Thermally Stimulated Luminescence Glow Curves Research Articles

Thermally Stimulated Luminescence in ZnSe:Ag and ZnSe:(Ag, Gd) Phosphors

AbstractWith a view to understanding the luminescence mechanism in ZnSe, a systematic study of thermally stimulated luminescence (TSL) of UV ray (3650 Å) irradiated ZnSe:Ag and ZnSe:(Ag, Gd) phosphors has been undertaken. TSL glow curves of these phosphors are recorded in the temperature range 110–340 K. The TSL parameters like trap depth, frequency factor, order of kinetics, and capture cross‐section of the glow peaks are evaluated employing Cutie's method, various heating method, and peak shape method.

Paramagnetic radiation-induced radicals in calcium pyrophosphate polymorphs

Calcium pyrophosphate (Ca2P2O7) is a promising material for biomedical and optical applications; however, relatively little is documented on the radiation-induced point defects of the material. This study reports on the formation, identity, and properties of X-ray-induced radicals in γ-, β-, and α-polymorphs of Ca2P2O7. Complementary thermally stimulated luminescence (TSL), electron paramagnetic resonance (EPR), and solid-state nuclear magnetic resonance (NMR) spectroscopy techniques were combined to reveal the effects of ionising radiation on each polymorph. The high temperature polymorphs β-, and α-Ca2P2O7 exhibited diminishing variety and intensity of EPR signals, whereas the opposite trend was observed in the TSL response. TSL glow curves consisted of multiple peaks in the temperature range of 20–350 °C, with maximum emission intensity located at approximately 600 nm. Multiple electronic spin 1/2 paramagnetic centres were identified on the basis of spin-Hamiltonian parameters determined from EPR spectra simulations. Annealing kinetics of the individual paramagnetic centres were determined to provide an interpretation of the complex nature of TSL glow curves. A decrease of the 31P spin-lattice relaxation T1 times after irradiation was detected for all Ca2P2O7 polymorphs. The results highlight the importance of structure, morphology, and synthesis conditions on the formation of charge traps in Ca2P2O7 and expand the knowledge base on the variety of radiation-induced radicals in phosphate materials.

Ce-doping effect on dosimetric properties of mullite single crystals synthesized by the floating zone method

We synthesized the 0.1, 0.5, 1.0, and 1.5% Ce-doped mullite single crystals by the floating zone method and evaluated their photoluminescence (PL) and thermally stimulated luminescence (TSL) properties. The single-phase orthorhombic structure was confirmed in all the samples from powder X-ray diffraction patterns. The transmittance spectra of all the samples showed the absorption related to the 4f-5d transitions of Ce3+ ions and optical band gap of mullite. The Ce-doped mullite single crystals had the PL attributed to the 5d-4f transitions of Ce3+ ions. In TSL properties, TSL glow curves had the glow peaks at 250 and 370 °C, and TSL spectra heated at 250 and 370 °C had the peak at around 390 nm owing to the Ce3+ ions. TSL dose response functions showed linear response from 0.01 mGy to 10 Gy for the 1.0% Ce-doped mullite single crystal and from 0.1 mGy to 10 Gy for the 0.1, 0.5, and 1.5% Ce-doped ones. The 1.0% Ce-doped mullite single crystal could be used multiple times for dosimetry. In addition, the TSL intensity of the 1.0% Ce-doped mullite single crystal after 7 days from X-ray irradiation was about 82.4% from immediately one after X-ray irradiation.

Synthesis of Tb-doped SiO2 glasses by spark plasma sintering method and evaluation of photoluminsecence and thermally stimulated luminescence properties

Tb-doped SiO2 glasses were synthesized by the spark plasma sintering (SPS) method, and optical and thermally stimulated luminescence (TSL) properties were investigated. The diffuse transmittance spectra of the 0.01, 0.05, and 0.1% Tb-doped SiO2 samples included the absorption due to the 4f-5d transitions of Tb3+ ions. In photoluminescence properties, all the Tb-doped SiO2 samples showed several emission peaks due to the 4f-4f transitions of Tb3+ ions and oxygen deficiency vacancy (ODC). The TSL glow curves indicated the glow peak at 140 °C, and only the emission peaks attributed to the 4f-4f transition of Tb3+ ions were observed in TSL spectra of the 0.01, 0.05, and 0.1% Tb-doped SiO2 samples. The integrated TSL intensity of the 0.1% Tb-doped samples had a proportional relationship in the range of 0.01–1000 mGy. The TSL intensity of the 0.05% Tb-doped glass after 72 h from X-ray irradiation was about 69% with respect to the one immediately after X-ray irradiation. In addition, the 0.05% Tb-doped SiO2 glass could use the multiple time for TSL dosimetry.

