Thermoluminescence Spectroscopy Research Articles

A custom-made integrated system for thermoluminescence and radioluminescence spectroscopy

Thermoluminescence (TL) and Radioluminescence (RL) are widely used in dosimetry applications. We present a custom-built integrated system, designated LUMI22, for measuring TL, TL spectroscopy, RL, and RL as a function of temperature. LUMI22 includes a heating system based on Kanthal® A1 alloy (FeCrAl), a microcontroller to regulate the temperature ramps (e.g. 1–5 °C/s). To irradiate samples an X-ray tube (Moxtek 50 kV, 50 μA) is powered, controlled, and monitored by an FTC-200 standard controller. The dose rate at the sample position is 0.43 Gy/min. Light collection includes a Photomultiplier Tube (PMT, Hamamatsu H10493-012:HA, 185–850 nm). Additionally, a miniature fiber optic spectrometer (Ocean Optics, QE65000, range 200–1100 nm) coupled with a 1000 μm diameter fiber optic (QP1000- 2-UV-VIS) was employed for TL and RL spectroscopy measurements. To assess the functionality of the system, it was used to measure TL and RL from Al2O3:C,Mg, Al2O3:C and TLD-100 phosphors which have been previously well investigated. The measured TL and RL data were well compared to the published ones, confirming the functionality of the system.

Preparation and Luminescence Properties of Broadband Orange-Emitting Persistent ScBaZn3GaO7:Bi3+ Phosphor.

This article describes a new kind of afterglow material, ScBaZn3GaO7:Bi3+, which was synthesized through a high-temperature solid-phase method. Its crystal structure, photoluminescent characteristics, and afterglow characteristics were studied and analyzed. Upon excitation at 344 nm, ScBaZn3GaO7:Bi3+ exhibits broadband emission with a central wavelength located at 571 nm (fwhm = 172.98 nm). The sample exhibits an internal quantum efficiency of 65.1%. The bright yellow persistent luminescence of the ScBaZn3GaO7:Bi3+ sample was observed after 365 nm irradiation. Thermoluminescence spectroscopy revealed four primary traps within ScBaZn3GaO7:Bi3+, with depths of 0.676, 0.794, 0.882, and 0.972 eV. The traps located at energy levels of 0.676 and 0.794 eV were identified as the key contributors to the sample's afterglow. Finally, the ScBaZn3GaO7:Bi3+ sample was combined with a UV-LED chip to fabricate a high-power warm white-light-emitting diode (WLED) device, indicating the potential application prospect of ScBaZn3GaO7:Bi3+ phosphor in single-phase warm WLEDs.

Defect modulation and color tuning of MgO: Probing the influence of Sm and Li dopants through x-ray absorption, photoluminescence, and thermoluminescence spectroscopy

Pure, singly doped (Sm), and co-doped (Sm, Li) MgO nanoparticles have been prepared using the solution combustion method. X-ray diffraction (XRD) analysis has revealed the development of microstrain, alteration in the unit-cell parameters, and dislocation/defect densities in the MgO lattice as a function of Sm and Sm+Li doping. Transmission electron microscopy (TEM) images and selected area electron diffraction (SAED) patterns illustrate the formation of polycrystalline samples ranging from 45 nm to 65 nm in size. X-ray absorption near-edge structure (XANES) spectroscopy at Sm L-edge confirms the presence of the +3 valance state of Sm dopants. Mg K-edge XANES features convey the lesser coordination of Mg2+ ions upon increasing the Sm3+ ions. O K-edge XANES convey the formation of O2- vacancies or F centers upon Sm3+ doping. Two excitation wavelengths, λexcitation = 275 nm, and λexcitation = 405 nm, have shown significant emission at blue and yellow-red regions, respectively. Additionally, utilizing XANES as a methodological tool for examining defects and incorporating PL and TL findings provides a comprehensive understanding that is relatively infrequent in previous research. Thermoluminescence (TL) studies, conducted over a temperature range of 340 K to 675 K with three irradiation doses of γ-rays (100 Gy, 500 Gy, and 1000 Gy) are convincing the formation of multiple levels of radiative traps, enhancing peak intensity at 437 K and radiation doses independent of peak intensity at 437 K.

