Thermoluminescence Response Research Articles

TL response of Sm-doped MgO to 60Co gamma radiation

The thermoluminescent (TL) response of MgO doped with different rare earths was investigated. The TL material was synthesized by the solution combustion method and sintered at 1173 K; the obtained powders were prepared in pellet form. Before irradiation, the dosimeters were annealed at 623 K for 30 minutes to eliminate any TL signal generated during their manufacture. Independent tests were performed doping the MgO with Tm, Dy, Ce and Sm. The highest TL response was found for Sm-doped MgO (MgO:Sm) reaching the highest sensitivity for 0.4 mol% of Sm. For this sample, the TL response showed linearity from 0.001 to 500 Gy of 60Co gamma radiation. The lower detection limit was found to be equal to 1.17 μGy. The sensitivity of the MgO:Sm prepared dosimeter was approximately 10% the sensitivity of the commercial TLD-100. The TL signal fading was found to be 6% after one month. The deconvolution of the glow curve showed a symmetric peak with a general order kinetics, b, centered at 474 K. These results suggest that this new TL material could be a promising detector to use in diverse dosimetry applications.

Thermoluminescence response of Ce doped CaTiO3 nanophosphor synthesized by hydrothermal method for gamma dosimetry

Abstract Nanocrystalline calcium titanate (CaTiO3) doped with cerium ions (0.02 mol%) was synthesized via hydrothermal method and its luminescent properties were studied for gamma dosimetry. For the synthesized samples, the best luminescent response was achieved after annealing at 700 °C for 8 h. The synthesis was confirmed via XRD technique yielding the cyrstallite size of 22 nm for the most intense peak (121). The surface morphology was studied via scanning electron microscopy (SEM) yielding the grain size of 12 µm. The strong IR absorptions appeared at 700 cm−1 and 712 cm−1 attributed to bending mode of vibrations changing angle between Ti–O–Ti for CaTiO3 and CaTiO3:Ce respectively, as confirmed via Fourier-Transform Infrared (FTIR) Spectroscopy. Thermoluminescent (TL) response of undoped and doped samples was studied by Mikrolab RA94 TLD Reader-Analyzer having heating rate 10 °C/s, for absorbed doses 0–20 mGy from 137Cs γ-source having a dose rate 100 mSv/h. The found values at 662 keV for the photon-sensing parameters, i.e., mass attenuation coefficients (μ/ρ), mass-energy attenuation coefficient (μ en/ρ), effective atomic number for photon interaction (Z eff,PI) and effective atomic number for total photon energy absorption (Z eff,PEA) were 0.07030882 cm2/g, 0.0280245 cm2/g, 13.9 and 13.4 respectively. Thus, synthesized nanophosphor has shown excellent thermoluminescent dosimetric response for gamma radiation sensing in the selected dose range.

Studying the structure, photoluminescence and thermoluminescence properties of LiCaBO3 pseudoternary glass-ceramic co-doped with Ce3+, Sm3+ ions

The lithium-calcium-borate (LiCaBO3) glass co-doped with Ce3+ and Sm3+ ions were successfully fabricated by the conventional melt quenching method. Annealing heat at 710 °C for 2 or 4 h formed the nanocrystals in the glass matrix. The X-ray diffraction patterns have proved the formation of the nanocrystals in materials. The appearance of these nanocrystals changed the glass lattice structure as well as the physical and optical properties of the material. The radiative properties of the LiCaBO3 glass and glass ceramics were analyzed within the framework of Judd-Ofelt theory. The thermoluminescence (TL) properties of the materials were studied by analyzing the glow curve and the TL spectra. The application potential of the materials in the field of dosimetry was proposed based on the investigation results of the parameters such as TL response to irradiation dose, fading rates, and the standard deviation.