Dy-concentration dependence on dosimetric properties of CaF2 transparent ceramics

In this study, we synthesized Dy-doped CaF2 transparent ceramics with several concentrations and evaluated optical, thermally stimulated luminescence (TSL), and optically stimulated luminescence (OSL) properties. The 0.05, 0.1, and 0.5% Dy-doped samples had diffuse transmittance of approximately 60% at 500 nm, and the absorption band appeared at around 280 nm after X-ray irradiation. The photoluminescence (PL) excitation wavelengths were 255, 295, 325, 350, 360, and 390 nm. When Dy concentration was 0.1%, the PL quantum yield was maximum. The OSL peaks of the Dy-doped samples was observed at 480, 570, and 660 nm by the optical stimulation at 280 nm. The TSL glow curves of the 0.5 and 1.0% Dy-doped samples consisted of the glow peaks at 75, 160, and 200 °C. The minimum detectable dose of the 0.5% Dy-doped sample as the OSL and TSL dosimeters was 15 mGy and 0.28 μGy, respectively.

Optical and thermally-stimulated luminescence properties of Ce-doped Al2O3 transparent ceramics

Optical and thermally-stimulated luminescence (TSL) properties of Ce-doped Al2O3 transparent ceramics were investigated. The transparent ceramics were synthesized by the spark plasma sintering method. The Ce-doped Al2O3 transparent ceramics showed photoluminescence (PL), radioluminescence, and TSL peaking at around 400 nm, caused by 5d-4 f transitions of Ce3+. The PL decay curve consisted of two components with decay time constants of 21 and 43 ns. The TSL glow curves had glow peaks at 71, 130, 184, 251, 284, and 362 °C. The 0.1% Ce-doped Al2O3 transparent ceramic exhibited the maximum TSL intensity among the present samples. The minimum detectable dose was turned out to be 0.03 mGy.

Thermally stimulated luminescence properties of magnesium orthosilicate single crystals doped with Dy3+ ions

In this study, we grew the Dy-doped Mg2SiO4 single crystals by the floating zone method to investigate the photoluminescence (PL) and thermally stimulated luminescence (TSL) properties. All the Dy-doped Mg2SiO4 showed the emission peaks at 480, 580, and 670 nm in PL and TSL spectra, and these peak wavelengths were typical for the 4f–4f transitions of Dy3+ ions. In the TSL glow curves, all the samples had the glow peaks at 50 °C, 200 °C, 280 °C, and 380 °C. The TSL dose response function of the 1% Dy-doped Mg2SiO4 single crystal showed a good linearity across 1–10000 mGy.

Thermal properties of paramagnetic radiation-induced defects in lithium orthosilicate containing breeder material

Lithium orthosilicate (Li4SiO4) containing ceramics are currently being developed as potential solid-state candidate materials for tritium breeding in future thermonuclear fusion reactors. Under the expected operational conditions, the tritium breeding material will be exposed to the simultaneous influence of several strong energetic factors, for example, radiation, temperature, magnetic field, etc. In the present work, thermal properties of the formed and accumulated paramagnetic radiation-induced defects (containing unpaired electrons) in the Li4SiO4 pebbles with a 2.5 wt.% surplus of silicon dioxide (SiO2) were investigated after irradiation with photons of different types and energies: X-rays with an energy up to 45 keV, gamma rays with an average energy of 1.25 MeV, and bremsstrahlung with an energy up to 6 MeV. The photon-irradiated pebbles were analysed using two complementary spectroscopic methods: electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL). Individual signals contributing to the acquired EPR spectra, TSL glow curves and spectra were distinguished, deconvoluted and simulated in order to obtain a more detailed understanding about the local structure, electron configuration, and thermal stability of the accumulated radiation-induced defects. The simulation and deconvolution data were also compared with the results, which have been acquired for the long-term neutron-irradiated pebbles from the HICU experiment (High neutron fluence Irradiation of pebble staCks for fUsion).

Charge trapping processes in hydrothermally grown Er-doped ZnO

Influence of X-ray irradiation on luminescence properties and defects creation was studied in the erbium doped hydrothermally grown ZnO by using the combination of photo- and radioluminescence (PL and RL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR). The photoluminescence properties of the ZnO:Er appeared affected by the X-ray irradiation – the intensity of the zinc vacancy-related red band and exciton-related ultraviolet band were weakened. The irradiation also evoked charge trapping and new centers creation whose type and number depended on Er doping. The X-ray induced defects were oxygen-based hole and electron trapping centers, O− and O2−, respectively. The X-ray irradiation had also influence on shallow donors in the bulk and at the surface of the ZnO nano- and microrods. TSL glow curves consisted of one broad peak with the maximum at about 110 K, its intensity was varying with the changing Er content. The glow peak was correlated with the thermal destruction of the unstable O2− electron trapping centers. Zinc vacancies-based defects participated in the thermally stimulated luminescence as recombination centers for the electrons released from the O2−.