Investigations of structural, photoluminescence, colorimetric, lifetime, and luminous efficiency of Tb3+ and Sm3+ co-doped calcium tungstate for WLEDs

Structure, photoluminescence, colorimetric, and thermoluminescence analysis of Ca1-x-yTb2x/3Sm2y/3WO4; x = 0.01; y = 0.01–0.05 ceramics are reported in this manuscript. The materials are made by the use of the solid-state method. Reitveld refinements of the obtained X-ray diffraction patterns are done by using the Fullprof Suite software. The obtained results denoted that the synthesized materials have a tetragonal structure and I41/a space group. Energy bandgaps are found in the UV–visible absorbance spectra. Photoluminescence investigations of the phosphors are done. The critical quenching concentrations of the phosphor are found to be x = 0.01; and y = 0.04. Moreover, the critical distance of energy shift with the adjacently presented ions is computed. Dexter’s theory is employed to elucidate that the dipole-dipole electronic interactions are the imperative reasons for the transfer of energy in the phosphor. The white color of emission is achieved for x = 0.01, y = 0.04 Tb, and Sm doped CaWO4 material. Moreover, great values in color purity, correlated color temperature, color rendering index as well as luminous efficiency of radiation are obtained from the CIE Chromaticity coordinates. Quantum yield efficiency of x = 0.01, y = 0.04 Tb & Sm codoped CaWO4 is measured. Photoluminescence decay analysis of all the samples is done to study the long-after glow properties and also the average lifetime values are evaluated. This is an indication of the suitable usage of the prepared materials in the white light-emitting diodes. Concentration as well as dose-dependent Thermoluminescence spectroscopy is investigated thoroughly. Kinetic parameters are calculated by deconvoluting the spectra of x = 0.01; y = 0.01 Tb & Sm codoped CaWO4 irradiated with 15 min of UV excitation dose. These results are denoted by high trap depth, second-order kinetics, and low UV dosimetry of the phosphor.

Inorganic metal oxide material BaSiO3:Eu2+ for convenient 3D X-ray imaging

X-ray storage phosphors are found wide-ranging applications in medical diagnosis, nondestructive testing and X-ray imaging. However, designing X-ray storage phosphors with high electron storage capacity still poses a daunting challenge. In this study, we designed a fluorescent powder based on Eu2+-doped BaSiO3, demonstrating excellent optical information storage characteristic. Under high-energy X-ray filling, shallow traps exhibit low electron capacity and only produce weak afterglow, which greatly helps to minimize the impact of afterglow on the image quality during X-ray imaging. In addition, the deep traps at 1.01 eV filled with high-energy X-ray allow the material to store information for a long time. The crystal structure, photoluminescence (PL) and thermoluminescence (TL) spectra were studied systematically. The electron trapping properties of the material were analyzed using TL spectroscopy. Finally, we fabricated a flexible film with phosphors, the flexible film has been utilized to demonstrate high-quality real-time X-ray imaging and achieve time-delayed X-ray imaging of curved objects, such as flexible circuit boards.

Broadband near-infrared (NIR) emitting Cr3+ -doped La3 Ga5 SnO14 phosphor with long persistent and photostimulated persistent luminescence.

Recently, long persistent phosphors (LPPs) have attracted significant attention as promising candidates for biomedical applications. However, the serious decrease in luminescence intensity in tissue still remains a major challenge. Therefore, exploring more competitive LPPs and achieving reproducible tissue imaging is crucial. In this study, a new series of near-infrared (NIR) phosphors La3 Ga5 Sn1-x O14 :xCr3+ (x = 0.005-0.05) were synthesized using a high-temperature solid-state method. The as-synthesized samples were characterized using X-ray diffraction, diffuse/photoluminescence spectroscopy, fluorescence decay curves, and thermoluminescence spectroscopy. Upon excitation with ultraviolet light, strong emission bands were observed in the range 600-1200 nm with an optimal doping concentration of x = 0.02mol. Moreover, La3 Ga5 SnO14 :Cr3+ exhibits persistent luminescence due to the presence of suitable energy traps, which prompted the phosphor to emit NIR light even after the removal of the excitation source.

