Thermoluminescence Peak Research Articles

On the application of the various heating rate method to determine the activation energy of the dominant trap from a complex TL peak

The various heating rate (VHR) method is used to determine the activation energy (E) of traps responsible for thermoluminescence (TL) peaks. The VHR method was developed and works well for single glow peaks. However, it is often applied to multiple overlapping peaks where one of the peaks is dominant. The use of VHR method for TL curves consisting of several peaks for determining the activation energy of the dominant peak may, due to an arbitrary selection of the heating rate set adopted for calculations, lead to a different result than the actual physical value of this parameter. The purpose of this work is to show how different results can be obtained using various heating rate sets in the VHR method for curves composed of two peaks with one clearly dominant. The method was used for several examples of TL curves generated numerically in such a way that the impact of the ratio of peak intensities, or peak mutual position on determining the energy may be observed.

Thermoluminescence and optically stimulated luminescence properties of ulexite mineral

Although naturally occurring luminescence materials such as quartz and feldspars are generally used for radiation dosimetry and dating, natural borates may also stand as a promising material for dosimetry and dating. We report thermoluminescence (TL) and optically stimulated luminescence (OSL) of one of the most abundant boron minerals in Turkey namely, ulexite (NaCaB5O6(OH)6·5H2O). An X-ray diffraction (XRD) analysis confirmed that the sample has triclinic crystal structure and contains 40.55% of B, 5.92% of Na2O, 12.3% of CaO. A thermogravimetric analysis indicates two stages of dehydration within 60–160 °C, 160–250 °C and dehydroxylation within 260–580 °C. Analysis of TL glow curves using fractional glow and deconvolution reveal that there are four glow peaks at 154, 211, 273 and 327 °C in the glow curve of ulexite. All the glow peaks follow a non-first order kinetics. The activation energies of the traps are estimated from the fractional glow curves as 0.72, 0.93, 1.16 and 1.28 eV and that evaluated from the deconvolution analysis as 0.76, 0.83, 0.96 and 1.27 eV. The lifetimes of these traps are estimated within 1.55 days–3.6 × 104 years. The radiation dose responses of the TL peaks are supra-linear between 8 Gy and 1024 Gy. OSL decay curve of ulexite consists a fast, a medium and a slow component with recombination lifetimes of (0.63 ± 0.08), (7.51 ± 0.71), (93.49 ± 3.62) s respectively. The fast OSL component obeyed first order, whereas medium and slow components obeyed general order of kinetics. The dose response of the medium and slow OSL components showed a sub-linearity from 64 Gy to 4096 Gy whereas the fast component showed linear response between 8 and 4096 Gy.

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.

Effect of Ge:Si ratio and charging energy on carriers trapping in Y2(Ge,Si)O5:Pr powders observed with thermoluminescence methods

Oxyorthosilicates have long history in luminescent applications e.g. as phosphors, scintillators and in emerging technologies like luminescence thermometry. In this study we report detailed research on the thermoluminescent (TL) properties of Y2(Gex,Si1-x)O5:Pr. Despite regular TL measurements, Tmax-Tstop, initial rise analysis, fading, decay of persistent luminescence, and dose effect are presented and analyzed. The possibility to deliberately manage the electron trap depths adjusting the Ge/Si ratio is explored. Glow curve of each composition consists of two main TL peaks. In the (Ge,Si) solid continuous distribution of trap energies is observed. Strong thermoluminescence is observed from all compositions after charging with X-ray radiation. Efficiency of charging traps with UV-C photons (fitting the 4f→5d1 transition energy) lowers systematically as the Si content increases. A growing coupling of the excited 5d1 level of Pr3+ and the host conduction band with the increase of Ge content is responsible for this effect. A scheme of the TL-related processes is presented using the vacuum referred binding energy (VRBE) approach for all the Y2(Gex,Si1-x)O5:Pr phosphors.

