Thermoluminescence Spectra Research Articles

Thermoluminescence properties of the Li2B4O7:Dy3+,Ce3+ glasses and their application potential in the dosimetry field

In this study, we have successfully fabricated the lithium-borate glasses co-doped with Ce3+ and Dy3+ ions (Li2B4O7:Ce3+,Dy3+ or LBO: Ce3+,Dy3+) using the melt quenching technique. Our main purpose is to study the thermoluminescence (TL) characteristics and application potential of the material in the dosimetry area. The TL properties of the Li2B4O7:Ce3+,Dy3+ glasses were studied through the glow curve and TL spectra. The thermoluminescence mechanism for these glasses has been proposed. The optimal conditions for studying of the TL process have been found for the Li2B4O7:Ce3+,Dy3+ glasses. The kinetic parameters of the main peak (225 °C), for example, the activation energy, lifetime, and frequency factor of the electronic trapping centers were analyzed using the peak shape method. The important factors to estimate the application potential of the material, such as the relative sensitivity, linear responses, dose detection threshold, mean standard deviation, fading rate, reproducibility, and intrinsic precision have been studied in detail. The obtained results showed that the Li2B4O7:Ce3+,Dy3+ glasses have a high potential for dosimetry applications in medical and food irradiation.

Multifunctional Near-Infrared Luminescence Performance of Nd3+ Doped SrSnO3 Phosphor

The phosphors with persistent luminescence in the NIR (near-infrared) region and the NIR-to-NIR Stokes luminescence properties have received considerable attention owing to their inclusive application prospects in the in vivo imaging field. In this paper, Nd3+ doped SrSnO3 phosphors with remarkable NIR emission performance were prepared using a high temperature solid state reaction method; the phase structure, morphology, and luminescence properties were discussed systematically. The SrSnO3 host exhibits broadband NIR emission (800–1300 nm) with absorptions in the near ultraviolet region. Nd3+ ions emerge excellent NIR-to-NIR Stokes luminescence under 808 nm laser excitation, with maximum emission at around ~1068 nm. The concentration-dependent luminescence properties, temperature dependent emission, and the luminescence decay curves of Nd3+ in the SrSnO3 host were also studied. The Nd3+ doped SrSnO3 phosphors exhibit exceptional thermal stability; the integrated emission intensity can retain approximately 66% at 423 K compared to room temperature. Most importantly, NIR persistent luminescence also can be observed for the SrSnO3:Nd3+ samples, which is in the first and second biological windows. A possible mechanism was proposed for the persistent NIR luminescence of Nd3+ based on the thermo-luminescence spectra. Consequently, the exciting results indicate that multifunctional NIR luminescence has been successfully realized in the SrSnO3:Nd3+ phosphors.

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.

An investigation on thermoluminescence properties and kinetic parameters of Çankırı rock salt

This study investigates the thermoluminescence (TL) dosimetric properties and kinetic parameters of natural salt samples sourced from the Çankırı rock salt cave in Turkey using β irradiation. Obvious effective TL maximum observed at around 85 and 230°C. A preheat condition was determined to apply a thermal cleaning for the lower temperature side of TL spectrum. Dose sensitivity, linearity and reusability characteristics were investigated for effective TL maximum on the high temperature side of the spectrum. TL kinetic parameters were determined via various heating rates (VHR) experiment, and whole TL glow curve was studied via Tm−Tstop experiment and glow curve deconvolution. General order kinetics approach was utilized for glow curve deconvolution analysis. Kinetic parameters were determined for at least eight electron trap levels which has activation energies in the range of 0.8–1.53 eV.

Intense and sensitive green mechanoluminescence by Tb3+ doping in Y3GaO6

In this study, an efficient mechanoluminescent material, namely Y3GaO6:Tb3+, with green emission was prepared by high-temperature solid-phase synthesis. X-ray diffraction (XRD) shows that the samples belong to the orthorhombic crystal system with the space group Cmc21. The luminescence intensity of the materials is related to the content of the luminescent centers, and both photoluminescence (PL) and mechanoluminescence (ML) show that the optimum doping level of Tb3+ is 0.07. In both tensile and frictional applications, the ML intensity is linearly correlated with the magnitude of applied stress. Analysis of the thermoluminescence (TL) spectra indicates that the ML of the material arises from carriers released from the trap under stress stimulation, thus revealing its mechanism of ML property. Finally, the study demonstrates the mechanoluminescence pattern of Y3GaO6:Tb3+.