Experimental and Computational Study of Elasticoluminescence in Gd2O2S:Tb3+: Implications for Mechanoluminescence Origins

Mechanoluminescent materials can convert mechanical stress into light. Among these, elasticoluminescent materials are useful for monitoring periodic and repetitive events. However, the development of high-performance elasticoluminescent materials remains a significant challenge because of the lack of understanding of the structures and mechanisms underlying mechanoluminescent materials. To address this issue, this study investigated the elasticoluminescence properties of Gd2O2S:Tb3+ through a comprehensive analysis using experimental and computational techniques. Using thermoluminescence spectroscopy and density functional theory, we observed that trap states within the bandgap are generated by the O2− and S2− anion vacancies, which contribute to mechanoluminescence. The observation of green mechanoluminescence (ML) characteristics in Gd2O2S:Tb3+ was accompanied by a meticulous analysis of their origins, which aligned significantly well with the computational results. These findings enhance our understanding of the origin of ML and provide a solid foundation for the development of next-generation high-performance ML materials, thus fostering advancements in various fields of advanced technology research.

Exploration of crystal structure, and luminescence behaviors of Terbium-activated CaWO4 phosphor

This manuscript includes structural, optical, photoluminescence, and thermoluminescence behaviors of Terbium incorporated CaWO4 samples with nominal compositions of Ca1-xTb2x/3WO4 (x = 0.01, 0.02, 0.03, 0.04, 0.05) prepared by the traditional solid-state reaction route. Results found from the Rietveld refinements of X-ray diffraction patterns confirmed that all the samples have tetragonal crystal structures with I41/a space group. The variation of unit cell volume with the compositions shows an anomaly at x = 0.03. Band gap energy values of these synthesized samples are found from the UV–Visible absorbance spectra with increasing order. Photoluminescence behaviors, as well as the FWHM values, are analyzed from the excitation along with the emission spectra. Critical quenching concentration at x = 0.03 with a critical energy transfer distance of ∼ 20 Å caused by the dipole-dipole interactions is found in these spectra. CIE Chromaticity coordinates are indicated the green emission color of all the prepared samples with high color purity, correlated color temperature, color rendering index, and luminous efficiency of radiation values. Quantum efficiency of the material with x = 0.03 Tb concentration is observed under 255 nm excitation wavelength. PL decay analyses of the phosphors are carried out and the average lifetime values are calculated. Thermoluminescence spectroscopy of x = 0.03 irradiating by 15 min of UV dose is described as the lower UV dosimetry and second-order kinetics of the material.

Radiation and Emission Phenomena in Combination

Radiation and Emission Phenomena in Combination

Addressing Current Challenges in OSL Dosimetry Using MgB4O7:Ce,Li: State of the Art, Limitations and Avenues of Research.

The objective of this work is to review and assess the potential of MgB4O7:Ce,Li to fill in the gaps where the need for a new material for optically stimulated luminescence (OSL) dosimetry has been identified. We offer a critical assessment of the operational properties of MgB4O7:Ce,Li for OSL dosimetry, as reviewed in the literature and complemented by measurements of thermoluminescence spectroscopy, sensitivity, thermal stability, lifetime of the luminescence emission, dose response at high doses (>1000 Gy), fading and bleachability. Overall, compared with Al2O3:C, for example, MgB4O7:Ce,Li shows a comparable OSL signal intensity following exposure to ionizing radiation, a higher saturation limit (ca 7000 Gy) and a shorter luminescence lifetime (31.5 ns). MgB4O7:Ce,Li is, however, not yet an optimum material for OSL dosimetry, as it exhibits anomalous fading and shallow traps. Further optimization is therefore needed, and possible avenues of investigation encompass gaining a better understanding of the roles of the synthesis route and dopants and of the nature of defects.

