Temperature Thermoluminescence Research Articles

Unusual heating rates, dose responses and kinetic parameters detected on thermoluminescence from YAl3(BO3)4:Sm3+ phosphors

This study focused on the thermoluminescence (TL) characteristics of YAl3(BO3)4 (YAB) phosphors modified with various contents of Sm3+ ions. The TL response of the YAB: Sm3+ phosphors exposed to beta irradiation was measured across the temperature range of 25–500 °C, exhibiting three TL maxima at 70, 235, and 408 °C. Preheating protocol was also carried out to remove the low temperature TL peak followed by further experiments with the two-remaining high-temperature peaks. In the TL measurements conducted with variable heating rates (HR) between 0.1 and 5 °Cs-1, an anomalous heating rate behaviour was observed. A semi-localized transition model was used to address this feature. There was a standard deviation of less than 5% in the reusability measurements. The results of the kinetic parameters obtained by initial rise (IR) and various heating rate (VHR) methods were compared with those obtained by glow curve deconvolution (GCD) method. Tm-Tstop analysis revealed a continuous distribution of trap levels with a trap depth ranging from 1.35 to 2.20 eV. Through the use of GCD, the glow curve was found to demonstrate general order kinetics and consist of seven superimposed traps. The values of the kinetic parameters obtained for the glow curve agreed with those obtained by other methods excluding the VHR method encountering an anomalous impact. The results obtained from these tests showed that the sample could be successfully used for TL dosimetry applications.

Low temperature luminescence and tunnelling effect in the Sr4Al14O25 co-doped with Eu2+and Dy3+ persistent luminescent phosphor

Thermoluminescence (TL) technique is very useful in the research of persistent Luminescence (PL) phosphors. It gives information about the existence of energy levels within the forbidden band and lifetime. The TL glow curve of Sr4Al14O25: Eu2+,Dy3+ persistent phosphor consists of two well-separated glow peaks at around 353 K and 438 K after both UV radiation and beta irradiation. To study the low temperature (≤ room temperature) glow peaks, low temperature TL (LTTL) measurements were performed with a homemade system after exposed to UV radiation. The sample was heated according to T(t)=T∞−(T∞−T0)e−αt equation starting from liquid nitrogen temperature, 77K. Besides the peaks at around 345 and 445 K according to LTTL results, Sr4Al14O25: Eu2+,Dy3+ has two more well-separated low temperature TL peaks at around 170 K and 295 K.The lifetime of the TL glow peaks (at 353 K and 438 K) was calculated according to s−1exp(EkT) and the results were checked with fading tests. Moreover, TL sensitivity tests were carried out both with and without preheating. Finally, tunnelling effect was evaluated by using the results of sensitivity tests and fading tests. Interesting results were observed at sensitivity tests performed with preheating. The results indicates that the behaviour of two glow peaks is very different from each other. The mechanism behind the peak around 438 K is localised transition involving a tunnelling effect.

TL and EPR characteristics of SrAl2O4 phosphor prepared by solid‐state reaction method

SrAl2O4 phosphor was prepared by solid-state reaction method and characterized using X-ray diffraction (XRD), thermoluminescence (TL) and electron paramagnetic resonance (EPR) spectroscopy. TL glow curve of irradiated phosphor shows three peaks at 135, 260 and 350 °C. The order of kinetics of the three TL peaks is second order with an activation energy of 1.05, 1.60 and 1.93 eV, respectively. EPR studies have been carried out to identify the defect centers induced by gamma irradiation and also to identify the defect centers involved in the TL process in SrAl2O4. Two distinct centers contribute to the observed spectrum at room temperature. Center I exhibiting a four-line hyperfine splitting is identified as an O− ion. O− ion is associated with the high temperature TL peaks at 260 and 350 °C. An eight-line spectrum with a g-value of 2.0068 is attributed to a F+ center (singly ionized oxygen vacancy). This center relates to the 135 °C TL peak.

