Low 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.

Hydrothermal crystal growth of tetralithium octafluoridozirconate (Li4ZrF8) and its physicochemical properties

A single crystal of tetralithium octafluridozirconate (Li4ZrF8) has been obtained by using a hydrothermal process. The crystal phase was analyzed using a powder X-ray diffraction pattern and matched with standard reference data. The high-resolution X-ray diffraction curve indicates that the crystal has good crystalline perfection. The thermal behavior of the crystal sample was investigated by TGA/DSC analysis. The optical bandgap of the crystal sample was calculated from the Tauc plot and found to be 5.8 eV. The crystal sample exhibits intrinsic X-ray excited luminescence with a peak maximum of 265 nm. The thermoluminescence measurement shows two peaks, one is at the high-temperature region of 545 K and another one is at the low-temperature region at 383 K. TL kinetic parameters such as activation energy (E) and frequency factor (s) for the peak at 545 K was estimated as 1.20 eV and 2.06 × 10−10 respectively. The sample has good TL sensitivity to the neutron dose in the order of µsv. The low-temperature thermoluminescence measurements were carried out to study the trap levels and found two major glow peaks at 108 and 130 K. Scintillation properties were analyzed under α-rays from a 241Am source. The decay time profile was well fitted with three components and the fitted values show the fast component of 500 ns (9 %), the medium component of 2.4 μs (24 %), and a slow component of 12.8 μs (67 %).

Low temperature thermoluminescence of β-Ga2O3 scintillator

Low temperature thermoluminescence of β-Ga2O3, β-Ga2O3:Al and β-Ga2O3:Ce has been investigated. Glow curves have been analyzed quantitatively using a rate equations model in order to determine the traps parameters, such as activation energies, capture cross-sections and probabilities of recombination and retrapping.

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.

Scintillation properties of ((CH3)4N)3BiCl6 as a novel lead-free perovskite halide crystal

Two-dimensional hybrid organic-inorganic perovskites (2D-HOIPs) possess intriguing structural properties which makes them promising materials for diverse optical, electronic and scintillation applications. Recently, several classes of hybrid perovskites exhibit potential candidate for radiation detection. However, the scintillation properties of corrugated-type 2D-HOIPs have not been studied so far. In this work, we investigate the scintillation performance of bismuth chloride ((CH3)4N)3BiCl6 perovskites for the lead-free candidate. No strong RL intensity at room temperature is observed due to a strong thermal quenching. A small negative thermal quenching is also observed, which infer the presence of trap states characterized by two activation energies:  = 25.71 meV and  = 129.27 meV. In addition, low temperature afterglow of ((CH3)4N)3BiCl6 at 10 K is estimated to be 70 s (14.5%) and 1200 s (85.5%). In low temperature thermoluminescence ((CH3)4N)3BiCl6 exhibits a broad band, which is attributed to a quasi-continuous distribution of shallow traps. All these results shed some light on the fundamentals of scintillation properties of bismuth-based perovskites.

A simplified multiple aliquot regenerative dose protocol to extend the dating limit of K-feldspar pIRIR signal

The post-infrared infrared stimulated luminescence signal (pIRIR) from K-feldspar shows significantly less athermal fading than the conventional IRSL signal, thus it has been widely used for dating Quaternary deposits. With the single aliquot regenerative dose (SAR) protocol, the test dose signal is influenced by the preceding regenerative dose, and the characteristic saturation dose (D0) of the pIRIR signal is mostly in the range of 200–600 Gy, depending on the size of the test dose. According to the D0 value, the dating range of pIRIR is restricted to <300 ka with the SAR protocol. Here we present a multiple aliquot regenerative dose (MAR) protocol using low-temperature thermoluminescence (TL) signal for inter-aliquot normalisation. The multiple-elevated-temperature (MET) pIRIR signals up to 290 °C are investigated. The D0 increases to 850–1300 Gy with this protocol, which should represent the intrinsic D0 of IR or pIRIR signals of K-feldspar. Based on the higher D0, this protocol has the potential to date samples with equivalent doses (Des) up to 2000 Gy, i.e. up to ∼600 ka considering a dose rate of ∼3.5 Gy·ka−1. Applications of this MAR protocol on two loess samples from the Chinese Loess Plateau provide ages consistent with expected ages up to 350 ka, with the MET-pIRIR signal at 290 °C. However, tests on three fluvial and alluvial samples show age overestimation with the new MAR protocol as well as SAR protocol, which may result from the hard-to-bleach property of the high-temperature pIRIR signals. Simulations of fading correction indicate that the age will be over-corrected when the laboratory dose response curve has a D0 smaller than the true D0 of the signal. Caution should be taken in fading corrected ages measured with the conventional SAR protocol, as the D0 values are always underestimated in this case.