Investigation on structural, optical and electrical properties of Zn doped indium oxide thin film for gamma dosimetry

Zinc-doped indium oxide thin film was deposited on the glass substrate using the spray pyrolysis method at a substrate temperature of 723K for various Zn concentrations in the range of 2–10 at%. The obtained film confirmed a polycrystalline cubic structure with a shift in preferred growth orientation from (400) to (222) on higher doping levels. The morphological study also exhibited a microstructure change which corroborates with the XRD spectra. Moreover, surface morphology has a great influence on the physical properties of the film. Cubic crystallization of doped In2O3 with no impurity phase and the presence of oxygen vacancies is confirmed by Raman spectra. It also confirms the In substitution by Zn. Optical transmittance decreased with doping which is supported by a decrease in bandgap energy from 3.68 to 3.5. The Refractive index is estimated using three different models with the Herve-Vandamme model showing the least deviation. Urbach energy shows an inverse relation with energy band gaps. Violet-blue emission was observed in the photoluminescence spectra. Zn doping also had an influence on the electrical properties of the material. Thermoluminescence spectroscopy validates Zn-doped In2O3 films' suitability for gamma dosimetry. XPS peak intensity corresponds to oxygen vacancies observed to be higher for Zn doped sample relative to undoped, indicates the formation of defects after doping. The resistivity increased up to 6 at% and then decreased, which can be due to the preferred orientation change to (222) at higher dopant concentrations. From the investigation, it is concluded that 4% Zn doped In2O3 can be used for sensor applications due to its good structural, optical and electrical properties and also lesser defects.

Advanced Thermoluminescence Spectroscopy as a Research Tool for Semiconductor and Photonic Materials: A Review and Perspective

Thermoluminescence (TL) or thermally stimulated luminescence (TSL) spectroscopy is based on liberating charge carriers from traps in the bandgap by providing enough thermal energy to overcome the potential barrier of the traps. It provides a powerful tool to measure the positions of the localized states/traps in the bandgap. Despite that, its applications in semiconductors are very limited. Herein, the basics of TL spectroscopy and the recent advances in the technique with focus on cryogenic thermally stimulated photoemission spectroscopy (C‐TSPS) which extends TL measurements to cryogenic regime and allows the detection of very low concentrations of shallow and deep localized states is discussed. One goal herein is to introduce the reader to the use of TL and C‐TSPS in the characterization of semiconductors, explaining how it can be applied and demonstrating its advantages as a powerful tool for measuring shallow donor/acceptor ionization energies in semiconductors and as a method for characterizing compensating defects. The article also discusses interesting potential applications of C‐TSPS in new research areas such as corrosion and formation of oxide layers on metal surfaces.

Introducing cation disorder to enhance thermal stability in LuY3(BO3)4: Eu3+ phosphors for pc-WLEDs

Thermal quenching is a serious drawback that limits the application of phosphor-converted white light-emitting diodes (pc-WLEDs), because the operating temperature of phosphors tends to increase, resulting in emission loss due to non-radiative transitions. Herein,by introducing Lu3+ ions and Eu3+ ions into YBO3 to create lattice distortion and cation disorder, a series of Lu1-xY3(BO3)4: xEu3+ red phosphors have been designed to obtain novel phosphors with excellent thermal stability. The phosphors were synthesized by the traditional high-temperature solid-phase method. XRD results and EDS energy spectrum access the phase composite and crystal structure. Under 393 nm excitation, Lu1-xY3(BO3)4: xEu3+ phosphors emit red light peaking at 594 nm, 613 nm, and 651 nm Lu0.6Y3(BO3)4:0.4Eu3+ and Lu0.2Y3(BO3)4:0.8Eu3+ can maintain 93% and 86% emission intensity respectively at 150 °C, and they can still maintain 90.2% and 78% respectively at 200 °C. Thermoluminescence spectroscopy proves that the Lu0.2Y3(BO3)4:0.8Eu3+ phosphor has deep defects at 145 °C and 400 °C, which can release electrons to compensate for the emission intensity at high temperatures, thereby improving thermal stability.The prepared phosphor has extremely high thermal stability and particularly high color rendering purity (99.8%). Under the driving current of 120 mA, the color rendering index of the pc-WLED packaged with Lu0.2Y3(BO3)4:0.8Eu3+ phosphor powder is 89.4, and the correlated color temperature is 4681K.All these results indicate that LuY3(BO3)4:Eu3+ phosphors are promising for pc-WLED applications, especially for applications requiring high temperature operating conditions.

