Thermoluminescence Glow Peak Research Articles

Structural and optical studies of CaSO4:Ce3+ nanorods for display and dosimetric applications

The CaSO4:Ce3+ (1-9mol%) nanorods were successfully synthesized by co-precipitation method. Preliminary crystallographic, structural and optical studies of the prepared nanorods were done using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), Fourier transform infrared spectroscopy (FTIR), UV-visible absorption spectroscopy, photoluminescence (PL) and thermoluminescence (TL). The CaSO4:Ce3+ has a single phase hexagonal lattice structure with space group P3121(152). The average crystallite size was calculated using Scherrer’s formula and found to be in the range 41-62 nm which is in good agreement with TEM results. The SEM micrographs shows rod like structure with various sizes. Upon 350 nm excitation, the CaSO4:Ce3+ nanophosphor showed emission at 390, 405 and 430 nm, which is characteristic luminescence of $5{\rm d} \rightarrow 4{\rm f}$ (2F5/2, 2F7/2) transitions of the Ce3+ ions. The chromaticity co-ordinates and correlated color temperature of all the phosphors were well located in blue region. TL glow curve response of the prepared nanorods with 500 Gy $\gamma$ -irradiated was studied. TL glow curve contains glow peak at 188 °C. Kinetic parameters was estimated for deconvoluted TL glow peaks and studied in detail.

Trap level analysis of Ce3+ and Sm3+ in Li6Y(BO3)3

Abstract The polycrystalline compounds of Li6Y(BO3)3: Ce3+ and Sm3+ co-doped polycrystalline samples were prepared by using standard solid state reaction method. The energy levels of the doped lanthanide ions (Ce3+ and Sm3+) in the borate host materials were investigated by Thermoluminescence (TL) glow peak analysis. The co-doped samples, exhibits the TL peak at higher temperature region around 511 K whereas the Ce3+ individually doped sample has peak around 433 K. The X-ray excited emission spectra were carried out for all the prepared samples and found the characteristic emission bands. The trap depths (E) were calculated by using several standard methods, namely peak shape method or chen's (PS), variable heating rate (VHR), initial rise (IR) and computerized glow curve deconvolution (CGCD). The mean activation energy of the co-doped samples found to be 1.21 (0.07±) eV and the frequency factor around 1.38 × 1011 Sec−1. The calculated trap depths and the predicted energy level values were compared and found in good agreement. This primarily results suggest that the energy level scheme can help in the development of new TL materials suitable in dosimetry.

Thermoluminescence spectra of Tm doped ZnB2O4 phosphor prepared via a wet-chemical synthesis

In this paper we describe the thermoluminescence (TL) characteristics of 0.8 mol% Tm3+ doped ZnB2O4phosphors prepared by a wet-chemical method. The TL glow curves of the phosphor sample consisted of three peaks located at 181 °C, 213 °C and 351 °C. The glow peak TL temperature (Tm) at which the TL glow peak occurs shifts toward the higher temperature side whilst the heating ramp rate increases and also the peak TL intensity (Im) decreases. The TL glow curves are characterized by evaluating various dosimetric characteristics of scrutinized samples. The Tm−Tstopinvestigations on regenerated TL signals revealed that there are five different traps in the phosphor with energy values in the range of 0.61–1.71 eV. The dose responses increased in a linear way for 3 peaks with the beta-ray exposure in the dose range of 0.11–60 Gy. The process of applying 10 Gy dose was repeated for ten successive irradiation cycles to check reproducibility and the maximum variation was found to be less than 1% from the average value. These results provide valuable knowledge for use of the characteristics of Tm doped ZnB2O4 in dosimetry research.

Influence of surface modification on enhancement of luminescent properties of SiO2@SrTiO3:Dy3+ nanopowders: Probe for visualization of sweat pores present in latent fingerprints

The paper reports, novel SiO2@SrTiO3: Dy3+ (5 mol %) nanopowders fabricated via the low temperature sonochemical route by utilizing bio-surfactant Aloe Vera gel extract. The powder X-ray diffraction results display intense and narrow peaks confirm the monoclinic phase of SrTiO3. The photoluminescence emission spectra of SrTiO3:Dy3+ (5 mol %) with different layers of SiO2 coating display intense and characteristic peaks at ˜ 483 nm (4F9/2 → 6H15/2), 576 nm (4F9/2 → 6H13/2) and 664 nm (4F9/2 → 6H11/2). The broad thermoluminescence glow peak with maximum intensity at ˜ 200 °C for both with and without coated SrTiO3:Dy3+ (5 mol %) nanopowders was noticed. The optimized SiO2@SrTiO3:Dy3+ (5 mol %) nanopowders was most suitable for visualization of the latent fingerprints, revealing explicit specific ridge characteristics, including level I -III. Therefore, the present work opens a new possibility of use of prepared nanopowders for WLEDs, visualization of latent fingerprints and dosimetry applications.

