 single phase structure up to a dopant level of 2 mol%. The higher dopant concentrations showed the existence of a Nd2O3 solid solution. The crystallite sizes were determined using Scherrer and Williamson-Hall equations and were found to decrease with dopant content. Characterization of the nanocrystals by X-ray photoelectron spectroscopy confirmed excellent stoichiometric control. The γ-ray irradiated phosphors showed a thermoluminescence (TL) peak at about 394 K that sub linearly increased in intensity up to 7 kGy and thereafter decreased. A computerized glow curve deconvolution algorithm was used to analyze the measured complex TL glow curves produced for the phosphors exposed to γ-rays. The 60Co γ-ray irradiated Nd3+ doped Y2O3 sample exhibited peaks at 395, 445, 496 and 596 K with the corresponding activation energies in the range of 1.20-1.32 eV. These were attributed to the F, F+ and V-centers. The main absorption bands, i.e., at 590 and 812 nm for the Nd:Y2O3 nanocrystals. As the host's Nd3+ content increased, the optical band gap decreased. Three major emission bands at wavelengths of 871–957, 1045–1137, and 1306–1379 nm were associated with Nd3+ transitions of 4F3/2→4I9/3, 4F3/2→4I11/3 and 4F3/2→4I13/3, According to calculations, the 4F3/2 energy level's PL lifespan for Nd3+ doped Y2O3was between 68 and 247 µs.

Thermoluminescence response to identification of Mexican Ancho and Chipotle chilli irradiated with 137Cs gamma photons

In this work, the thermoluminescence (TL) properties of mineral content in Mexican Ancho and Chipotle chilli were studied for their application in the detection of irradiated chilli. The Ancho and Chipotle chilli minerals show a complex TL glow curve with two overlapping peaks around 82 and 178 °C. Acceptable repeatability of TL measurements is obtained after ten irradiation-readout cycles. The dose-response of Ancho and Chipotle minerals is linear from 5 to 75 Gy, supralinear between 100 and 1000 Gy, and sublinear from 1500 to 5000 Gy. Using the TL1/TL2 ratio, the chilli minerals are detected as irradiated at doses ≥200 Gy. At low doses (<200 Gy) the TL glow curve shape, intensity, and temperature maximum position parameters are used for identifying irradiated chilli minerals. At 360 min of sunlight exposure, the TL intensity of Ancho and Chipotle chilli minerals decreased by 95 and 98%, respectively. On the contrary, the chilli minerals stored at room temperature, in the darkness, can be detected by TL as irradiated after 960 h (40 days) post-irradiation. The TL kinetic parameters were evaluated by the computerized glow curve deconvolution (CGCD) analysis.

Determination of Thermoluminescence Kinetic Parameters of La2O3 Doped with Dy3+ and Eu3.

Thermoluminescence (TL) properties of La2O3: Dy3+, Li+, and La2O3: Eu3+, Li+, exposed to 5.12 Gy of beta radiation, and recorded at different heating rates 0.5, 1, 2, 3, 4, and 5 °C s−1 (from Molefe et al., paper 2019), were analyzed and the trap parameters were determined in this study. These parameters include the order of kinetics b, the activation energy E (eV), the frequency factor S (s−1), or the pre-exponential factor S″ (s−1), and the initial concentration of trapped electrons no (cm−3). A new non-linear curve fitting technique, based on the general order kinetic equation and the outcomes of Hoogenstraaten’s Method, was established and applied on the TL glow peaks of La2O3: Dy3+, Li+. The fitting technique was evaluated by calculating the R-square and figure of merit (FOM) values. The results revealed that the FOM values are <1%, and the R-square values are >0.997, which demonstrates an excellent convergence between experimental and fitted curves. A modified technique based on the three-points analysis method was exploited to deconvolute complex TL glow curves of La2O3: Eu3+, Li+, and in turn, to determine the trap parameters the method disclosed that each TL glow curve consists of four peaks. The trap parameters of the individual peaks were numerically determined. The fading, as a function of storage temperature and time, from the TL signals of the investigated materials was predicted and discussed based on the calculated trap parameters. The results support the value of the materials for employment in radiation dosimeter applications with a low fading fraction.

On the resolution of overlapping peaks in complex thermoluminescence glow curves

Experimental Thermoluminescence (TL) glow curves for most dosimetric materials are composites, consisting of weakly or strongly overlapping peaks. The ability to discriminate between two overlapping peaks defines the resolution of a TL glow curve. Although the concept of resolution has been defined and used widely in many areas of science, there have been no previous attempts to define and study the resolution of overlapping TL peaks. In this work the resolution parameter R is defined in terms of the geometrical characteristics of TL peaks. A large number of TL glow curves consisting of two peaks were numerically evaluated for various degrees of overlapping between them. These numerically generated glow curves were analyzed by a computerized glow curve deconvolution analysis, in order to determine the reliability of the deconvolution results as a function of the resolution parameter R.