Preparation and anti-counterfeiting application of Sr3Y2Ge3O12:Bi2+ red long afterglow luminescent

Red, as one of the three primary colors, is crucial for blending the luminescent color of long-lasting materials. This project selected Sr3Y2Ge3O12 as the substrate and Bi2+ as the activator. A solid-state method at high temperature was used to prepare a new type of visible red long-afterglow luminescent material, by adjusting the doping concentration of Bi2+ and changing the calcination temperature. When the doping concentration of Bi2+ was 0.50mol% and the calcination temperature was 1150 °C, the prepared Sr3Y2Ge3O12:Bi2+ had the best luminescent properties. After being excited by 254 nm ultraviolet light, the material shows the red afterglow luminous intensity, duration and stability that meet the practical application requirements. Through thermoluminescence, photoluminescence and fluorescence spectra, the trap characteristics and internal mechanism of long afterglow were studied comprehensively. Finally, the film and printing ink were prepared by using the Sr3Y2Ge3O12:Bi2+ long afterglow luminescent powder with the best luminescent performance, and the pattern anti-counterfeiting was successfully realized.

Co-doping Sm3+ transforms Y2Ge2O7:Pr3+ into a novel orange-reddish long afterglow phosphor

Red long afterglow phosphors have significant implications for the realization of multicolor long-afterglow phosphors, but their insufficient luminescence intensity and afterglow duration still cannot meet the demands of practical applications. In this study, a novel orange-red phosphor, Y2Ge2O7:Pr3+, was synthesized for the first time. This phosphor not only exhibits exceptional thermal resistance but also shows a marked enhancement in long-afterglow performance upon co-doping with Sm3+. Remarkably, an orange-red afterglow can still be distinctly observed with the naked eye even 5 min after the removal of the excitation source in darkness. Further investigations involving thermoluminescence spectrum tests and the construction of an independent host-referred binding energy (HRBE) diagram reveal that the introduction of Sm3+ effectively mitigates the trap depth (1.02 eV) of the Y2Ge2O7:Pr3+ phosphor and significantly augments the quantity of electrons in shallow traps. This modification facilitates the effective release of electrons under room temperature conditions by the improved phosphor, thereby actualizing the long-afterglow luminescence phenomenon. Additionally, our findings indicate that a trap depth within the range of 0.60–0.80 eV is the optimal range for releasing electrons at room temperature. This research offers a crucial reference for future endeavors aimed at enhancing the performance of long-afterglow phosphors.

Mechanism and dynamic analysis of persistent luminescence in phosphors Sr2MgSi2O7: Eu2+, Dy3+

The persistent luminescent (PSL) phosphors Sr2-x-yMgSi2O7: xEu2+, yDy3+ (x = 0∼0.08, y = 0∼0.08) were synthesized by a solid-state reaction method in a weak reductive atmosphere of 5%-H2/N2. Comprehensive measurements were carried out to study the effects of Eu2+ and Dy3+ doping amount on the crystal phase, photoluminescence (PL), afterglow decay properties, and trap energy levels. The results indicated that the impurity phases decreased and disappeared, and crystalline grains tended to be larger and denser with the doping amount of Eu2+ and Dy3+ increasing. We shed light on the origination of asymmetric PL peak, concentration quenching of Eu2+ ions, time evolution of PSL specture and chromaticity of Eu2+, Dy3+ co-doped phosphors. Based on the deconvolutions of X-ray photoelectron spectroscopy (XPS) spectra and thermoluminescence (TL) spectra, the types and energy depth of traps in these phosphors were systematically studied. According to the data of PL, PLE, and TL, we deduced a schematic diagram of the energy level and discussed the mechanism of PSL of the phosphors. As Dy3+ dopant increases, the Eu2+, Dy3+ co-doped phosphors not only generate more defects of VO•• and VSrʺ, but also introduce DySr• defect with proper trap depth, meanwhile, a thermally assisted tunneling mechanism will gradually dominate during the persistent luminescence, which is responsible for that the phosphor with x = 0.02, y = 0.01 presents the best long afterglow property.

Trap-controllable near-ultraviolet elastico-mechanoluminescence of Ce3+ doped phyllosilicate with melilite-type structure.