Simulation of an Anomalous Behavior of Thermoluminescence Glow Peak of Quartz from Nigeria

Simulation of an Anomalous Behavior of Thermoluminescence Glow Peak of Quartz from Nigeria

Long persistent luminescence and blue photochromism in Eu2+-Dy3+ co-doped barium silicate glass ceramic phosphor

Eu2+-Dy3+ co-doped barium silicate glass was prepared by a melt quenching method and cerammed at various temperatures between 800 and 1250 °C to obtain the glass ceramic (GC) persistent phosphors. The crystal phase of Ba5Si8O21 was primarily precipitated in the GC samples. The GC sample cerammed at 1250 °C (GC1250) exhibited the longest persistent luminescence over 16 h until the luminance becomes 2 mcd/m2. The color of GC1250 sample was changed from white to blue after UV light illumination, and then bleached efficiently by red light (660 nm) illumination or heat treatment at 200 °C. From thermoluminescence (TL) glow curve measurements, four different TL glow peaks were observed at 191 K, 278 K, 446 K, and 494 K. On the other hand, after red-illumination following UV-illumination, the TL intensity of the only 446 K-peak was selectively decreased in the TL glow curve. It was shown that the blue photochromism of GC 1250 sample is due to an electron trapping defect strongly related with this glow peak.

Thermoluminescence properties of Tb3+-doped CaO–Al2O3–B2O3-based glasses

In this study, the thermoluminescence (TL) characteristics and X-ray radiation response properties of 35CaO–15Al2O3–50B2O3:xTb4O7 (x = 0.25, 0.5, 1.0, 2.0, and 4.0 mol%) glasses were evaluated. These glasses, prepared by a conventional quenching method, were transparent and non-hygroscopic. The TL spectra showed a green band emission (400–600 nm) arising from 4fn–4fn forbidden transitions of the Tb3+ ions. A TL glow peak was observed at 360 K in all the glasses at different Tb concentrations. Among them, the 1.0, 2.0, and 4.0 mol% Tb-doped glasses exhibited excellent linearity over the 1.0 mGy–10 Gy irradiation dose range. The TL peak intensity decreased to ∼60% after 1 h, ∼45% after 24 h and ∼30% after 72 h.

Synthesis and thermoluminescence studies of UV-C exposed Li4Ca(BO3)2: Dy3+ phosphors

Thermoluminescence (TL) response of trivalent dysprosium ion doped Li4Ca(BO3)2 phosphor prepared by combustion method was studied. The samples were exposed to ultraviolet (UV-C) radiation (254 nm). The orthorhombic crystal structure of the Dy3+ doped Li4Ca(BO3)2 nanophosphors was confirmed by X-Ray diffraction patterns. The TL glow curves showed a broad peak around 419 K with a shoulder around 482 K. The dose response curve of Dy3+ doped Li4Ca(BO3)2 phosphor was studied by exposing the optimized sample for different exposure time ranging from 30 min to 5 h at the heating rate of 10 K/s. A shift of the peak towards higher temperature with an increase in dose indicates that the TL glow peak obeyed a non-first order kinetics. The TL intensity was also found to increase with increase in heating rate. The trapping parameters such as activation energy, order of kinetics were also calculated by using Chen's peak shape method. The optical and thermal fading of UV-C (254 nm) exposed Dy3+ doped Li4Ca(BO3)2 have been studied. Experimental results suggest the Dy3+ doped Li4Ca(BO3)2 as a good candidate to be employed as a complementary thermoluminescent devices.

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.