Trap level spectroscopy of disordered materials using thermoluminescence: An application to aluminosilicate glass

A method is presented for analyzing complex thermoluminescence (TL) glow curves from disordered materials using aluminosilicate glass as an example. The method is first described using simulated TL glow curves, firstly by assuming a Gaussian distribution of trap depths Et and a fixed frequency factor s, and secondly by assuming distributions of both Et and s. The method is able to reproduce the input distributions for both Et and s with a high degree of accuracy. The method is then applied to the measured TL from an aluminosilicate glass sample. A series of glow curves is recorded at different heating rates and the method is first applied to each glow curve separately, and Et and s distributions are obtained; four different trapping sites are revealed within the material, each with distributions in Et and s. Good self-consistency is obtained at each of the different heating rates. The lowest temperature TL peak shows signs of fading at the lowest heating rates used. The method is then applied to a “pseudo” TL curve consisting of the sum of all individual glow curves obtained at the different heating rates as a simple way to fit all curves recorded at the different heating rates simultaneously. The results obtained are consistent with those obtained by fitting the glow curves individually.

Luminescence Characteristics of Intraplate-Derived Olivines

Abstract Olivine has so far attracted limited attention as a potential luminescence dosimeter. In particular, there is a dearth of information concerning the luminescence properties of geochemically characterised, pure olivine samples. Six well-characterised olivine samples from four intraplate settings are investigated in this study, including emission wavelengths and intensities, growth of signal with absorbed dose, signal stability and recovery of a given dose with a single aliquot regeneration (SAR) protocol. All tested olivines share a low-temperature (90–100°C) UV/blue thermoluminescence (TL) peak, and five of six samples also produce a low-temperature red/yellow emission. Higher temperature TL peaks, which would be thermally stable over geological timescales and could be used for dating, are rarely observed at low doses (c. 46 Gy), but detectable though dim at significantly higher doses (c. 460 Gy). Photostimulated luminescence (PSL) emissions are very dim, but reliably detected emissions are stimulated by blue, yellow and infrared (IR) light. PSL yielded generally successful dose recovery results; however, all tested signals are prone to significant anomalous fading and complex thermal transfer between unbleachable and bleachable traps. These characteristics must be addressed if olivine is to be used as a natural dosimeter for luminescence dating. Given the variety of luminescence responses, it appears that olivine samples in future dating work may need to be individually characterised prior to measurement.

RELIABILITY OF REUSING THE SENSITIZED LIF THERMOLUMINESCENCE DOSIMETERS

The reliability of reusing the sensitized thermoluminescence (TL) for LiF (TLD-100) dosimeters have been investigated. It has been found that reusing the same sensitized LiF dosimeters may influence the sensitivity of the dosimeters even under the same experimental conditions when the temperature readout range does not include the high-temperature TL signal at T > 505K. But, if the high-temperature TL signal is included in the temperature readout range, it has been found that the ultra-high temperature TL signal significantly increases with increasing the number of reusing the dosimeters. After almost 7 times of reusing the sensitized dosimeters, the total area under the glow-curve becomes stable and independent of the number of reusing the dosimeters. It has been also found that the TL signal located between the low-temperature TL signal and the ultra-hightemperature TL signal was almost stable over all the number of reusing the dosimeters. For all the lowtemperature peaks, the kinetics parameters of the sensitized LiF dosimeters have not to be influenced by reusing the same dosimeters. However, the activation energy of peak 5 which lies at temperature range (460-500K) has been influenced by the readout temperature range and reusing the dosimeters. The typical value for this glowpeak has been obtained in the case which the high-temperature TL signal has been included in the temperature readout.

A component resolved study on the stable signal of Merck α-quartz: Tentative correlation among TL peaks, OSL components and EPR signals

In the present work, pre-dosed α-quartz is investigated towards its effective applications in retrospective dosimetry and dating as a reference material. The purpose of the study is to find tentative correlations between Thermoluminescence (TL) (high temperature TL (HTTL) peaks), Optically Stimulated Luminescence (OSL) (both continuous wave (CW) and linear modulated (LM)) and Electron Paramagnetic Resonance (EPR). The present work indicates a triple correlation between the fast CW-OSL component and certain peaks of LM-OSL and TL signals, while all these luminescence entities are attributed to the EPR signal with g-value (Landé splitting factor) at 1.9975 called C2EPR. The present study provides experimental evidence that (i) one TL peak might be the source for more than two LM-OSL components and (ii) even two different TL peaks can contribute to the same OSL component. Furthermore, on the EPR signal, besides the well established Ge center, another un-identified component has been resolved.