Mechanoluminescence (ML) materials have attracted much attention because of their mechano-optical conversion characteristics, which have shown broad application prospects in stress sensing and anti-counterfeiting technology in the past few decades. However, elastico-ML has not been demonstrated at the near-ultraviolet (NUV) range. In this study, a novel NUV elastico-ML material (Ca, Sr)8Mg3Al2Si7O28:Ce3+ (CSMASOC) with a melilite-type structure is successfully developed. The ML properties of CSMASOC were optimized by adjusting the doping concentration of Ce3+ and cation substitution, and the ML mechanism was also explored by analyzing the ML test under different irradiation conditions and thermoluminescence spectra. The results confirmed that the ML in CSMASOC was derived from 5d-4f transition of Ce3+, and CSMASOC belongs to trap-controllable ML material. In addition, NUV ML material CSMASOC is combined with several commercial phosphors, and constructed multi-color ML in the visible light range. The developed NUV ML materials and the constructed multi-color ML system in this work are critical for expanding the types of ML materials and promoting the practical application of ML materials.

Thermoluminescence studies of a Gothic church in Świebodzin from Silesia in Poland

The paper presents thermoluminescence (TL) studies that aim to establish the possibility of using such analysis to determine the date of the construction, transformation and/or rebuilding of a historical church. The determination of the age of building structures using the form of absolute dating that is now used by architects and archeologists is difficult and complex. A relatively large error of estimation can be observed in archeological studies. In the case of samples from the Middle Ages, such errors are not acceptable. The authors attempted to develop an alternative spectroscopic TL method for such studies, and proposed that the composition of bricks should be measured using X-ray diffraction, electron microscopy (EM) and TL spectra. The bricks for the testing were taken from internal walls and the walls in the attics of churches, i.e. from places built during the last stage of construction works. The TL measurements were made using x-ray and β source excitation within the temperature range of 25–500°C. Two different sizes of grains were studied: small (∼0.1 mm) and large (∼0.5 mm). A gothic church in Świebodzin from 1555, which has a well-known history of its construction, was selected for the investigations. Due to the fact that this church is 326 years younger than the two churches evaluated and described in [1], the composition of its bricks could be different. Therefore, the authors decided to compare the XRD data, EM results and TL spectra for bricks taken from all three churches. The intensities of the TL and the integrated TL intensities were determined. The measurement results are important for creating a relationship between the TL intensity and the date a building object was constructed. Moreover, thanks to this it was possible to verify the construction date of Saski Palace in Warsaw.

Smart windows based on ultraviolet-B persistent luminescence phosphors for bacterial inhibition and food preservation

Herein, ultraviolet B (UVB) persistent luminescence phosphors containing SrAl12O19: Ce3+, Sc3+ nanoparticles were reported. Thermoluminescence (TL) spectrum analysis reveals that the shallow trap induced by Sc3+ co-doping plays an important role in photoluminescence persistent luminescence (PersL) development, while the deep trap dominates the generation of optical stimulated luminescence (OSL). Owing the appearance of deep trap, the OSL is observed under light (700 nm - 900 nm) excitation. UVB luminescence exerts good bactericidal effects on pathogenic bacteria involved in the process of food spoilage. Thus, the smart window with SrAl12O19: Ce3+, Sc3+/PDMS produces UVB PersL to efficiently inactivate Escherichia coli and Staphylococcus aureus. In addition, the presence of the smart window delays the critical point of pork decay, and greatly reduces the time of pork spoilage. It maximizes the convenience of eradicating bacteria and preserving food, thus offering a fresh perspective on the use of UV light for food sterilization and preservation.

Extended study of the influence of europium doping on phosphate glass

The phosphate glasses with various Eu2O3 concentrations (0.1–3.0 w/w%) were synthesized and studied regarding the influence of europium dopant on the properties of irradiated phosphate glasses. During studies, samples were irradiated using two types of ionizing radiation sources (β− and γ), with obtained doses up to 40 kGy. TL studies were investigated using various methods, such as TL response vs. radiation dose and the TMax-Tstop method. To further investigate, if increasing the europium concentration affects the structure of electron traps, Computer Glow Curve Deconvolution studies linked with various heating rates methods were applied –increasing the concentration of dopant does not influence the number and energy of electron traps in irradiated samples. This fact was also supported by the results of the thermoluminescence spectrum – where no additional signals, besides wide signals from native glass were observed. OSL and IRSL studies were also conducted, for OSL we observed quenching of the signals, similar as in the TLD case. For IRSL studies all samples didn't display any signals. Finally, to understand if Eu3+ also has a “protective” effect, decreasing the yield of generating F-centers during irradiation, UV-VIS spectroscopy was used. It was established that samples doped with europium oxide possess ca. 20% lower signals at F-center maximum (at 475 nm), the building-up maximum at 320 nm was observed, characteristic of the absorption band of Eu2+. All data indicate that europium in phosphate glass is taking the role of an efficient electron quencher. This quenching phenomenon occurs in three ways: first (direct) when the ion reduction process (Eu3+→Eu2+) competes with the formation of F-centers, and second (indirect) when during heating electrons coming from F-centers were quenched by near Eu3+ ions. The third mechanism of quenching occurs through the electron's non-radiative transition induced by increased stress in the glass matrix caused by a large ionic radius of the dopant.