Study of the dosimetric properties of CaSO4:Dy using OSL technique

Calcium sulfate doped with dysprosium (CaSO4:Dy) has been used for personal dosimetry using the thermoluminescence (TL) technique for decades and its TL properties are well-known. Considering the advantages of the OSL technique (relatively simple and faster readout and detector reusability) and the potential applicationof CaSO4:Dy as an OSL detector, this study aimed to investigate the dosimetric properties of CaSO4:Dy using the OSL technique. The present study was carried out using CaSO4:Dy pellets prepared at IPEN irradiated and read in a TL/OSL Risø reader with blue light stimulation and Hoya U-340 filter. OSL dosimetric properties essentially dose response, reproducibility, and fading characteristics were evaluated. Moreover, TL and OSL signals were compared to study the correlation between OSL signals and TL peaks. CaSO4:Dy OSL response is linear from 0.1 to 10 Gy and shows reproducibility better than 5%. The low-temperature TL peak is unstable; however, the OSL signal seems to be associated with higher-temperature peaks.

Radiation-stimulated processes in SrMgF4 single crystals irradiated with fast electrons

Large single crystals of SrMgF4 (SMF), grown by the Bridgman method, were studied (T = 7–350 K, E = 1.2–6.2 eV) for both the pristine unirradiated and irradiated by an electron-beam (Ee = 10 MeV, D = 100–160 kGy, Φmax = 5 × 1015 electrons/cm2) SMF-crystals. The optical absorption spectra at different radiation doses were determined. The luminescence spectra were studied upon excitation with visible/ultraviolet light (PL), or X-ray radiation (XRL). The PL excitation (PLE) spectra under UV-radiation, the temperature dependence curves for the luminescence intensity of steady-state XRL and PL recorded monitoring emission at different energies, as well as low-temperature thermoluminescence were studied. The paper discusses the effect of electron-beam irradiation on the optical and luminescence properties of SMF crystals, the temperature dependence of the luminescence intensity and low-temperature thermoluminescence of irradiated SMF crystals.

Synthesis and spectroscopic characterization of strontium magnesium silicate phosphors for white afterglow applications

Eu 2+ and Dy 3+ ion–activated strontium magnesium silicate phosphors were prepared using a modified solid-state method and two silicon sources: silicon oxide and silicon nitride. Dy 3+ ions were deliberately used to form various trap levels in the host band structure and thus achieve long-lasting performance of the silicate host. The coexistence of Sr 2 MgSi 2 O 7 and Sr 3 MgSi 2 O 8 phases was observed in the X-ray diffraction patterns obtained for phosphors synthesized from various silicon oxide to silicon nitride molar ratios. Photoluminescence spectra contained two broad bands at 464 nm (blue) and 540 nm (yellow) for the same host owing to 4f 7 –4f 6 5d transitions of Eu 2+ ions. The phosphors prepared using higher percentages of silicon nitride exhibited white light emission with chromaticity of (0.28, 0.32). A persistent white afterglow decay time of 10 s was determined using time-resolved spectroscopy for the phosphors prepared using high percentages of silicon nitride. A low-temperature thermoluminescence peak with a trap depth of 0.49 eV and lifetime of 140 s was found to be responsible for the afterglow properties of the strontium magnesium silicate phosphors. The present study demonstrated the suitability of using the obtained silicate phosphors for near-white-afterglow applications.

Semiconductor scintillator development: Pure and doped β-Ga2O3

Our recent research on scintillation properties of β-Ga2O3 crystals, either pure or singly-, doubly-, and triply-doped, obtained with the Czochralski method at the Leibniz-Institut für Kristallzüchtung, is summarized. The results of pulse height, scintillation time profile, and low temperature thermoluminescence measurements are analyzed, mostly in reference to the values of free electron concentration in the samples. Some correlations between particular parameters are found and discussed in order to give hints for a further development of the material.

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.

Thermoluminescence Enhancement of LiMgPO4 Crystal Host by Tb3+ and Tm3+ Trivalent Rare-Earth Ions Co-doping.