A novel blue emitting europium doped lanthanum magnesium hexaaluminate long persistent phosphor and analysis of traps distribution

Long persistent luminescent (LPL) materials are highly anti attention due to its energy conservation and environmental protection. Here, a novel blue LPL material LaMgAl11O19: Eu2+ (LMAO: Eu2+) have been synthesized successfully by high temperature solid state method, and its LPL properties was studied for the first time. The X-ray diffraction, refinement and crystal structure were used to characterize the phase composition of the synthesized samples. The LMAO: Eu2+ phosphor mainly exhibits blue center at 454 nm, which was mainly attributed to the 5 d-4f transition of Eu2+. The LPL properties were characterized by the LPL decay curves, LPL spectrum and the thermoluminescence (TL) curves. After removing the excitation sourc e, a blue LPL is produced approximately 9 min. Finally, the trap distribution and LPL mechanism are analyzed in detail through TL spectroscopy.

Abnormal Self-Reduction Phenomenon of Europium-Doped Borate and Its Luminescence Properties

In this work, mixed-valence Eu-doped Ba2AlB4O9Cl (BABOC) was successfully synthesized in an air atmosphere for the first time. The samples were determined to possess a good single phase by Rietveld structure refinement and X-ray powder diffraction (XRD). The luminescence spectra of the samples showed that the characteristic emission and excitation peaks of Eu2+ and Eu3+ were both present in the sample, and their emitting color could be adjusted by changing the Eu doping concentration. The band gap of BABOC, calculated by density functional theory (DFT), was found to be 4.70 eV and was confirmed by diffuse reflection spectroscopy (DRS). The relationship between the self-reduction efficiency of the sample and the doping concentration of Eu ions was studied by measuring the decay lifetimes of Eu2+ and Eu3+. The thermal quenching and thermoluminescence spectroscopy of the samples were also studied in detail. All of the results indicated that BABOC:Eu has special self-reduction properties, and the abnormal self-reduction phenomenon was explained by a charge compensation model. Our investigation of BABOC:Eu provides practical evidence and a theoretical basis for the self-reduction phenomenon and a new method to further modify the luminescence properties of phosphors.

Energy transfer to luminescent impurity by thermally quenching excitons in CdWO4:Sm

CdWO4:Sm single crystals were studied by optical, electron-paramagnetic and thermoluminescence spectroscopy in the temperature range of 4–750 K. A hopping diffusion of self-trapped excitons and energy transfer to Sm3+ centres is demonstrated. The mechanism of energy transfer includes the formation of a Sm3+ bound exciton either by direct excitation or in the result of a thermally stimulated hopping diffusion of self-trapped excitons as well as a sequential trapping of charge carriers near the Sm3+ ions. The energy transfer from the perturbed excitons to Sm3+ ions is controlled by an electric dipole-dipole or exchange interaction and it is terminated in the temperature range of 450–650 K due to the thermal destruction of Sm3+-perturbed excitons. In the case of near-surface excitations created in the energy region of high absorption coefficients by 5-eV photons, the Sm3+ emission is additionally quenched by surface-induced quenching centres.