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.

Defects‐Induced Photochromism and Luminescent Modulation Based on Lanthanides‐Doped Cadmium Glass Toward Optical Storage Applications

AbstractOwing to the large storage capacity, the transparent luminescent glass with photo‐induced coloration properties has attracted considerable interest in recent years. However, lots of the photochromic (PC) mechanisms for glass are related to the ionic valence transformation, and the study associated with the defects‐induced photochromism of glass is limited. Herein, a kind of Sm3+ doped PC cadmium glass is fabricated, for which the PC mechanism is systematically investigated by various techniques, such as XPS spectra, thermoluminescence spectra, EPR spectra, etc. The results show that the mechanism of coloration for such glass should be due to the presence of oxygen vacancy‐related electron centers. Under 365 nm light irradiation, the color of the glass turns from colorless to brown, exhibiting a large color contrast, of 62%. Utilizing the re‐absorption process between absorption spectra and emission/excitation spectra, the emission intensity of Sm3+ is reversibly regulated, indicating their promising applications as an optical storage medium.

Dual-mode optical thermometry and multilevel anti-counterfeiting based on Er3+/Eu3+ doped Ba5Gd8Zn4O21 phosphors

Designing and manufacturing novel anti-counterfeiting materials with multilevel, strong readability and inexpensive is a crucial challenge. Herein, a batch of Ba5Gd8(1-x-y)Zn4O21:xEu3+/yEr3+ phosphors with long persistent and multicolor luminescence were synthesized. Their structure and luminescence properties were studied through X-ray diffraction, scanning electron microscope, lifetime decay curves, emission, excitation, thermoluminescence and diffuse reflection spectra. Under different wavelengths irradiation, Ba5Gd8Zn4O21:Eu3+, Ba5Gd8Zn4O21:Er3+ and Ba5Gd8Zn4O21:Eu3+, Er3+ emit strong red, green and multicolor (green, yellow, red) luminescence, respectively. Importantly, Ba5Gd8Zn4O21:Eu3+ and Ba5Gd8Zn4O21:Eu3+, Er3+ phosphors exhibit long-lasting luminescence after 254 nm and X-ray radiation. Combine long afterglow and multicolor emissions under X-ray, UV and 980 nm laser excitation, these materials successfully achieve multilevel anti-counterfeiting. In terms of optical temperature measurement, the maximum relative sensitivity of Ba5Gd7.44Zn4O21:0.07Er3+ based on thermal coupling levels (2H11/2/4S3/2) and non-thermal coupling levels (4F9/2/2H11/2) of Er3+ are 1.29 % K−1 and 0.34 % K−1, respectively. Both two modes exhibit superior repeatability (98 %) in 333–573 K temperature range which can realize self-calibration temperature sensing. All findings reveal great potential of these phosphors for multilevel anti-counterfeiting and efficient optical temperature sensing.

Li9Mg3[PO4]4F3 fluorophosphate as a new thermoluminescent material: Experimental and theoretical study

In this work, radioluminescence (RL), thermoluminescence (TL) and photoluminescence (PL) of fluorophosphate Li9Mg3[PO4]4F3 as a possible dosimetry material are studied for the first time. It was found that the irradiated sample exhibits significant thermoluminescence in the temperature range of 100–300°С with the main peak at 205°С. The RL, PL and TL spectra consist of one broad band centered at 400 nm which was attributed to defects in the structure of Li9Mg3[PO4]4F3. The energy required to excite defects in Li9Mg3[PO4]4F3 determined by UV–vis spectroscopy is 4.4 eV (λ ≈ 280 nm). Additional evidence for intrinsic defects was obtained from the electron paramagnetic resonance (EPR) in Li9Mg3[PO4]4F3. The DFT method was employed to simulate various defects including single and complex, neutral and charged vacancies. The formation energies of vacancies were predicted and their effect on the electronic structure and optical properties was established. These intrinsic defects introduce additional electronic states into the band gap and absorption bands in the visible region, the position and intensity of which strongly depend on the type of defect. Our experimental and theoretical studies reveal that Li9Mg3[PO4]4F3 can be a promising optical matrix suitable for dosimetric applications. As evidence, the main functional characteristics of the new material are given.