Radiation Induced Defects and Thermoluminescence Characteristics in Eu, Dy and Eu/Dy Doped-Quartz Sol-Gel by 2 Gy Beta and 2 MeV ⁴He⁺ Irradiations

Thermoluminescence (TL) of pure and Eu3+ and Dy3+ doped synthesis quartz was synthesized and their ion beam and thermoluminescence properties were investigated. The as prepared, doped and co-doped quartz and the effects of imparting 2 Gy beta dose and 2MeV 4He+ ion beam irradiation is investigated. The basic model proposed and can explain our observations is that, the dominant signals from the as prepared material arise from the incorporation of the transitions within the RE dopants enhanced by the intensity from the intrinsic or host defect sites within the synthesis quartz network. The complex shape TL glow curves indicate that irradiation causes major distortions to the lattice with the incorporation of extrinsic impurities and RE doping processes, induce perturbations and alter the energy levels pattern of the free ions and assigned transitions probabilities in a manner that that depends on the dopants, their concentrations and the host material. The larger Eu ions stabilize the emission more than that of the Dy ions. The TL peak temperatures are commonly correlated via charge transfer processes and scale with the ions size, in such a manner that the close proximity (or shallow traps) allows lower temperature electron release, whereas the more distant variants (deep traps) are less distorted, but are still able to couple to the higher energy orbitals of the Eu ions.

A cryogenic setup for multifunctional characterization of luminescence and scintillation properties of single crystals.

This article reports on a cryogenic setup that can be used for multifunctional experimental purposes. The temperature of the setup can be set from 10 K to 300 K. Different kinds of experiments were carried out in this experimental setup such as (1) luminescence emission, light yield, and decay time measurement under excitation of 266 nm laser and 280 nm LED sources, (2) thermoluminescence (TL) measurement under an x-ray excitation source, (3) scintillation property measurements such as light output, energy resolution, and decay time under 137Cs (662 keV γ-rays) and 241Am (5.4 MeV α) isotope sources, and (4) scintillation measurement under a 90Sr beta source through the continuous single-photon counting technique. The luminescence and scintillation properties of various molybdate and tungstate crystals such as CaMoO4, Na2Mo2O7, Pb2MoO5, CdWO4, and ZnWO4 are characterized and reported in the present work. The TL measurement of a CaMoO4 crystal is carried out from 10 K to 300 K, and various kinetic parameters such as order of kinetics, frequency factor, activation energy, and figure of merit are calculated for different TL peaks. As the temperature goes down from room to 10 K, the light yield of all studied crystals increases. Since the light yield of the crystal increases as temperature decreases toward 10 K, this experimental setup can be used for the characterization of luminescence and scintillation properties of a single crystal for rare event searches such as neutrinoless double-beta decay and dark matter.

Spectrally Resolved Thermoluminescence of Anion‐Deficient Al2O3–BeO Ceramics for High‐Dose Dosimetry

Thermoluminescence (TL) curves of Al2O3–BeO ceramic samples synthesized during high‐temperature treatment of nanostructured Al2O3 compacts in vacuum with the presence of graphite in BeO crucibles are studied. Temperature ranges of certain TL peaks emission at the synthesis temperature varied from 1200 to 1400 °C are found. A comparative analysis of the TL peaks temperature position and the nature of traps in the obtained ceramics with single crystalline Al2O3, BeO, and BeAl2O4 analogs is carried out. Spectral composition of different TL peaks is investigated. It is found that oxygen vacancies and their aggregates play the main role in the TL emission centers formation in the samples under study. A complex structure of the dominating luminescence band at 4.0 eV in the dosimetric peak at 530 K of the ceramics synthesized at 1400 °C is found. This band is shown to be a superposition of three bands with the maxima at 3.11, 3.80, and 4.17 eV, resulted from F, F+ centers and presumably from Fcat‐type centers in aluminum oxide. The obtained results are essential to control and modify TL properties of Al2O3–BeO ceramics to create luminescence detectors of high‐dose radiation.

Luminescence sites and spectra of metal doped microwave synthesized Mg2SiO4:Tb

Terbium doped magnesium orthosilicate (Mg2SiO4: Tb) has been reported as the most efficient thermoluminescence dosimeter material. Further sensitivity improvements of Mg2SiO4: Tb may be achieved by co-doping with other metal ions. Performance is strongly influenced by the sintering conditions, as shown here for Mg2SiO4: Tb samples which were synthesized with microwave thermal processing. A series of Mg2SiO4: x mol% Tb (x = 0.5, 1, 3, 5, 7) and Mg2SiO4: Tb, M (M = Li, Na, Ca, Al, Ga) samples are compared. Photoluminescence (PL) and Thermoluminescence (TL) of all samples are dominated by the characteristic emission of Tb3+. Co-doping can improve the sensitivity, and this is linked to modification of the micro-structure, as revealed by SEM measurements. Among the co-doped samples investigated, Mg2SiO4: Tb, Na shows the highest TL response with the main TL peak at 196oC. Differences between processing with microwave heating and thermal sintering are apparent in terms of the association of the dopants. Benefits and future possibilities with wider applications are discussed.