Analysis of Thermoluminescence Glow Curves using Derivatives of different Orders.

The suitability of the second derivative method for locating component peaks in complex thermoluminescence (TL) glow curves has been investigated in this work by considering both numerically simulated and experimental TL peaks. This technique is useful to acquire knowledge of the number of component peaks in a complex TL curve which in turn serves as a basic information before applying the deconvolution technique to the glow curve. To check the consistency of the results so obtained, we have also applied the first derivative technique to TL glow curves. It is well-known that kinetic order formalism fails for saturated TL peaks with heavy retrapping. Such peaks are usually broad and, to the best of our knowledge, have not yet been observed experimentally. The present derivative technique has been used to detect whether such broad peaks are truly single or not by considering a number of numerically simulated saturated glow curves with heavy retrapping where the conventional peak shape method fails. In all the cases considered here, the second derivative technique proves to be a potential candidate for estimating the number of peaks and their respective locations in a complex TL glow curve.

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 sensitivity of ulexite after UV irradiation

The effects of UV radiation on the thermoluminescence (TL) properties of natural materials, in contrast to synthetic materials, have been scarcely studied. We report on the UV-induced thermoluminescence emission of a Turkish ulexite (NaCaB5O6(OH)6·5H2O) that displays very complex TL glow curves, with at least three groups of components peaked at 130–140°C, 240°C and, 340°C, wherein the last group is weaker. Such emission could be associated with structural changes in the lattice as well as alkali self-diffusion processes. The UV exposure performed at controlled temperatures (at room temperature (RT), 50°C and 100°C) produced a (i) different evolutions of the intensities of each maximum, which are directly related to the controlled thermal treatment; (ii) different intensity ratios among the groups of components; (iii) different activation energies (Ea) (1.13eV for RT, 0.99eV for 50°C and 0.49eV for 100°C) calculated using the initial rise method; and (iv) similar scattering values (12.4%, 8.2% and 12.8%), which were not a function of the controlled temperature. The thermal stability tests conducted on this borate at different temperatures, based on the Tstop protocol, confirm the presence of a continuum in the distribution of the trap system with progressively increasing Ea (from 0.60 to 0.90eV).

Understanding Persistent Luminescence: Rare-Earth- and Eu2+-doped Sr2MgSi2O7

Similar to many other Eu2+,RE3+-co-doped persistent luminescence materials, for Sr2MgSi2O7:Eu2+,RE3+ the initial intensity and duration of persistent luminescence was also found to depend critically on the rare-earth (RE) co-doping. An enhancement of 1 - 2 orders of magnitude in these properties could be obtained by Dy3+ co-doping whereas total quenching of persistent luminescence resulted from the use of Sm3+ and Yb3+. To solve this drastic disparity, the effects of the individual RE3+ ions were studied with thermoluminescence (TL) spectroscopy to derive information about the formation of traps storing the excitation energy. The charge compensation defects were concluded to be the origin of the complex TL glow curve structure. The tuning of the band gap of the Sr2MgSi2O7 host and especially the position of the bottom of the conduction band due to the Eu2+,RE3+ co-doping was measured with the synchrotron radiation vacuum UV (VUV) excitation spectra of the Eu2+ dopant. The model based on the evolution of the band gap energy with RE3+ co-doping was found to explain the intensity and duration of the persistent luminescence.

Synthesis and luminescence properties of Ce3+ doped MWO4 (M=Ca, Sr and Ba) microcrystalline phosphors

The Ce3+ doped and undoped samples of alkali earth metal tungstate MWO4 (M=Ca, Sr, and Ba) phosphors are synthesized by a co-precipitation method in controlled pH environment. The resulting phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), photoluminescence (PL) and thermoluminescence (TL). XRD pattern and SEM micrographs reveal the formation of agglomerated microcrystalline phosphor. FTIR spectra show the strong absorption around 821cm−1 due to characteristic vibrations of (WO4)2− complex. PL excitation spectra show broadband in the UV region having peak at 280nm, and the emission spectrum shows broadband in the visible region with peak in the blue region. The PL emission intensity increases with Ce3+ concentration with the most effective concentration at 5mol%. The complex TL glow curve of Ce3+ doped phosphors is deconvoluted by using a TLAnal computer program. The trap parameters obtained by TLAnal were compared with those calculated by Chen׳s method and a possible model for TL is discussed.