TL, EPR, and optical properties of undoped and Eu-, Ce-, Tb-, Sm-, Cu-, Mn-, and Li- doped MgSiO3 phosphors, synthesized by sol-gel combustion technique

Polycrystalline MgSiO3 samples, undoped or doped with rare earth- (Eu, Tb, Ce, Li, Sm), transition- (Mn and Cu), and alkali metal- (Li) elements, were prepared by the sol-gel combustion method and characterized by thermoluminescence, electron spin resonance, and optical properties. Enstatite and protoenstatite phases are observed in undoped and doped MgSiO3. Better TL results have been observed for phosphors doped with Tb, Ce, and Li (0.5 % mol). Fading experiments and the GCD method have been performed. EPR signals of gamma-irradiated phosphors indicate the formation of radiation-induced defect centers. Cu-doped MgSiO3 shows an unusual feature of the Cu2+ ion. The Cu2+ ion occupies a tetragonally compressed octahedral site, presenting an unconventional attribute. Optical bandgap value Eg is higher for the Ce, Tb, Mn, Li, Sm, and Cu-doped MgSiO3 phosphors. Ce, Li, and Tb dopant ions were found suitable for the MgSiO3 sample regarding its thermoluminescent response and its possible application in radiation dosimetry.

SrAl2O4: Ce: Synthesis and dosimetric characteristics of a new highly sensitive TL phosphor for dosimetry

Strontium aluminate (SrAl2O4) doped with different Ce concentrations was synthesized by the solid-state reaction method to find the best thermoluminescent response. The crystal structure of the material has been analyzed by Rietveld refinement of X-ray diffraction (XRD) results. The effects of different dopant concentrations and thermal annealing regimes on TL sensitivity and the optimum conditions for producing dosimeters with superior sensitivity to commercial dosimeters were investigated. It has been shown that the maximum TL sensitivity is obtained at a concentration of 0.3 mol% Ce and a heat treatment at 1000 °C for 2 h. The TL glow curve of Ce-doped strontium aluminate (SrAl2O4) pellets shows three TL peaks at 90, 150, and 250 °C. The dosimetric characteristics of the new material examined in this work are linear response in the dose range with applications in personal and environmental dosimetry; TL sensitivity; minimum detection dose; reproducibility; energy dependence; and TL signal fading. Based on the results obtained, the synthesized material is a dosimeter with a sensitivity 2.44 times higher than the commercial dosimeter TLD-100 (LiF:Ti,Mg).

Thermoluminescence response of carbon ion beam irradiated LiCaAlF6: Tb phosphor

Accurate measurement of the dose delivered to patients is crucial in any radiation therapy, including C ion beam radiotherapy, to ensure effective treatment and minimize the risk of damage to healthy tissues. The accessibility of thermoluminescence (TL) - based materials for carbon ion beam dosimetry continues to be constrained. With the aim of this, an investigation has been done to study the TL properties of the Terbium (Tb) doped LiCaAlF6 phosphor following irradiation with C ion beam. The LiCaAlF6: Tb phosphor has been synthesized using melting method in argon gas atmosphere. TL glow curves has been analyzed on exposure to carbon ion beams at energies of 85 MeV and 50 MeV within the fluence range of 109 - 1012 ions/cm2. The TRIM code, relying on Monte Carlo simulation, has been employed to compute parameters such as absorbed dose, ion range, and energy loss. The Tb-doped LiCaAlF6 phosphor exhibits a glow curve structure with distinctly resolved peaks at 130 °C and 325 °C. Notably, the TL intensity has been significantly increased by 105 times than that of undoped LiCaAlF6. This enhancement is attributed to the generation of a high density of Tb-associated defects within the energy band gap. The TL enhancement has been elucidated based on charge compensation mechanism. Further, TL glow curve shape and structure remain consistent across different energies, i.e., 85 and 50 MeV C ion beams, indicating an energy-independent behavior of this phosphor. Nevertheless, the TL intensity at 85 MeV is higher compared to that at 50 MeV. Detailed dosimetry properties have been investigated for 85 MeV C ion beams within the fluence range 2x109-5x1012 ions/cm2. The phosphor exhibits a sublinear dependence against dose for the studied fluence range with no discernible shift in peak position. The favorable outcomes include low fading during the initial days of storage time and batch homogeneity. TL glow curve analysis indicate the formation of trapping level in the range of 0.90–1.72eV within the band gap of the phosphor which are responsible for TL process. The phosphor's simple glow curve structure, minimal fading, consistent batch homogeneity and high stability of the glow curve suggest that the material can be explored for C ion beam dosimetry application.