X-ray irradiated thermo- and radioluminescence, structural and thermal characterization of septarian (powder&bulk) from Madagascar

The luminescence properties of septarian have been investigated for the first time in this study, which has been the subject of many studies in both geological and geophysical fields. This sediment with a calcium carbonate structure exhibited high luminescence properties with X-ray excitation. The radioluminescence (RL) and thermoluminescence (TL) properties were investigated as well as their structural (FT-IR, XRD), morphological (SEM), thermal (TG-DTA) and absorption (UV-Vis-NIR) properties of this sediment. The broad RL peak of septarian was observed at 640 nm. There was a significant increase in the RL intensities of the sifted samples compared with the bulk sample. The TL glow curves of septarian irradiated with X-rays exhibited intense main TL glow peak having the maximum temperatures at 116 °C and about 390 °C with a heating rate of 2 °C/s. Also; the TL kinetic parameters were reported; activation energy (E), frequency factor (s) and the order of kinetics (b) of the first peak have been determined in detail by using peak shape (PS) and Computerized Glow Curve Deconvolution (CGCD) methods. SEM and EDS analysis were performed for the two different layers of septarian. The light colored side with the amorphous structure of the sample has more impurities (such as Fe, Al, Zr, K) than the crystallized and darker side.

Determination of thermoluminescence kinetic parameters of white and blue chalcedony exposed to X-ray irradiation

The study reveals the thermoluminescence (TL) properties of white and blue chalcedony minerals which this mineral mined two different regions (Edirne and Eskişehir, respectively) of Turkey. With the help of various characterization techniques (such as X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR)), the gem-quality of the samples was tested. The TL glow curves of the samples irradiated with X-rays show intense main TL glow peak having the maximum temperatures at 100 °C and 121 °C with a heating rate of 2 °C/s, respectively. The TL kinetic parameters of the samples are reported here for the first time. Activation energy (E), frequency factor (s) and the order of kinetics (b) of these peaks have been determined in detail by using various heating rates (VHR) and peak shape (PS) methods and verified by Computerized Glow Curve Deconvolution (CGCD). The CGCD method was used to determine the number of peaks associated with the TL glow curves. The values of E calculated with these three methods are a good agreement.

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).

Influence of annealing on thermoluminescence of natural quartz: Kinetic analysis and experimental study of apparent inverse thermal quenching

The influence of annealing on the main thermoluminescence glow-peak of natural quartz is reported. For comparison, results from un-annealed quartz are included. The glow-curve measured at 1 °Cs−1 after beta irradiation to 50 Gy revealed six peaks each for quartz annealed at 800 °C for 1 h and the un-annealed sample. The main peak in both quartzes was observed at 72 °C. This report focusses on kinetic analysis of the main peak. The analysis was carried out using various methods consisting of the initial rise, whole glow-peak, peak shape, variable heating rate and phosphorescence-based methods. The activation energy obtained using the various methods ranges between 0.91±0.01eV and 1.19±0.03eV for the annealed sample and between 0.93±0.01eV and 1.26±0.12eV for the un-annealed sample. The result suggests that annealing has little effect on the activation energy. The luminescence intensity decreased with heating rate in the un-annealed sample in a manner suggestive of thermal quenching. In contrast, the dependence of intensity on heating rate in the annealed sample is influenced by the dose the sample is irradiated to. Whereas thermal quenching was noted for a dose of 50 Gy in the un-annealed sample, the annealed sample showed evidence of thermal quenching at a low dose of 3 Gy with the opposite effect when irradiated to 50 Gy. The activation energies of thermal quenching were found as 0.89±0.06eV and 0.99±0.02eV for the un-annealed and annealed samples respectively. We ascribe the apparent dependence of thermal quenching on dose in the annealed sample to competition between radiative and non-radiative transitions at the recombination centre.

Enhanced persistent red luminescence in Mn2+-doped (Mg,Zn)GeO3 by electron trap and conduction band engineering

The effect of Zn substitution on the persistent luminescence properties of MgGeO3:Mn2+-Ln3+ (Ln = Eu and Yb) red phosphors was investigated. The intensity of the persistent luminescence of the Eu3+ co-doped phosphors increased with increasing Zn content, whereas that of the Yb3+ co-doped samples decreased. For both series of lanthanide co-doped samples, the thermoluminescence (TL) glow peak shifted to the lower temperature side with increasing Zn content. These persistent luminescence properties were well explained in terms of lowering of the bottom of the conduction band relative to the ground state of the divalent lanthanide ions. Especially, in Eu3+ co-doped system, TL peak shifted from 520 K to 318 K by 50% Zn substitution. The persistent radiance of the (Mg0.5 Zn0.5)GeO3: Mn2+-Eu3+ sample at 1 h after ceasing UV light was 46 times stronger than that of MgGeO3:Mn2+-Eu3+, and 11 times stronger than that of ZnGa2O4: Cr3+ standard deep red persistent phosphor.