Identification of gamma-irradiated ingredients in liquid seasonings by thermoluminescence analysis: an interlaboratory blind trial

An interlaboratory blind trial was conducted to validate the thermoluminescence (TL)-based identification of gamma-irradiated (0, 1, and 10 kGy) ingredients (garlic powder) in liquid seasonings. Two kinds of forty (20 each) coded samples containing irradiated ingredients at blending ratio of 0–3 % were processed in a food industry and sent to two different irradiation detection laboratories. The garlic powders were also analyzed by both laboratories as reference materials. Irradiated garlic powder provided a strong TL peak at about 200 °C, which was absent in the non-irradiated ones, and the results were also confirmed by determining the TL ratio (TL1/TL2). In the blind trial of sauces containing an irradiated ingredient, 75–80 % validated results were reported. The problematic results were observed for the samples containing low quantities of 1 kGy-irradiated ingredients. The TL ratios of all sauce samples were <0.1 irrespective of their irradiation history, where the evaluation was made using the glow curve shapes and intensities. Low amounts of irradiated ingredients could be effectively detected; however, the lower detection limits need to be established after getting a better understanding of the complex TL glow curve results.

물리적 확인시험법을 이용한 시판 유통 중인 고춧가루의 방사선 조사여부 판별 모니터링

Ten commercially available red pepper powders were investigated using photostimulated-luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR) analyses to confirm their irradiation status. The application of PSL, TL, and ESR analyses was also confirmed by in-house irradiation. In PSL-based screening, all samples gave negative photon counts (<700 PCs). The PSL calibration dose (1 kGy) showed a low sensitivity of 4 samples, while the others provided reliable screening results. TL glow curves demonstrated maximum peaks after 250 o C for the 6 samples; however 4 samples gave complex TL glow curves with maximum peaks in the range of 185-260 o C (radiation-specific), which could be the effect of an irradiated component in low concentration as the TL ratios of all samples were <0.1. Radiation-specific ESR features were absent in the all commercial samples. Variable irradiation detection properties were found; where the TL analysis showed the possible presence of an irradiated component in 4 samples requiring further monitoring and investigation.

Thermoluminescence studies of CaS : Bi nanocrystalline phosphors

The thermoluminescence (TL) studies of CaS : Bi nanocrystalline phosphors prepared by the wet chemical co-precipitation method and exposed to γ-rays have been discussed. The average grain size of the samples was estimated as 35 nm using Scherrer's equation. The samples exhibit a complex TL glow curve with multiple peaks. Sample exposed to γ-rays showed that the TL intensity increases linearly as the radiation doses increased in the 1.012–40.48 mGy range. The trap parameters namely, activation energy (E), order of kinetics (b) and frequency factor (s) of the main peaks of the CaS : Bi(0.08 mole%) sample have been determined using Chen's method. The effect of different dopant concentrations and different heating rates has also been discussed.

GlowFit—a new tool for thermoluminescence glow-curve deconvolution

A new computer program, GlowFit, for deconvoluting first-order kinetics thermoluminescence (TL) glow-curves has been developed. A non-linear function describing a single glow-peak is fitted to experimental points using the least squares Levenberg–Marquardt method. The main advantage of GlowFit is the ability to resolve complex TL glow-curves consisting of strongly overlapping peaks, as those observed in heavily-doped LiF:Mg,Ti (MTT) detectors. This resolution is achieved mainly by setting constraints or by fixing selected parameters. The initial values of the fitted parameters are placed in the so-called pattern files. GlowFit is a Microsoft Windows-operated user-friendly program. The graphic interface enables easy intuitive manipulation of glow-peaks, at the initial stage (parameter initialization) and at the final stage (manual adjustment) of fitting peak parameters to the glow-curves. The program is freely downloadable from the web site http://www.ifj.edu.pl/dept/no5/nz58/deconvolution.htm

Afterglow thermoluminescence band as a possible early indicator of changes in the photosynthetic electron transport in leaves

The afterglow (AG) band of thermoluminescence (TL) has been investigated in leaves of Arabidopsis thaliana. Excitation of dark-adapted leaves with two saturating single turn-over flashes induced the appearance of a complex TL glow curve that could be well simulated by three components: the two components, B1 and B2, of the usually called B-band, peaking at 18 and 26 degrees C, respectively, and a band with tmax at 41 degrees C, which we attributed to an AG emission. Illumination of dark-adapted leaves with 720 nm monochromatic and FR lights generated the emission of a sharp single band peaking also around at 41 degrees C, that it is usually assigned to an AG emission band. Dark-incubation of whole plants increased the intensity of AG-band in TL curves induced by two flashes and, in parallel, decreased B-bands. Selective illumination of leaves with light mostly absorbed by PS II (650 nm light) completely abolished the AG-band induced by two flashes, B-band being the only TL band observed. The single AG-band induced by 720 nm light was abolished if leaves were also illuminated with 650 nm light. On the other hand, AG-band could be restored if 650 nm illuminated leaves were afterwards illuminated with 720 nm light. The changes in the intensity of B and AG bands induced by selective illuminations seem to be related to alterations in the redox state of QB and plastoquinone pool.