Thermoluminescence properties of unique Rosso Levanto marble

This marble extracted from deposits in Elazığ in Turkey resembles red meat in appearance and is only found in Elazığ. This type of marble has been widely used in the most famous architectural structures and buildings. In this study, the thermoluminescence (TL) properties of a unique marble that originated from Turkey, named Rosso Levanto, were investigated. Two distinct TL peaks were observed at 160°C and around 375°C. Particle size experiments showed that best TL intensity was seen at 200 μm particle size and therefore dose-response, heating rate, cycle of measurement and fading experiments were carried out on powdered samples with a particle size of 200 μm. The findings revealed good linearity in dose-response, observed up to 0.5 kGy. The reproducibility experiment gave good results, but peak intensity decreased by about 40% in first 6 h of storage in a dark room.

Correlation between thermoluminescence and optically stimulated luminescence responses of natural alexandrite

Luminescent properties of alexandrite crystals (BeAl2O4:Cr3+) are studied. Partial readouts of thermoluminescence (TL) and optically stimulated luminescence (OSL) signals were obtained to infer the relations of OSL and TL trapping centers. Four TL peaks were studied; their intensities decrease at different rates by illumination with blue OSL light. The OSL curve shows two-time components (exponential decay constants 3.15 and 28.4 s). The short time component is preferentially diminished when the sample is heated to temperatures from 363 to 513 K. About 50% of the whole TL intensity remains after a complete 300s OSL readout.

Cerium-doped lithium tetraborate for thermoluminescent dosimetry

This work presents the preliminary structural and dosimetric analyses of tissue-equivalent Li2B4O7:Ce pellets prepared by solid state synthesis. X-ray diffraction was performed in order to confirm the crystalline phase of Li2B4O7. The dosimetric analyses were done by exposing the pellets to a beta source and using the thermoluminescent technique. The results showed that the thermoluminescent (TL) signals of the pellets present a good reproducibility. The TL peak at 233 °C has negligible fading and the TL dose response is linear in the range from 41 mGy to 42 Gy. These characteristics indicate that the Li2B4O7:Ce pellets produced in this work have potential for use as a thermoluminescent dosimeter.

The effect of dose on thermoluminescence of ScPO4:Eu3+ ceramic

Depending on the dose of ionizing radiation, ScPO4:0.1%Eu3+ sintered ceramic presents significantly different thermoluminescent properties. Despite a thermoluminescent peak around 90 °C which appears upon small doses (up to tens of mGy) it also shows strong thermoluminescence at 240 °C but only after exposure to higher doses. In both cases, the thermoluminescence is generated by Eu3+ ions, which also serve as electron traps. Recognition of the relevant hole traps responsible for the thermoluminescent peaks needs more comprehensive research using such tools as advanced EPR spectroscopy at different temperatures. At room temperature, the thermoluminescence peak at 240 °C is very resistant to fading hardly showing any loss of intensity within 24 h. The peak at 90 °C fades continuously at ambient conditions and after 24 h its intensity drops to about 10% of its original strength. Hence, this component is responsible for the hours-lasting persistent luminescence of the ScPO4:0.1%Eu3+ ceramic.

Optically stimulated luminescence of MgO:Na,Li phosphor prepared using solution combustion method

Abstract The purpose of this study is to synthesize magnesium oxide polycrystals doped with sodium and lithium (MgO:Na,Li) using Solution Combustion Synthesis (SCS) technique for developing a storage material with required Optically Stimulated Luminescence (OSL) properties. In this work, we investigated the dosimetric and luminescence characteristics of the synthesized MgO:Na,Li ceramic in pellet form. The phase identification and morphology of the samples were performed using x-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The radioluminescence (RL) emission of the obtained MgO:Na,Li pellet samples showed two different emissions bands that are dominant at ∼730 nm, and with a weak and broad emission between 300 and 590 nm. The samples characterized by a Thermoluminescence (TL) glow curve having dominant TL peaks at around 80, 155 and 315 °C at a heating rate of 5 °C/s. We carried out a step-annealing procedure to investigate the depth of the trapping centers associated with the OSL signal. The thermally affected OSL traps seems to be originated mostly from practically a single deconvoluted TL peak between 170 and 250 °C with intensity comparable to Al2O3:C when Hoya U-340 filter was used. The stability of the OSL signal was tested for shorth-term and long-term fading in dark. We determined that the total OSL area decayed around 15% after 5 weeks. We evaluated the kinetic parameters of the MgO:Na,Li using the computerized glow curve deconvolution (CGCD), Tm-Tstop method and extended initial rise method (IRM) for the TL traps, and isothermal annealing method for the OSL traps. We presented MgO:Na5%,Li5% as a workable OSL material sensitive to ionizing irradiation with suitable dosimetric properties.