SYNTHESIS, OPTICAL PROPERTIES AND THERMOLUMINESCENCE DOSIMETRY FEATURES OF MANGANESE DOPED Li2B4O7 NANOPARTICLES.

Lithium tetraborate (Li2B4O7) nanoparticles (NPs) doped with manganese (Mn) were prepared for the first time by the solid-state sintering method. NPs were characterized using X-ray diffraction, scanning electron microscopy, photoluminescence and thermoluminescence (TL) techniques. The synthesized NPs exhibited highest TL response at 0.3 wt% of Mn dopant under gamma irradiation. TL dose response is linear for the absorbed dose from 1 Gy to 20 kGy and beyond this range behaves sub-linear. Such feature makes the synthesized nanophosphor as a promising material for high-dose dosimetry applications. Low fading and good reusability were obtained for the synthesized NPs. Tm-Tstop and computerized glow curve deconvolution procedures were utilized to identify the component TL glow peaks and kinetic parameters of the produced phosphor. Other TL dosimetry features of the prepared NPs are also presented and discussed.

Synthesis and dosimetry features of novel sensitive thermoluminescent phosphor of LiF doped with Mg and Dy impurities

Lithium fluoride doped with Mg and Dy was fabricated for the first time using melting method. The optimum concentrations of impurities and thermal treatment were studied to achieve high thermoluminescence (TL) sensitivity. TL sensitivity of the fabricated phosphor is close to that of TLD-100 powder. Tm-Tstop technique was used to identify the number of overlapped TL glow peaks. Initial rise, isothermal decay and computerized glow curve deconvolution (CGCD) methods were applied to obtain kinetic parameters of the prepared TL material. Three component glow peaks were distinguished at temperatures 395, 448 and 510 K. Other TL properties such as fading, linearity of dose response and reusability are also presented and discussed.

Luminescent properties of Eu3+ co-doped Y2O3: Dy3+ phosphors synthesized via ceramic route

The Eu3+ co-doped Y2O3: Dy3+ phosphors were synthesized by solid-state reaction method, also known as a ceramic route. The properties of synthesized phosphors were studied with the help of PXRD, SEM, EDX, FTIR, Photoluminescence (PL) spectra, CIE coordinates and Thermoluminescent (TL) spectra. The PL spectra exhibit emissions at 486, 588, 596, 610, 681 and 693 nm due to the energy transfer between dopant ions. The blue emission is dominated due to dysprosium ions. The TL spectra were recorded for synthesized phosphors irradiated by UV and γ radiation. For UV irradiated phosphors, TL glow peaks were obtained at 455, 490 and 549 K whereas for γ irradiated phosphors TL glow peaks were obtained at 470 and 650 K. Using deconvoluted TL curves, kinetic parameters were computed by peak shape method. Second order kinetics were obtained with activation energy values varying from 7.553 × 10− 1 to 11.10 × 10− 1 eV for UV irradiated phosphors and 11.152 × 10− 1 to 15.252 × 10− 1 eV for γ irradiated phosphors.

A luminescence spectroscopy study of new Li2BaAl2F10 single crystal

Large Li2BaAl2F10 single crystals of optical quality were grown using the vertical Bridgman method. X-ray diffraction method was used to determine the crystal structure (orthorhombic symmetry Cmc21), lattice parameters, atomic coordinates. The luminescent properties were investigated using selective photoexcitation by synchrotron radiation (E = 3.7–21 eV, T = 8 K, time integrated and time-resolved spectra) as well as upon excitation with unfiltered X-ray beam (synchrotron radiation or X-ray tube). We revealed both the broadband luminescence at E m = 4.0 eV (E ex=11.72 eV) attributed to the radiative annihilation of self-trapped excitons (STE) and the excitonic-type near-defect luminescence at E m = 3.0–3.2 eV (E ex=11.25 eV) attributed to radiative relaxation of electronic excitations in nonequivalent structural units of the crystal lattice. The fast exponential component with lifetime of 5.6 ns, a low-intensity intermediate component with a lifetime of 75–100 ns, a constant level — pedestal (sum of the micro- and millisecond decay components) were revealed in luminescence decay kinetics. The electronic structure parameters (bandgap E g = 13.0 eV, low-energy onset of the intrinsic host absorption E c = 11.2 eV), the energy threshold for the excitation of STE-luminescence (E th = 11.2 eV) are determined from spectroscopic data. Thermoluminescence (TL) has been studied (90–350 K) using spectral-integral regime. Four partially overlapping TL glow peaks were revealed, their deconvolution was done and thermal activation parameters were determined using TGCD method.