Effect of the Crystalline Phase Type on the Thermoluminescent Response of ZrO2 Due to Different Synthesis Methods

ZrO2 samples were obtained using three different synthesis methods (Calcination, Co-precipitation and Hydrothermal). The samples were characterized to analyze the effect of the crystalline phase on their thermoluminescent (TL) and photoluminescent (PL) responses. The ZrO2 phase was analyzed by X-Ray diffraction (XRD) and Raman. Nanoparticle size distribution was obtained by scanning electron microscopy (SEM). For optical analysis, characterizations included absorbance measurements, where samples exhibited modifications in color centers, PL emission and experimental fluorescence lifetime decay ([Formula: see text] measurements. Additionally, their TL response was studied under UV (245[Formula: see text]nm and 385[Formula: see text]nm), and 6[Formula: see text]MV photon energy from LINAC excitation. The obtained results show the improvement of TL and PL properties due to ZrO2 phase while an amorphous ZrO2 synthesized by hydrothermal method is an excellent prospect to be used as TL material and it may be a promising scintillator material at 254[Formula: see text]nm.

Graphite foils as potential skin and epithelium dosimeters at therapeutic photon energies

This work builds upon a prior study, examining the dosimetric utility of pencil lead and thin graphitic sheets, focusing upon the measurement of skin doses within the mammographic regime. In recognizing the near soft-tissue equivalence of graphite and the earlier-observed favourable thermoluminescence yield of thin sheets of graphite, this has led to present study of 50 μm thick graphite for parameters typical of external beam fractionated radiotherapy and skin dose evaluations. The graphite layers were annealed and then stacked to form an assembly of 0.5 mm nominal thickness. Using a 6 MV photon beam and delivering doses from 2- to 60 Gy, irradiations were conducted, the assembly first forming a superficial layer to a solid water phantom and subsequently underlying a 1.5 cm bolus, seeking to circumvent the build-up to electronic equilibrium for skin treatments. Investigations were made of several dosimetric properties arising from the thermoluminescence yield of the 50 μm thick graphite slabs, in particular proportionality and sensitivity to dose. The results show excellent sensitivity within the dose range of interest, the thermoluminescence response varying with increasing depth through the stacked graphite layers, obtaining a coefficient of determination of 90%. Acknowledging there to be considerable challenge in accurately matching skin thickness with dose, the graphite sheets have nevertheless shown considerable promise as dosimeters of skin, sensitive in determination of dose from the surface of the graphite through to sub-dermal depth thicknesses.

Luminescent properties and dosimetric behavior of Eu-ion-doped ASO4 (A = Ca, Sr, and Ba)

We investigated the luminescence properties and dosimetric behavior of Eu-ion-doped ASO4 (A = Ca, Sr, or Ba) phosphors synthesized using the coprecipitation method. Structural analysis of the phosphors was performed using X-ray diffraction patterns, which revealed that the prepared samples exhibited a pure phase with diffraction peaks matching those of undoped orthorhombic structures. The luminescence properties of the phosphors were examined by measuring photoluminescence and photoluminescence excitation spectra. We found that both Eu2+ and Eu3+ emissions were detected for A = Ba and Ca, whereas only Eu2+ emission was observed for A = Sr. Further, time-resolved photoluminescence decay curves indicate the presence of Eu2+ and Eu3+ luminescence with different lifetimes. The optically stimulated luminescence (OSL) and thermoluminescence (TL) responses of the samples were investigated. The OSL and TL responses were found to vary linearly with the irradiation dose. This study sheds light on the potential applications of Eu-ion-doped ASO4 phosphors in radiation dosimetry and optoelectronic devices.

Usability of sand samples in TL Radiation Dosimetry.