Thermoluminescence properties of MgO:Al3+,Li+ prepared by microwave-assisted solution combustion method

In this work, the thermoluminescence (TL) properties of MgO co-doped with Al3+ and Li+ cations, prepared by microwave-assisted solution combustion synthesis, using glycine as a fuel, are presented for the very first time. The X-ray diffractometer pattern confirmed MgO:Al3+,Li+ cubic phase formation and showed minor presence of a secondary phase associated with Al3+ cations. The energy band gap of the sample was approximated to 3.52 eV using the Kubelka-Munk relation. TL spectroscopy equipped with a beta source for sample irradiation was used to investigate electron trapping centres of MgO:Al3+,Li+. The dose-response measurements confirmed the general order kinetics. The depth of these electron trapping centres was approximated to be from 0.70 to 0.81 eV.

Lanthanide Ions as Local Probes in Ionic Hydrides: A Pulsed Electron Nuclear Double Resonance and Thermoluminescence Study of Eu2+-Doped Hydride Perovskites

A model study on the use of pulsed electron paramagnetic resonance spectroscopy and optical spectroscopy of Eu2+ as a local probe in hydrides is presented for the Eu2+-doped (and codoped) perovskites LiMH3 and LiMD3 (M = Sr or Ba). Two-pulse field-swept electron spin echo, Davies and Mims electron nuclear double resonance, Davies-type difference triple resonance experiments, and thermoluminescence spectroscopy, as well as density functional calculations, were carried out. Electron nuclear double resonance spectroscopy allows for an unambiguous determination of the position occupied by the dopant ion, which is important information necessary for the correct interpretation of optical spectra. With regard to the current importance of hydrides and mixed anionic hydrides, doping with rare-earth or transition-metal ions and the combination of pulsed EPR and optical spectroscopy may serve as a promising and convenient tool for studying such materials.

Study of trap levels in β-Ga2O3 by thermoluminescence spectroscopy

Electronic defects with shallow and deep levels in β-Ga2O3 single crystals were investigated by thermoluminescence (TL) spectroscopy. Undoped, Fe-doped, Sn-doped, and Mg-doped β-Ga2O3 single crystals grown by different methods were studied, and thermal activation energies of defects were calculated using the initial rise method. Hall-effect measurements and optical absorption spectroscopy were performed to determine the electrical transport properties and optical bandgaps. It was found that the dopants do not have any effect on the bandgap energy, which is important for comparing the trap levels in the samples. Three deep trap levels were found in the undoped crystals; the activation energy, ED, and concentration of defect centers for all of them have slightly changed after doping with Fe and Mg. Fe doping induced an additional defect center with activation energy of 0.62 eV. The measurements revealed the absence of TL emission in Sn doped crystals indicating that Sn doping may quench luminescence centers or modified some original electronic defects to inactive electron traps. The second interpretation “decrease of traps” may align with the successful incorporation of Sn as a donor and the high conductivity of Sn doped crystals revealed from Hall-effect measurements. This work also illustrates that the semi-insulating characteristics of Fe and Mg doped Ga2O3 are associated with the increase of the concentration of original traps in the crystal as well as the formation of new electron traps acting as deep acceptors. Recombination centers in all crystals are assumed to be associated with iron impurities.

Structure, photoluminescence and thermoluminescence study of a composite ZnTa2O6/ZnGa2O4 compound doped with Pr3+

The study of persistent luminescence is interesting for applications related to biological imaging, self-lit roads and security signs. Composite Pr-doped samples were prepared in one pot by solid chemical reaction at 1200°C for 4h. The X-ray diffraction patterns of the samples showed mixed phases which correspond to ZnGa2O4 and ZnTa2O6 phases. Interestingly, the secondary electron microscopy images showed that the surface morphology is composed of particles with different shapes: irregular, rhombus and rod shapes. The X-ray maps obtained using field emission scanning electron microscopy, confirmed that the irregular particles correspond to ZnTa2O6, and the rods correspond to ZnGa2O4. Red emission was observed from 1D2→3H4, 3P0→3H6, 3P0→3F2 and 1D2→3H5 transitions of Pr3+. The lifetime of the persistent luminescence was measured, and the corresponding trapping centres were investigated using thermoluminescence spectroscopy.