A thermoluminescence study of Photosystem II back electron transfer reactions in rice leaves – effects of salt stress

The recombination reactions of Photosystem II have been investigated in vivo in rice leaves by using the thermoluminescence (TL) emission technique. Excitation of dark-adapted leaf segments at 0 degrees C with different number of single turn-over flashes induced the appearance of complex TL glow curves. The mathematical analysis of these curves showed the existence of four TL components: B1-band (temperature maximum, t(max), at 24 degrees C, originating from S3QB - recombination), B2-band (tmax at 35 degrees C, from S2QB -), AG-band (tmax at 46 degrees C) and C-band (tmax at 55 degrees C, from TyrD +QA -). Their contributions to the total TL signal were different depending on the number of flashes given. AG-band seems to reflect a special electron transfer from some unknown stroma donor to PS II. Q-band (tmax at 19 degrees C), originating from S2QA - recombination, was recorded after flashing samples incubated in the presence of DCMU. The recombination halftimes (t1/2) at 20 degrees C of S2QA -, S3QB -, S2QB - and TyrD +QA - were, respectively, 0.8 s, 48 s, 74 s and about 1 h. A sharp AG-band (tmax at 50 degrees C and t1/2 of 210 s) could be also observed after illumination of leaves with far-red light and after a dark incubation period of whole plants. Incubation of leaf segments with 0.5 M NaCl abolished the inductions of AG-band by darkness and far-red illumination, significantly decreased Q-band intensity, whereas induced a strong increase in C-band intensity. The possible inhibition of S2/S3 formation and quinone oxidation by saline stress are discussed.

Fit of first order thermoluminescence glow peaks using the Weibull distribution function.

A new thermoluminescence glow curve deconvolution (GCD) function is introduced which accurately describes first order thermoluminescence (TL) curves. The new GCD function is found to be accurate for first order TL peaks with a wide variety of the values of the TL kinetic parameters E and s. The 3-parameter Weibull probability function is used with the function variables being the maximum peak intensity (Im), the temperature of the maximum peak intensity (Tm) and the Weibull width parameter b. An analytical expression is derived from which the activation energy E can be calculated as a function of Tm and the Weibull width parameter b. The accuracy of the Weibull fit was tested using the ten reference glow curves of the GLOCANIN intercomparison program and the Weibull distribution was found to be highly effective in describing both single and complex TL glow curves. The goodness of fit of the Weibull function is described by the Figure of Merit (FOM) which is found to be of comparable accuracy to the best FOM values of the GLOCANIN program. The FOM values are also comparable to the FOM values obtained using the recently published GCD functions of Kitis et al. It is found that the TL kinetic analysis of complex first-order TL glow curves can be performed with high accuracy and speed by using commercially available software packages.

On the analysis of complex thermoluminescence glow curves

On the analysis of complex thermoluminescence glow curves

Charge trapping mechanisms and microdosimetric processes in lithium fluoride

We present a review of the charge trapping and recombination mechanisms in LiF thermoluminescence (TL) dosimeters and discuss several dosimetric properties of this material in the light of these processes. The complex TL glow-curve from LiF doped with Mg, Ti and OH impurities consists of several individual peaks which emit in the region of 420–460 nm, depending on the glow peak temperature. The kinetics of the process appear to be first-order. From an accumulation of experimental data from a variety of sources (dielectric loss, ionic thermocurrents, ionic conductivity, photoluminescence, X-ray-induced luminescence, optical absorption, electron spin resonance, and others) it is inferred that the TL emission near 200°C is the result of electron-hole recombination at defect complexes consisting of Mg trimers and TiOH n centers. The spatial localization of the Mg defects and the Ti defects is seen to be of fundamental importance in describing certain aspects of the dose response function of this material and the stability of the TL signal. Coupled with this, however, the microscopic processes of energy deposition, in which regions of high ionization density are formed inside the irradiated sample, are seen to provide the essential framework around which it is possible to establish a model to describe all the major features of the dose response function in LiF:Mg, Ti, OH for a variety of irradiation types.

A fast method for the evaluation of complex thermoluminescence glow curves

The paper describes a simple and fast computer method for the evaluation of multipeak TL glow curves. Preliminary experimental results indicate, that due to its fastness and reliability the method can be applied in routine personnel monitoring and even some of the time consuming annealing precesses of the TL detectors can be eliminated. Other possible areas of application are also reviewed.