This study investigated natural sand thermoluminescence (TL) response as a possible option for retrospective high-dose gamma dosimetry. The natural sand under investigation was collected from six locations with selection criteria for sampling sites covering the highest probability of exposure to unexpected radiation on the Egyptian coast. Dose-response, glow curve, chemical composition, linearity, and fading rate for different sand samples were studied. Energy Dispersive X-ray Spectroscopy (EDX) analysis revealed differences in chemical composition among the various geological sites, leading to variations in TL glow curve intensity. Sand samples collected from Ras Sedr, Taba, Suez, and Enshas showed similar TL patterns, although with different TL intensities. Beach sands of Matrouh and North Coastal with a high calcite content did not show a clear linear response to the TL technique, in the dose range of 10Gy up to 30kGy. The results show that most sand samples are suitable as a radiation dosimeter at accidental levels of exposure. It is proposed here that for high-dose gamma dosimetry with doses ranging from 3 to 10kGy, a single calibration factor might be enough for TL measurements using sand samples. However, proper calibration might allow dose assessment for doses even up to 30kGy. Most of the investigated sand samples had nearly stable fading rates after seven days of storage. The Ras Sedr sands sample was the most reliable for retrospective dose reconstruction.

Exploring beta irradiation responses in Sr2+-Doped hydroxyapatite: A thermoluminescence study

This research investigates the structural and thermoluminescence (TL) properties of Sr2+-doped Ca5(PO4)3OH (HAp) phosphors. X-ray diffraction (XRD) analysis confirms that HAp has a hexagonal structure with a P63/m space group. The TL behaviour of HAp:Sr2+ phosphors is examined under beta irradiation in the temperature range of 25–500 °C. The study reveals three TL glow peaks at temperatures of 75, 212, and 296 °C. Investigation of TL responses across heating rates (HR) ranging from 0.1 to 5 °C/s shows that higher HRs result in increased maximum TL peak temperatures and reduced TL intensities. This trend suggests an augmented contribution from non-radiative transitions as the heating rate increases. Importantly, no evidence of thermal quenching is found in the HAp samples. Two different methods, Hoogenstraaten's and Booth-Bohun-Porfianovitch, yield consistent activation energy values of 0.50, 1.22, 1.67 eV, and 0.48, 1.19, 1.63 eV, respectively. Reusability assessments indicate a standard deviation of less than 5 %, confirming the reliability of the materials. Tm−Tstop analysis reveals a continuous distribution of trap levels. TL properties in HAp samples have been comprehensively characterized, contributing not only to enhancing our understanding of their behaviour, but also highlighting their potential applications in various areas. The findings of this study have provided valuable insight into the development of efficient catalysts that are suitable for a variety of applications.

Correlations between quartz OSL dose-response curve and TL glow curve characteristics, and their implications for equivalent dose estimation

Optically stimulated luminescence (OSL) dating of quartz using the single-aliquot regenerative-dose (SAR) procedure requires construction of dose-response curves (DRCs). The shapes of DRCs and their characteristic saturation doses (D0 values) are well-known to be highly variable between samples and among individual grains from the same sample, but the factors that control DRC characteristics are imperfectly understood. Here we report correlations between OSL DRC shapes and thermoluminescence (TL) glow curve characteristics for a sample of quartz from northern Australia. Individual grains were measured using the SAR procedure and one of two preheat temperatures (160 °C and 260 °C), and grouped according to similarities in their DRC shapes. Grains from each DRC group were then physically transferred onto a separate disc for TL measurement as a multi-grain aliquot. A strong correlation was observed between DRC group and laboratory-irradiated TL glow curve shapes, along with some differences between the two preheats. Irrespective of the selected preheat, earlier saturating DRC groups are associated with the most intense 110 °C TL signal, and the least intense 325 °C TL signal, which corresponds to the main OSL trap. Later saturating DRC groups generally show the opposite trend. There are also trends within other regions of the glow curve and DRC group, such as prominent TL responses at 140–160 °C, 220–240 °C and 390–410 °C. We assessed the effect on the accuracy of equivalent dose (De) estimation using an associated radiocarbon age as an independent cross-check of the OSL ages for the DRC groups. De over- and under-estimates were obtained for some DRC groups. Most notably, grains preheated to 160 °C displayed a pattern of De values which decreased with an increase in D0. We relate this to variable concentrations of charge at the ∼230 °C TL trap prior to regenerative dose OSL measurements. OSL ages for most DRC groups preheated to 260 °C are close to the radiocarbon age, as are those of later saturating DRC groups preheated to 160 °C; the latter DRC groups have the smallest TL signals at ∼230 °C relative to the TL peak at 325 °C. The results of this study suggest that correlations between single-grain De and D0 values can occur due to underlying differences in the TL characteristics of grains with different DRC shapes. In the absence of independent age control and prior to measuring multi-grain aliquots of quartz, we recommend that OSL dating practitioners screen their samples for any single-grain patterns of De as a function of DRC shape, to determine the optimal SAR measurement conditions and data-analysis procedures for De estimation.