We investigated the influence of terbium and thulium trivalent rare-earth (RE) ions co-doping on the luminescent properties enhancement of LiMgPO4 (LMP) crystal host. The studied crystals were grown from the melt by micro-pulling-down (MPD) technique. Luminescent properties of the obtained crystals were investigated by thermoluminescence (TL) method. The most favorable properties and the highest luminescence enhancement were measured for Tb and Tm double doped crystals. A similar luminescence level can be also obtained for Tm, B co-doped samples. In this case, however, the low-temperature TL components have a significant contribution. The measured luminescent spectra showed a typical emission of Tb3+ and Tm3+ ions of an opposite trapping nature, namely the holes and electron-trapping sites, respectively. The most prominent transitions of 5D4 → 7F3 (550 nm for Tb3+) and 1D2 → 3F4 (450 nm for Tm3+) were observed. It was also found that Tb3+ and Tm3+ emissions show temperature dependence in the case of double doped LMP crystal sample, which was not visible in the case of the samples doped with a single RE dopant. At a low temperature range (up to around 290 °C) Tm3+ emission was dominant. At higher temperatures, the electrons occupying Tm3+ sites started to be released giving rise to emissions from Tb-related recombination centers, and emissions from Tm3+ centers simultaneously decreased. At the highest temperatures, emission took place from Tb3+ recombination centers, but only from deeper 5D4 level-related traps which had not been emptied at a lower temperature range.

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 red long-persistent luminescence of Pr3+ doped NaNbO3 with a perovskite structure

Long persistent luminescence (LPL) phosphors can keep emitting light after the removal of excitation sources under thermal disturbances at room temperature, which provides a wide application from emergency signs to in vivo biological imaging. Unfortunately, these phosphors will exhibit poor LPL performance once the thermal activation energy is not sufficient to release the captured carriers from the traps at low-temperature. Herein, a red phosphor of Pr3+ doped NaNbO3 with a perovskite structure is designed, which realizes a low-temperature LPL. The red emission (λem = 612 nm) is ascribed to the 1D2→3H4 transition of Pr3+ ions, and LPL can be visually recognized over 16 h after the removal of the excitation source at 200 K. Low-temperature thermoluminescence curves, temperature-dependent photoluminescence spectra indicate that abundant traps (≤ 0.6 eV) exist in NaNbO3: Pr3+, which is critical for ensuring the low-temperature LPL. The investigation on low-temperature LPL properties of NaNbO3: Pr3+ helps us to reveal the importance of defects structure, and provides new opportunities in exploring luminescence materials applied in an extreme conditions.

Low temperature thermoluminescence anomaly of LiF:Mg,Cu,P radiation detectors exposed to 1H and 4He ions

Lithium fluoride thermoluminescent radiation detectors with different dopant concentrations (7LiF:Mg,Ti and 7LiF:Mg,Cu,P) were exposed to 1H and 4He ions at the Heavy Ion Medical Accelerator in Chiba (HIMAC) in order to investigate their response to energetic light charged particles. Computer simulations with the Monte Carlo code PHITS were performed for a better interpretation of the experimental data. The results were compared with literature efficiency data and with the results of a recently developed microdosimetric efficiency model. In case of the main peak signal of 7LiF:Mg,Ti detectors, the determined efficiency values are in good agreement with previous investigations. Discrepancies in the efficiency of high temperature signal due to well-known non-linearity effects are reported. For 7LiF:Mg,Cu,P detectors, an anomalous thermoluminescence behavior in the low temperature part of the signal was found and discussed. Depending on the light quantification process, differences up to 30% in the dose assessment can be obtained, affecting also the relative efficiency determination process. An explanation of this phenomenon as a consequence of local migration of the charged carriers between the low temperature peaks and the main peak is presented. The implications of these findings on the use of LiF:Mg,Cu,P detectors in radiation environments characterized by the presence of 1H and 4He ions (i.e. space and proton therapy) are discussed. In order to avoid the occurrence of this anomalous behavior, it is advised to pre-heat the detectors after energetic light particle exposures.

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.

Radioluminescence, low temperature thermoluminescence and scintillation properties of Ca and Eu doped ZnWO4 single crystals

In this work, radioluminescence, low temperature thermoluminescence, and light yield of ZnWO4, ZnWO4:Ca, and ZnWO4:Ca, Eu single crystals is reported. It is shown that although the single doping with Ca improves, in a limited scope, the scintillation properties of the studied material, it is not the case with the double doping with Ca and Eu. The values of light yield and energy resolution of the investigated ZnWO4:Ca, Eu samples are clearly worse compared to either ZnWO4 or ZnWO4:Ca. The X-ray excited spectra of all the crystals, dominated by the intrinsic luminescence, unveil a strong decrease of intensity from 10 to 350 K; the addition of Eu does not improve this property. Furthermore, the presence of Eu strongly influences the low temperature glow curves, i. a. by introducing a distinct peak close to 150 K.

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.