Thermoluminescence and infrared stimulated luminescence in long persistent monoclinic SrAl2O4:Eu2+,Dy3+ and SrAl2O4:Eu2+,Nd3+ phosphors

We report on the photoluminescence, long persistence luminescence, and thermally and optically stimulated luminescence properties of SrAl2O4:Eu2+,Dy3+ and SrAl2O4:Eu2+,Nd3+ phosphors synthetized by the combustion method and annealed under a carbon atmosphere at 1150 °C for 6 h. XRD indicated the presence of a single monoclinic crystalline phase for both phosphors. After exposure to beta radiation, the phosphors exhibited an intense persistent luminescence lasting more than 220 h. After excitation with 375 nm light the emission spectra depict a broad band peaked at 515 nm, which is the characteristic for Eu2+ emission in SrAl2O4 phosphors, and two weak bands at about 405 and 425 nm. After beta irradiation, the Dy co-doped phosphor exhibits an intense thermoluminescence (TL) with a maximum around 60 °C and a weaker peak at 140 °C. The low temperature TL of the Nd co-doped phosphor consist of three peaks; two well-separated peaks with maxima at about 80 and 160 °C and the third one with the maximum near 50 °C, which becomes evident at doses higher than 10 Gy. Stimulation with IR light of 830 nm releases trapped charges caused by irradiation exposure, generating an intense IR stimulated luminescence (IRSL), which exhibits a typical time decay behavior for continuous wave optically stimulated luminescence. The persistence luminescence and IRSL were related to the release of electrons from the traps responsible for the 60 and 140 °C TL peaks in SrAl2O4:Eu2+,Dy3+ and the 80 and 160 °C TL peaks in SrAl2O4:Eu2+,Nd3+ phosphors, respectively.

Thermoluminescence analysis of beta irradiated ZnB2O4: Pr3+ phosphors synthesized by a wet-chemical method

In this paper we describe the thermoluminescence (TL) characteristics of ZnB2O4:Pr3+ phosphors with Pr concentrations varying between 0.2 and 1 mol% prepared by a wet-chemical method. The TL glow curves of the phosphor sample consisted of three peaks located at 71 °C (P1), 124 °C (P2) and 233 °C (P3). The TL intensity increased with the beta dose ranging from ∼0.1 to ∼20 Gy. Dose response, reproducibility and trapping parameters of TL glow curves were evaluated to clearly reveal thermoluminescence features. We observed that TL intensity of P2 and P3 peaks decreases as the heating rate increases. Trap parameters were estimated via the Hoogenstraaten, Booth-Bohun-Parfianovitch, the initial rise methods combined with Tm−Tstop experiment and TLanal CGCD program. Heating rates were varied to use in the Hoogenstraaten analyses. The Tm−Tstop investigations on regenerated TL signals for P1 and P2 peaks indicated that ZnB2O4:Pr3+ phosphor has four electron trap levels with energy values in the range of 0.5–1.5 eV These four traps have first order kinetic and are formed at high temperature region. Resulting values are utilized as a reference for the CGCD procedure and the trapping parameters from the TL glow curves are calculated. The figure of merit (FOM) of the TL glow curve during curve fitting procedures is found to be 2.019%. The intensities of the main dosimetric peaks appeared at 124 °C and 233 °C exhibits good linear dose response up to 20 Gy. These results provide valuable knowledge for use of the characteristics of Pr doped ZnB2O4 in dosimetry research, just need to eliminate low temperature TL peak.

Low temperature thermoluminescence behaviour of Y2O3 nanoparticles

Y2O3 nanoparticles were investigated using low temperature thermoluminescence (TL) experiments. TL glow curve recorded at constant heating rate of 0.4 K/s exhibits seven peaks around 19, 62, 91, 115, 162, 196 and 215 K. Activation energies and characteristics of traps responsible for observed curves were revealed under the light of results of initial rise analyses and Tmax−Tstop experimental methods. Analyses of TL curves obtained at different stopping temperatures resulted in presence of one quasi-continuously distributed trap with activation energies increasing from 18 to 24 meV and six single trapping centers at 49, 117, 315, 409, 651 and 740 meV. Activation energies of all revealed centers were reported in the present paper. Structural characterization of Y2O3 nanoparticles was accomplished using X-ray diffraction and scanning electron microscopy measurements.