Thermoluminescence dosimetric characteristics and glow curve analysis of Eocene rock salt, the gray halite, mined from Bahadur Khel site, Pakistan

Thermoluminescence (TL) response of naturally occurring Eocene rock salt (Gray halite) is assessed for its potential use as a cost-effective phosphor for dosimetric applications. Natural deposits of the Eocene salt lie on the Himalayan foothills in Pakistan. The grayish color of the halite is due to the intermixing of black bitumen/shale. EDS and ICP-OES techniques are used for the analytical study of the sample. It confirms the presence of Ca, K, Mg, Sr, Zn SO4, Mn, Al, Si and Fe along with the main matrix-NaCl. The Eocene salt is sulfur (S) rich, and potassium (K) poor mineral as compared to the other regional halite. The XRD analysis shows that lattice structure of the halite is composed of two interpenetrating FCC-sublattices of Na and Cl. Cold pressed pellets weighing 40 mg are produced for dosimetric study of the material. Standard gamma source is used for pellet irradiaition. Three different samples of Eocene salt (i.e. rock salt, naturally precipitated salt and refined salt) are prepared. It is observed that, if the material is used as such in its natural form, the dosimetric peak of the glow curve occurs at higher temperature >260 °C. The raw form of rock salt is therefore pre-processed (refined) whereby the major glow peak has shifted onto the dosimetrically significant position at 230 °C. Because of the optimal shape of the glow curve, the refined salt sample is investigated in detail: TL glow curves are acquired from 50 °C to 300 °C, the phosphor reveals a composite glow curve where four peaks are observed at approximate positions of 110 °C (P1), 145 °C (P2), 180 °C (P3) & 230 °C (P4). TL response is studied in the range of 5 mGy to 2 Gy; where a linear/superalinear dose-response behavior is observed for the current material. The Minimum Detectable Dose Limit (MDDL) is measured from the linear region and found to be 0.37 mGy. The first readout results in very low residues <0.005 % and is sufficient to afresh the dosimeter for the next reading. A repeatability test is performed up to 20 identical cycles: the resultant COV, obtained for refined salt sample, is 2.3 % (and 1.5 % in 10 cycles). The irradiated pellets show about 20 % loss of the initial signal for one month fading study. Tm-Tstop method and CGCD techniques are used for kinetic analysis. Kinetic parameters (b, E and s) are estimated from multiple glow curves and found similarities in the results. The results of the preliminary investigations suggest that the pellet prepared from Eocene salt has a potential for use in TL dosimetry.

Structural and thermoluminescence properties of lithium borate glass matrices under UV and beta radiation.

In the present work, glass samples in the (100 - x)B2O3-xLi2O binary system, with x varying from 30 to 50 mol%, were prepared using the conventional melting and moulding method, with the main objective of evaluating the thermoluminescence response when exposing these materials to ultraviolet (UV) radiation. Complementary analysis based on density, optical absorption on the UV-visible region (UV-vis absorbance), Fourier transform infrared spectroscopy on the medium region, X-ray diffraction, and differential thermal analysis measurements were performed. Thermoluminescence measurements of vitreous samples showed glow curves with at least one peak with a maximum temperature of ~170°C after exposure to UV radiation in the temperature range 50-250°C. Samples were also exposed to beta radiation in the temperature range 25-275°C, also showing single peaks with a maximum temperature of ~150°C.