Structural, optical and dosimetric characterization of CaSO4:Tb, CaSO4:Tb, Ag and CaSO4:Tb,Ag(NP)

The proposal of this work was to produce and characterize CaSO4 crystals doped with terbium and silver nanoparticles for use in thermoluminescent (TL) and optically stimulated luminescent (OSL) dosimetry. The crystalline structure, morphology and optical properties of the phosphors were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and photoluminescence. The viability of the slow evaporation route used in the production was confirmed. The silver nanoparticles (Ag(NPs)) were prepared by the method proposed by Lee and Meisel and characterized by XRD and visible absorption spectroscopy (UV–Vis). The composites were obtained from the addition of Teflon to the phosphors. Through the analyses, it was observed that the presence of silver nanoparticles slightly increases the intensity of the emission of the phosphor and shifts the dosimetric TL peak from 185 °C to 310 °C, at a heating rate of 10 °C/s. The samples presented a typical exponential OSL decay curve with a very slow component (τ3 ≥ 152 s) that indicates that the traps have a low photoionization cross-section for blue LEDs. CaSO4:Tb,Ag(NP) presented a higher sensitivity to radiation than CaSO4:Tb,Ag. The lowest detectable dose (LDD) and the fading of the TL signal of the composites were also evaluated. All samples presented a luminescent signal reproducible and linear, with TL and OSL responses proportional to the absorbed doses in the range of 169 mGy to 10 Gy.

Luminescence of impurity and intrinsic defects of Na-doped alumina ceramic

Ceramics from alumina nanopowder doped with a different Na concentration were synthesized at high-temperature sintering under vacuum and in air at a varying temperature. Pulsed cathodoluminescence spectra and thermoluminescence curves were measured to study effects based either on the formation of new defects or on the modification of alumina intrinsic defects. In fact, the emission bands with maxima of 400, 510 and 693 nm are recorded on pulsed cathodoluminescence spectra of Al2O3:Na ceramics, which are respectively responsible for their intrinsic centers of alumina (F-centers), Na and Cr impurity centers. A decrease in the synthesis temperature results in an increase in the intensity of the 510 nm band. Sodium impurity concentration growth in ceramics results in the intensity growth of the given band. It is also shown that an increase in the sintering temperature causes an increase in the intensity of all thermoluminescence peaks. Thermoluminescence curves are also changed under β-irradiation.

Thermoluminescence response of detonation diamond microparticles exposed to beta and alpha radiation

The thermoluminescence (TL) dosimetric response observed in crystalline synthetic diamondspecimens of different origin has indicated excellent levels of performance as detector and dosimeter concerning high energetic photons and particle beams. In the present work, we report on the photoluminescence and TL characteristics of detonation diamond microcrystals having 250–300 μm grain size. The high quality of detonation diamond specimens was demonstrated by photoluminescence spectroscopy with 488 nm wavelength excitation, depicting clearly the presence of negative nitrogen-vacancy [NV]− and the neutral nitrogen-vacancy [NV]o center population localized at 1.946 eV and 2.157 eV, respectively as well as a vacancy trapped at dinitrogen (2.47 eV). The TL glow curve shape, repeatability, and thermal fading were studied in samples exposed to alpha and beta irradiation. A linear dose-response was observed in the ranges of 6.6–33 Gy and 13–33 Gy, for alpha and beta irradiations, respectively. The repeatability was determined to be about 2%. The detonation microdiamonds exhibited a TL thermal fading decay of around 50% TL in a 24 h after irradiation at room temperature. A computer glow curve deconvolution was utilized by assuming four mixed order kinetics overlapped TL peaks to determine their kinetic parameters. The TL glow curve shapes and the kinetics values of the TL peaks were comparable irrespective of alpha or beta irradiated samples. The findings reflect that detonation diamond microparticles are suitable material to be used as alpha and beta radiation TL dosimeters.