Raman and Thermoluminescence Studies of HPHT Synthetic Nanodiamond Powders

Nanocrystalline diamond has received increasing attention because of its unique perspectives in biomedical applications. In this work, Raman and thermoluminescence (TL) properties of commercial synthetic high pressure–high temperature (HPHT) nanodiamond powders with mean size of 60, 140, 380, and 660 nm purchased from PlasmaChem GmbH, Germany are presented. The Raman spectra exhibit a diamond peak related to the CC sp3 chemical bond and a number of additional bands that could be assigned to G‐band, OH and CO groups and some intrinsic point defects. The position of the diamond peak does not depend on nanoparticle size when it is monitored with low power laser. The use of a laser with increased power leads to uncontrolled heating of the nanopowders that is manifested as a broadening and down‐shifting of the 1332 cm−1 line. After exposure to beta radiation, all the powders exhibit a main broad TL peak with maxima between 320 and 380 °C and a weaker low temperature TL. The dose response is linear at the doses of less than 10 Gy for all the powders. At higher doses a supralinear behavior is observed.

Heating rate properties and kinetic parameters of thermoluminescence glow curves of La-doped zinc borate

The aim of this study is to evaluate the effect of different heating rates (HRs) on low and high temperature thermoluminescence (TL) glow-peaks, reusability properties, and the kinetic parameters (activation energy (E), frequency factor (s) and order of kinetics (b)) of 1%, 4% and 10% La-doped ZnB2O4 phosphors. All La-doped ZnB2O4 phosphors have two characteristic TL peaks at around 80–85 °C and 150–160 °C. The experimental results show that the TL glow-peak temperatures (TM) shift to higher temperatures for all doped materials as the HRs increase because of the temperature lag effect. The maximum peak intensity (IM) decreases for the first peak of 1% doped, remains roughly constant for second peak of 1% and both peaks of 4% doped, and increases for both peaks of 10% La-doped ZnB2O4 samples as the HRs increases. Differences between the intensities of various amounts of La-doped phosphors were explained with anomalous HR phenomenon except the first peak of 1% La-doped ZnB2O4 which was clarified by thermal quenching effect. In this study, the temperature dependence of the recombination rate of released carriers during the heating process by increasing the doping concentration of La might explain the peaks of the glow curves, which shows an unexpected behavior with the increasing HR values. In addition, the calculated E values of all doped phosphors were found similar in the range of 0.62 – 1.03 eV for 1%, 0.65 – 1.15 eV for 4%, and 0.69 – 1.01 eV for 10% La-doped phosphors. However, s values were found slightly different related to the dopant amount. Furthermore, different dopant amounts indicate the similar and reasonable properties for the repeated cycles of 5 Gy with the same readout conditions.

Luminescence and low temperature trap centers in mixed rare earth borate crystal

The single crystal of this compound has been grown from melt by using a conventional Czochralski technique. The temperature dependent luminescence spectra were measured using a 265 nm laser as an exciting source in the range of 10–300 K. The scintillation decay time profile was measured and found to have three components. The influence of the trap centers on the luminescence properties was studied by means of thermoluminescence (TL) glow peak analysis. Low temperature TL glow peaks were measured in the temperature range of 10–300 K at the heating rate of 0.1 K/s for X-ray irradiated sample. The TL glow peak consists of two dominant peaks at 88 and 109 K. Several glow peaks with a complex nature causes the decrease in the light yield at temperatures below 250 K, and along with long scintillation decay components were observed. The trap parameters such as activation energy (E), frequency factor (s) and order of kinetics (b) were calculated using various standard methods such as peak shape (PS), variable heating rate (VHR), initial rise (IR) and computerized glow curve deconvolution (CGCD).

Thermoluminescence properties of Al doped ZnO nanoparticles

ZnO nanoparticles doped with aluminum (AZO nanoparticles) were investigated using low temperature thermoluminescence (TL) and structural characterization experiments. TL experiments were performed on AZO nanoparticles in the temperature range of 10–300 K. TL curve presented one intensive peak around 123 K and two overlapped peaks to intensive peak around 85 and 150 K for heating rate of 0.1 K/s. Curve fitting and initial rise methods were used to find the activation energies of associated trapping centers. Analyses resulted in the presence of three centers at 0.05, 0.08 and 0.17 eV with peak maximum temperatures (Tm) of 86.2, 121.5 and 147.1 K, respectively. TL experiments were expanded using different heating rates between 0.1 K/s and 0.5 K/s. Behavior of revealed traps was investigated using an experimental technique called as Tm− Tstop method. It was seen that traps are quasi-continuously distributed within the band gap. Structural properties were studied using x-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy experiments.