Evaluation of TL and OSL signals of MgB4O7:Tm,Li prepared by the solution combustion method

Magnesium tetraborate (MgB4O7) doped with rare-earth elements is recognized for its suitability in thermoluminescence (TL) dosimetry due to its low effective atomic number (Zeff = 8.4) and the potential applications in neutron dosimetry. The study investigates the luminescent (TL and OSL) properties of MgB4O7 doped with thulium (Tm3+) and lithium (Li+). Samples were synthesized using the solution combustion method and TL and OSL responses were evaluated using a spectrometer and an automated OSL/TL reader. The emission lines of Tm3+ are consistent with previous literature, with Li+ enhancing TL and OSL responses. TL emission spectra unveil distinct bands corresponding to [Tm3+]* transitions. The electron paramagnetic resonance (EPR) spectroscopy analysis carried out in unirradiated, irradiated and annealed samples.The results show that the signals corresponding to BO32− and O2− are seen upon irradiation and disappear after annealing at 200 °C, indicating the participation of these centers in the TL process. The results show that the TL response of MgB4O7:Tm,Li is much more sensitive to gamma radiation than MgB4O7:Tm, with a minimum detectable value of 0.084 mGy and a linear response with dose for the range studied, from 0 to 500 mGy, with R2 of 0.998.

Thermoluminescence (TL) and electron paramagnetic resonance (EPR) of dumortierite sensitized by heat treatments

The present study presents the effect of heat treatment on TL and EPR of dumortierite. It was found that applying a heat treatment at 1200 °C for 1h, followed by slow cooling to room temperature, is optimal for improving its TL sensitivity. The glow curves of the sensitized dumortierite sample show TL emission bands centered at 350, 475, and 580 nm. The kinetic parameters of the TL peaks were obtained using the Tm-Tstop and deconvolution methods. In addition, sensitized dumortierite exhibits a linear response with γ-radiation dose and low fading in its TL response. Studies using the technique of EPR were carried out to investigate the defect center EPR signals observed after γ-irradiation. A single defect center with an axially symmetric g-tensor was observed with principal values g∥ = 2.0009 and g⊥ = 2.0017. The center was attributed to an F+ center and appears to correlate with the TL peak at 200 °C.

Influence of the synthesis pathway upon the thermoluminescent response of gadolinium aluminate matrix phosphors

The phosphors endowed with a glow curve have a peak much more intense than the others, sensitization to low doses, and a linear relationship between the thermoluminescent response and the dose, which are in demand in the dosimetry market. The gadolinium aluminate has been successfully used as a host lattice of phosphors with luminescent properties. Principally, the luminescent response of the said matrix has been improved by doping with rare earth ions. The thermoluminescent signal depends on the synthesis route because the defect density of a crystal is closely connected to the production pathway that the material went through. Therefore, a crucial step in sensitizing a phosphor is selecting a synthesis route that enhances the efficiency of its thermoluminescent mechanisms. The research herein focused on synthesizing phosphors composed of gadolinium aluminate with no dopant and doped with two molar percent of dysprosium, using two different routes. Among the two synthesis pathways, it was determined to be the most suitable for enhancing the thermoluminescent response of the aforementioned phosphors. The methods employed were reverse coprecipitation and the modified citrate precursor. The phosphors obtained by the reverse coprecipitation method showed the most sensitive thermoluminescent signal. Mainly, the phosphor activated with the dysprosium ion produced the most intense signal, suggesting an improvement in the thermoluminescent mechanisms due to the dopant insertion.

Synthesis and thermoluminescence characteristics of beta irradiated nanocrystalline calcium aluminate doped with lanthanum oxides

This study investigated the thermoluminescence (TL) characteristics of calcium, a nano-phosphor doped with a rare earth element (lanthanum, La). Six different concentrations of dopants were prepared by the sol-gel method. The XRD data displayed that the particle size was 52.48 nm. The surface morphology was examined by SEM analysis. The highest TL response of the nano-phosphor CaAl2O4 was found with a dopant of 0.1 % La, which has the most intense TL peak. The Computerized Glow Curve Deconvolution (CGCD) and Variable Heating Rate (VHR) methods were carried out for trap-level analyses and activation energy determination. The deconvolution of the glow curves displayed thirteen superimposed TL glow peaks located between 362 and 717 K. The TL response of CaAl2O4:0.1 % La nano-phosphor showed linearity in the beta dose range from 2.2 Gy up to 330 Gy for all the deconvoluted glow peaks. The minimum detectable dose of the prepared samples is 284 μGy. Other parameters, such as the sensitivity and reproducibility of the prepared samples, were determined. It is concluded that CaAl2O4 with a dopant of 0.1 % La is a good material for dosimetry applications.