Radiological emergency dosimetry – The use of luminescent mineral fillers in polymer-based fabrics

Mineral fillers are widely used in the manufacture of thermoplastics and they are commonly found in the fabrics used to form bags. We show that carbonate mineral filler grains incorporated within faux leather fabrics and the coatings applied to woven nylon fibre fabrics exhibit a bright thermoluminescence TL response to ionising radiation dose, similar to that of calcite, with a broad thermoluminescence (TL) peak at 100 °C. The fabrics tested are shown to be potentially suitable as a surrogate material for emergency dosimetry, exhibiting a linear TL response to dose between 0.1 and 10 Gy, and with a detection limit varying with fabric type from 4 to 400 mGy. The region of the TL glow curve selected for dose evaluation was between ca 100–200 °C, and this is restricted by the presence of a native signal associated with the 250 °C TL peak. The rate of fading observed varied with glow curve temperature, attributed to the presence of a distribution of trapping levels; following 24 h storage at room temperature the loss recorded for the optimal glow curve temperature region selected (160–162 °C) ranged from 30 to 80 %, according to fabric and filler type. However, the fading mechanism is predominantly thermal and its rate can be substantially reduced by storing irradiated materials below room temperature. The use of filler minerals incorporated in the manufacture of plastics provides the scope to exploit a much wider range of materials for application to emergency dosimetry.

Thermoluminescence dating of calcite – Alpha effectiveness and measurement protocols

Alpha irradiation is less efficient in inducing the thermoluminescence (TL) signal compared to beta and gamma irradiation. Although TL dating has been applied to calcite from various geological contexts, studies of the alpha effectiveness (a-values) of calcite are relatively scarce, and the reported a-values are focused on the 280 °C TL peak of speleothem calcite. In this study, three single-aliquot regenerative-dose (SAR) protocols were applied to measure the a-values of the 280 °C TL peak, the 350 °C TL peak, and the isothermal thermoluminescence at 240 °C (ITL240) of calcite from travertine, limestone and marble samples. The performances of the three SAR protocols were compared and the ITL240 signal was generally equivalent to the 280 °C TL peak TL. The a-values of the 280 °C TL peak of the samples range from 0.19 to 0.24, with a mean value of 0.20 ± 0.01, which are within the range of a-values previously reported for speleothems. The a-values of the ITL240 signal are slightly higher, and the mean value is 0.23 ± 0.01. However, the 350 °C TL peak has a lower mean a-value of 0.15 ± 0.01. The dose response curves for the 280 °C TL peak, 350 °C TL peak and ITL240 signal of the samples have characteristic saturation doses (D0) of 3000–5000 Gy, showing great potential for dating samples millions of years old.

Thermoluminescence of UV-irradiated α-Al2O3:C,Mg

The effects of ultraviolet (UV) radiation exposure on the thermoluminescence (TL) of aluminium oxide co-doped with carbon and magnesium (Al2O3:C,Mg) are reported. An Al2O3:C,Mg single crystal was investigated as a potential UV TL dosimeter after exposure to a Hg lamp radiation. The TL peak intensity and area under the curve signals were investigated as a function of the UV exposure time. Intense TL signal was obtained after UV radiation, and the area of the main TL peak at 456 K exponentially increasing with UV exposure time (within 10–120 s), with a trend for saturation for long irradiation times These results were interpreted against similar measurements using beta radiation, showing that the same defects are involved in the TL response for both types of radiation, while the different irradiation response to the two types of radiation was related to the differences in the energy dissipation characteristics, and how they affect the concentration of F-type/F-aggregate centers.

Calculated and experimental response of calcium silicate polycrystalline to high and very-high neutron doses

In the scope to the discovery of new detectors for high and very-high gamma and neutron radiation dose (mGy-MGy), synthetic polycrystals of CaSiO3 have been produced by the devitrification method in our laboratory. CaSiO3 polycrystals were irradiated with thermal, epithermal and a small fraction of fast neutrons. In the position of irradiation, the thermal neutron flux is about 83% of the total neutron flux and the thermal neutron fluences range from 5.82 × 1013 to 2.97 × 1016 n/cm2. This thermal neutron reacts with Ca, Si and O through (n,γ) process, all or part of the gamma emitted in this reaction is absorbed by the sample and is responsible for the induction of thermoluminescence (TL). The total energy emitted by the (n,γ) reaction was calculated analytically. Furthermore, Monte Carlo simulations using MCNP5 radiation transport code was carried out to calculate the deposited dose on CaSiO3 by the neutron interaction finding doses ranging from 42 Gy to 21 kGy. CaSiO3 TL glow curves, after radiation exposure from the reactor, display the main prominent TL peak around 234–259 °C and when exposed to gamma radiation (Co-60) it shows the main TL peak around same 234–272 °C.