Thermoluminescence study of beta irradiated Sr2CeO4:Eu3+ phosphor synthesized using solution-combustion process

Eu3+ doped strontium cerate (Sr2CeO4:Eu3+) phosphor was synthesized by solution - combustion technique using urea as a reducer at initiating temperature of 600 °C. The morphological, structural and thermoluminescence (TL) properties of Sr2CeO4:Eu3+ were investigated. X-ray diffraction patterns revealed the polycrystalline nature of Sr2CeO4:Eu3+ with single phase. The scanning electron microscopy photographs shows that the particle size distributions of all phosphor powders are rather broad with particle diameters in the range from ~ 50 nm to ~ 2 µm. The TL glow curve was found which composed of two well defined peaks at around 323 and 372 K. The electron-trapping properties in terms of TL glow curves are discussed in detail. The TL intensity was recorded for different beta doses and it is seen to increase with increasing doses. A linear behaviour of the TL intensity and peak temperature versus irradiation dose was found for dose up to 185 Gy. The effect of different heating rates was also studied and is seen to cause slight peak temperature shifts. Repeated measurements on the same sample seem not to have any effect on peak temperature positions and TL intensity indicating the sample was stable. Different kinetic parameters like activation energy (E), frequency factor (s) and geometrical factor (μg) were calculated for different TL glow curves. Trap depths were also calculated by different methods including initial rise, variable heating rate and peak shape methods.

REVIEW OF DOSE-RATE EFFECTS IN THE THERMOLUMINESCENCE OF Lif:mg,ti (HARSHAW).

The literature describing the experimental investigations of possible dose-rate effects in the thermoluminescence (TL) of LiF:Mg,Ti (Harshaw) is reviewed. The total lack of glow curve analysis, coupled with inclusion of all or part of the high temperature TL and absence of parallel measurements of possible dose-rate effects in the irradiation stage severely limit the scientific and technical level of the experiments. In addition, the experimental procedures are far from sufficient to warrant any conclusion concerning the presence or absence of dose-rate effects in the TL of LiF:Mg,Ti. This decision is contrary to the widely held belief that there are no dose-rate effects in the TL of LiF:Mg,Ti. In addition, the literature on dose-rate effects in the optical absorption (irradiation stage) of LiF is reviewed and is found contradictory. No dose-rate studies have been carried out on optical absorption in LiF:Mg,Ti. Kinetic simulations demonstrating the possibility, even likelihood, of dose-rate effects are also reviewed. Dose-rate effects are shown to be likely due to competition between excitation and recombination in the irradiation stage. Some other possible mechanisms involving multiple charge carrier trapping are suggested. Further definitive experiments are sorely needed, but the interested researcher should beware, it is not an easy task.

OSL and TL retrospective dosimetry with leucite glass-based dental ceramics

Dental ceramics are radiation sensitive materials and exhibit luminescent properties. Their samples can be potentially used for individual dose assessment in situations where retrospective dosimetry is required. In this work, we investigated dosimetry properties of two leucite glass-based dental ceramics using Optically Stimulated Luminescence (OSL) and Thermoluminescence (TL). We concentrated on characteristics as reproducibility, fading, optical bleaching, minimum detectable dose (MDD), dose response and photon energy response of TL and OSL signals. Both the dental ceramics exhibited very good reproducibility (<5% at 2σ level) when irradiated and measured repeatedly. Their luminescence response was found to be linear for a wide range of doses up to 8.5 Gy. The MDD values for the samples investigated were a few mGy. The ceramics are not tissue equivalent materials, and their luminescent signals measured were strongly dependent on incident photon energy. Because of fading and optical bleaching the OSL and TL signals were not stable in time. Especially optical bleaching represents a main limiting factor for dose reconstruction. However, one of the ceramics provided a relatively resistant high temperature TL peak for dosimetry.