Thermoluminescent composites of sintered synthetic-topaz/in situ corundum for dosimetry by a novel reversible process

Topaz (Al2F1·44(OH)0·56SiO4)/corundum (Al2O3) composites were prepared by a facile and novel reversible process from the sintering of synthetic topaz and AlF3 powders, with corundum formed in situ into the topaz matrix. The corundum formation reaction occurs in the temperature range 875–975 °C, from 40 min sintering time, obtaining the topaz- Al2F1·44(OH)0·56SiO4/corundum- Al2O3 composites. Although sintering temperature and time increment lead to higher corundum formation in the topaz matrix (78.4 wt % Al2O3 at 975 °C for 60 min), longer residence times give place to corundum percentage decrease due to topaz reconversion. The composites' microstructure is characterized by a rectangular bar with stacked pyramidal ends and polycrystals of hexagonal plates for topaz and corundum, respectively. For the topaz/corundum composites, the maximum density was 3.05 g/cm3 (17 % porosity) for specimens sintered at 925 °C for 20 min. The glow curves of the topaz/in situ corundum composite sintered at 975 °C and 0 min dwell time show thermoluminescent peaks between 180 and 250 °C, useful for dosimetric applications. The most helpful peak (at 221 °C) in the topaz/corundum composite's glow curves determined by computational deconvolution is sharp and exhibits the highest thermoluminescent response. Dose-response analysis of the composite (sintered at 975 °C for 0 min) with the best thermoluminescent response revealed two ranges of linear behavior, the first from 2 to 200 mGy, with an adjustment of 99.9 % and the second in the range 5–300 Gy (99.8 % fitting). The thermoluminescent response improvement of the topaz/corundum composites is attributed to the corundum formed in situ during sintering. Fading rate studies of the composite with the best sintering treatment revealed a signal decrease of 4 % after 15 days, which remained constant for up to 30 days, and 8 % after 60 days. The kinetic parameters, kinetics order (b), activation energy (E), and frequency factor (s) determined using the glow peak shape method showed second-order kinetics. The topaz/corundum composite with the best TL response (975 °C, 0 min) presents an effective atomic number (Zeff) of 11.74. The detection of lower doses (mGy) and the linear response at higher doses (Gy) of beta 90Sr, together with the other thermoluminescent properties, suggest that the topaz/corundum composites sintered at 975° for 0 min dwell time may find application in radiotherapy, geological dating, and environmental dosimetry.

Synthesis, thermoluminescence characterizations, and photon attenuation parameters of MgAl2 O4 structure doped with different ions.

In this work, different ion co-doped Mg1-x Al2 O4 nanophosphors, coded as M5Cr-5La A, M5Cr-5Cu A, M0.07Si-0.03Ce A, and M0.05Ti-0.05La A, where 5Cr-5La, 5Cr-5Cu, 0.07Si-0.03Ce, and 0.05Ti-0.05La representing the added ions (mol%), were prepared using the sol-gel method. Phase structure, transmission electron microscope (TEM) images, and element feasibility were checked using X-ray diffraction, TEM analysis, and energy dispersive X-ray (EDX) spectroscopy. Their thermoluminescence (TL) response was checked using a 5Gy γ-test dose. The M0.05Ti-0.05La A sample was found to be best for the TL response with an ~1.1 times response compared with that of the MTS-700 commercial detector. A wide range of dose-responses for the M0.05Ti-0.05La A sample was found up to a 20 Gy γ-dose with the lowest detectable dose of ⁓23 μGy. Photon attenuation parameter results were Zeff ⁓10, which mean that the M0.05Ti-0.05La A sample could be considered as a near tissue equivalent material. Due to this study, the M0.05Ti-0.05La A sample can be considered as a promising detector for application in personal and medical dosimetric monitoring.