Radiophotoluminescence and thermoluminescence characteristics of undoped and Mg doped LiF phosphor in the high dose region

Radiophotoluminescence (RPL) and thermoluminescence (TL) from undoped and Mg-doped LiF powder samples were investigated for high dose dosimetric applications. F-aggregate centres in LiF are created by radiolysis. The RPL emission at 530 nm and 650 nm from F3+ and F2 centres respectively (on excitation at 450 nm) in undoped commercial LiF powder enhanced with increasing sintering temperature. Its TL glow curve showed peaks at 145, 290 and 365 °C. The RPL-TL correlation studies carried out for the first time showed that the thermal annihilation of F3+ and F2 centes following Fi0 - Va (interstitial-vacancy) recombination cause 290 °C and 365° TL peaks respectively. This showed that F2 centres are thermally more stable than F3+ centres. Its integrated TL response kept increasing nearly linearly up to 14 kGy, in contrast to the response of the TL peaks in dosimetry grade LiF:Mg, Ti (TLD-100). However, the TL from LiF suffers from fading problems. A 100 °C, 15 min pre-read annealing treatment erased most of the 145 °C TL peak without disturbing the other high temperature peaks. A 750° C, 22 h sintering treatment in carbon atmosphere shifted the major TL glow peak of undoped LiF to 200 °C but reduced its TL sensitivity by more than a factor of 10. Mg-doped LiF samples exhibit a TL glow curve peaking at ∼240 °C with satellite peaks typical of Mg doped LiF whose shape did not change significantly with gamma dose. However it showed lower TL and RPL sensitivities as compared to those of undoped LiF. All LiF except LiF alfa (750 °C, 1 h, CB) showed sublinear increase in TL with dose and therefore will cause inaccuracy in dose measurements especially at high doses due to reduced sensitivity. LiF alfa 750 °C, 22 h and 1000 °C, 6 min sintered powder samples are better than others because their RPL sensitivity increases nearly linearly with dose. However, a low fading observed in the latter sample supports its application. The bright yellow RPL emission seen through a 550 nm cut on filter illuminated with a 450 nm blue LED or He-Cd laser light could quickly confirm an irradiated consignment on which LiF samples are affixed. The increase in green to red emission ratio with dose and post-irradiation storage period might be related to slow migration of anion vacancies created by one secondary electron track to F centres created by another track and consequent conversion of F2 → F3+ centres.

Thermoluminescence dose and heating rate dependence and kinetic analysis of ZnB 2 O 4 :0.05Dy 3+ phosphor

Abstract The intention of this study is to explore the thermoluminescence (TL) behavior of beta irradiated 5% Dy3+ doped zinc borate (Zn(BO2)2:0.05Dy3+) phosphor prepared using the nitric acid method. The TL glow curve corresponding from 1 Gy to 80 Gy beta irradiation (preheated at 140 °C) shows a maxima at c.a. 180 °C. The dependence of heating rate was tested and found out that thermal quenching effect was dominating on TL glow curves as the heating rate increases. The dose response of the phosphor material exposed to beta radiation was investigated. Deconvolution was applied using the peak fit method on the glow curve for optimized conditions. Also peak shape (PS), various heating rates (VHR) and computerized glow curve deconvolution (CGCD) methods were used to evaluate the trapping level parameters, namely trap depth (E), frequency factor (s) and order of kinetics (b) associated with the main glow curve in Zn(BO2)2:0.05Dy3+ phosphor after beta irradiation of 20 Gy. The values of trap depth corresponding with the TL glow peak at 180 °C were found to be 0.93 eV, 0.92 ± 0.05 and 1.05 ± 0.02 respectively. Furthermore W and c parameters characterizing thermal quenching based on the Mott-Seitz theory were determined as 0.31 ± 0.04 eV and 162.55. The TL mechanism appears more likely to get second order kinetics, suggesting the probability of re-trapping of charge carriers by emptied traps.