Enhanced Thermal Stability of Red‐Emitting Sr2Si5N8:Eu2+ Phosphors from Triggered Applicable Trap Level via Rare Earth Ions Co‐Doping

AbstractTo solve the problem of thermal stability of the red‐emitting phosphor Sr2Si5N8:Eu2+ with great valuable luminescence performance, trivalent rare earth ions Ln3+ (Ln = Dy, Ho, Er, Tm, Nd, and Pr) are co‐doped into Sr2Si5N8: Eu2+ lattice to form thermally robust phosphors Sr2Si5N8:Eu2+,xLn3+(Lnx‐258, 0 ≤ x ≤ 0.05). The successful incorporation of rare earth ions in the crystal structure and the regulation of luminescent properties are proven by a variety of material characterization techniques and analysis. Although the co‐doping of the selected rare earth ions reduces the luminescence intensity of the phosphor, the Dy0.01‐258 sample still has a high external quantum efficiency (EQE) of 78.6%. More importantly, the co‐doping of Dy3+ with x = 0.01 significantly improves the luminescent thermal stability of phosphors at high temperature and the luminescence intensity of Dy0.01‐258 samples at 200 °C can be maintained at 94.7% of room temperature. The thermoluminescence spectrum shows that the defects brought about by co‐doping of Dy3+ with x = 0.01 introduce trap energy levels, which can compensate for the Eu2+ luminescence at high temperature. At the same time, the cathodoluminescence mapping and spectra show that the phosphor has a high saturation current under high‐energy electron bombardment, which indicates that this nitride phosphor also has the potential to be used in field emission display (FEDs). Based on its extraordinary EQE and thermal stability data, this nitride phosphor is the first‐rate among the red phosphors for pc‐wLEDs, and has excellent application prospects in FEDs.

Thermoluminescence studies of Sm3+ doped ZnB2O4 phosphor

Solid-state reaction method was used to prepare the rare earth Sm3+ doped ZnB2O4 phosphors. The structural characterization of Sm3+ doped ZnB2O4 samples was recorded by X-ray diffraction (XRD) technique. A single phase structure similar to the standard JCPDS files-39-1126 was recorded using XRD. The graph plotted between TL intensity a nd temperature for different UV dose was recorded. The highest TL intensity was recorded for 20 minutes of UV dose. On further increase in the exposure dose, decrease in TL intensity was observed. The thermo-luminescence was recorded with varying percentage of Sm3+. The at most TL intensity was obtained with 3 mol% of Sm3+. The thermo-luminescence spectra of ZnB2O4 and Sm3+ doped ZnB2O4 phosphors were also studied.

The role of defects in thermoluminescence of pure and rare-earth-doped magnesium tetraborate phosphor

The aim of this work was to elucidate the role of defects in energy storage and transfer in X-ray irradiated MgB4O7. Pure and terbium- and erbium-doped magnesium tetraborate was synthesized by the solid state reaction method. The band gap value Eg = 9 eV was estimated using the method of X-ray photoelectron spectroscopy (XPS). Absorption attributed to defects with energy levels located in the forbidden band was found from UV–vis spectroscopy. An interpretation of the thermoluminescence and radioluminescence spectra of pure and doped magnesium tetraborate was proposed. Two different mechanisms for enhancing the thermoluminescent response of MgB4O7 upon doping with rare earth elements were demonstrated.

RADIATION DEFECTS IN ZrO<sub>2</sub> NANOSTRUCTURAL COMPACTS IRRADIATED BY ELECTRON AND ION BEAMS

The thermoluminescence (TL) and EPR spectra of nanostructured compacts of monoclinic ZrO2 irradiated by three types of irradiation have been studied: impulse flow of 130 keV electrons, beam of 10 MeV electrons, as well as a 220 MeV Xe ion beam. Irradiation of samples with 10 MeV electrons and ions leads to the formation of F+ centers in them. Thermal destruction of these centers is observed in the temperature range 375–550 K for electron-irradiated compacts and 500– 700 K for ion-irradiated compacts. The drop in the concentration of F+ centers is associated with the depletion of traps responsible for TL peaks in the specified temperature range. In samples irradiated with an ion beam, new paramagnetic centers with g = 1.963 and 1.986 were found, in the formation of which, probably, Zr3+ ions and oxygen vacancies participate, thermal destruction occurs in the temperature range 500–873 K.