Effect of particle size on the thermoluminescence dosimetric properties of household salt

This work investigates the effect of particle size on the thermoluminescence (TL) response of household salt that is classified into five size fractions between 63 and 250 μm. Irradiation induced two main TL peaks at 110 and 240 °C for each particle size fraction. In addition to these peaks, two additional glow peaks were observed at 80 and 300 °C for particles with small size (<90 μm). The complexity of the glow curve pattern increased with decreasing particle size (<125 μm). The intensity of the main dosimetric TL peak at 240 °C increased with increasing particle size. The maximum beta radiation sensitivity of the salt samples was obtained for the particle sizes of 125–180 and 180–250 μm. For different particle sizes, the stability of the dosimetric TL peaks at room temperature was studied over a storage period of 30 days. No systematic difference in the minimum detectable dose values observed for each grain size fraction and it was found to be 0.4 Gy for each grain size fraction. The kinetic parameters of the dosimetric TL peak were determined for different particle sizes using the initial rise and variable heating rate methods. Moreover, the variations in the glow peaks depending on the heating rate were also analyzed. While an expected behavior of low temperature TL at 110 °C was observed, an interesting heating rate behavior (anti-quenching) of the high temperature dosimetric TL peak at 240 °C was observed.

Thermally and optically stimulated luminescence in long persistent orthorhombic strontium aluminates doped with Eu, Dy and Eu, Nd

The long persistent luminescence, thermoluminescence (TL) and IR stimulated luminescence properties of two orthorhombic strontium aluminates (Sr4Al14O25) co-doped with Eu2+, Dy3+ and Eu2+, Nd3+ exposed to beta radiation is reported. The phosphors were synthesized by the combustion method followed by a post-annealing treatment under a reductive carbon atmosphere. Photoluminescence emission spectra of both phosphors are typical for emission of Eu2+ ions with 7-fold and 10-fold coordination in Sr4Al14025 and consist of the main band at 480 nm and a weak band between 390 and 440 nm. After exposure to beta radiation the Sr4Al14025:Eu2+,Dy3+ phosphor exhibits two strongly overlapped TL peaks at about 70 and 100 °C while the low temperature TL of the Sr4Al14025:Eu2+,Nd3+ phosphor consist of two well separated peaks with maxima at about 60 and 130 °C. Additionally, both phosphors exhibit a weak TL between 180 and 400 °C. The traps responsible for the low temperature TL peaks are the Dy3+ and Nd3+ centers situated in two different Sr sites with 7-fold and 10-fold coordination. The thermal emptying of the Dy and Nd filled traps creates ultra-long intense afterglow, which gradually decays with time and remains detectable after 220 h storage in dark. IR stimulation of beta irradiated phosphors creates intense IR stimulated luminescence, which is related to the release of electrons from the filled Dy and Nd traps.

TL characterization of Ag co-doped SrSO4:Eu phosphor for gamma dosimetry applications

High temperature thermoluminescence (TL) emissions and improvement in fading due to the co-doping ofr Ag in the SrSO4:Eu phosphor synthesized through chemical precipitation technique when subjected to γ-excitation is discussed. The dopant concentrations were tuned for optimum TL sensitivity. Preliminary crystallographic and structural studies of the phosphors were done using PXRD, SEM, and TEM. The phosphor has a single phase orthorhombic lattice structure and the crystallites are found to be nanostructured. The presence of dopants in the host matrix is established through EDS and ICP-AES studies. The TL glow curve shows a single intense emission at 314⁰C under γ- exposure of dose 1Gy, which is given from a 60Co build-up. The dosimetric properties such as sensitivity, dose dependence, fading and reusability of SrSO4:Eu,Ag phosphor were also studied. It is observed that co-doping with Ag improves the fading rate of the SrSO4:Eu phosphor by about 5%. Even though the luminescence intensity is found to be less than that of SrSO4:Eu phosphor, the Ag co-doped phosphor becomes significant owing to its improved fading rate and high temperature afterglow. The gamma sensitivity of the SrSO4:Eu,Ag(0.5,0.5mol%) phosphor is compared to that of the standard CaSO4:Dy TLD phosphor. The TL kinetic parameters were calculated using IR, Chen's peak shape method and verified by the theoretical fit using GCD functions.