Effect of W and Mo co-doping on the photo- and thermally stimulated luminescence and defects creation processes in Gd3(Ga,Al)5O12:Ce crystals

Photo- and thermally stimulated luminescence characteristics of Gd3(Ga,Al)5O12:Ce single crystals co-doped with W and Mo are investigated in the 85 - 510 K temperature range and compared with the corresponding characteristics of the undoped and Ce3+ - doped Gd3(Ga,Al)5O12 single crystals of similar composition. A strong effect of the W and Mo impurity ions appears in the photoluminescence spectra and temperature dependences of the photoluminescence intensity, afterglow intensity and decay kinetics, thermally stimulated luminescence (TSL) intensity and TSL glow curves, excitation spectra of the TSL glow curve peaks and activation energy of their creation. The obtained results are explained by the enhancement of the intrinsic emission contribution into the luminescence spectrum of Gd3(Ga,Al)5O12:Ce,W and Gd3(Ga,Al)5O12:Ce,Mo due to a large concentration of various W - and Mo - related electron traps in these crystals and, consequently, the O- - type hole centers, as well as intrinsic crystal lattice defects (e.g., cation vacancies needed for the excess positive charge compensation of the W6+ and Mo6+ ions). The influence of the co-doping with W and Mo ions on the scintillation characteristics of Gd3(Ga,Al)5O12:Ce is discussed.

Thermally stimulated luminescence properties of Dy-doped MgAl2O4 single crystals

In this paper, we have prepared Dy-doped MgAl2O4 single crystals by the Floating Zone (FZ) method and investigated photoluminescence (PL), scintillation, and thermally stimulated luminescence (TSL) properties. In PL and scintillation, origins of luminescence at around 480, 580, and 660 nm of synthesized crystals were assigned to the 4f–4f transitions of Dy3+. In TSL, three glow peaks at around 50, 220, and 350 °C were observed, and these peaks were attributed to cation antisites and V center. The 0.1 % Dy-doped MgAl2O4 single crystal showed the highest intensity in TSL glow curves among the prepared crystals and higher sensitivity than those in ceramic-form MgAl2O4.

TSL kinetic parameters and dosimetric properties of TlAlF4 crystal grown by Bridgman technique

Abstract The non-hygroscopic crystal of TlAlF4 was grown by self seeded vertical Bridgman technique. The crystalline phase was confirmed through powder X-ray diffraction measurement and compared with reference data. The effective atomic number (Zeff) of the TlAlF4 compound was calculated about 70.77. The X-ray induced emission spectrum having a very strong luminescence band at 390 nm. Thermally stimulated luminescence (TSL) glow curve measurement shows the peak maximum at 430 K. The kinetic parameters for the main TSL peak were studied using various standard methods. The mean activation energy (E) is calculated to be 0.93 eV and the frequency factor is 4.79 × 1011 s−1. The dose response of the sample was studied using X-ray exited luminescence and TSL glow curves. The sample shows good linearity for measured dose range from 17 to 50 R/min. Thermal fading of the sample was checked over a long period of time and also the reusability of the sample was examined. The main TSL peak at high temperature with high sensitivity to ionizing radiation, good consistency in reusability of TSL signals, linear dose response against delivered X-ray doses in a wide dose range and moderate fading effect are some desirable properties of TlAlF4 crystal for considering radiation dosimetric applications.

Evaluation of quantum yields and thermally stimulated luminescence glow curves of Ag-doped phosphate glasses

The aim of this research is to evaluate quantum yield (QY) values in radiophotoluminescence (RPL) centers and thermally stimulated luminescence (TSL) properties of the Ag-doped phosphate glass. After X-ray irradiation to the Ag-doped phosphate glass, a luminescence center of Ag2+ newly appeared at 650 nm of which QY value was 17.8% when the irradiation dose was 10 Gy. It indicates a monotonic increase with irradiation dose from 0.3 to 30 Gy as the RPL response. On the other hand, the QY value of an original luminescence center of Ag+ decreased from 3.5% to 2.0% by irradiation. The TSL glow curve before preheating consists of two peaks at 80 °C and 350 °C and the initial rise method derived activation energies of 0.48 and 0.93 eV, respectively.

Concentration dependence of dosimetric properties in Ce-doped silicate glasses synthesized by the spark plasma sintering method

We synthesized SiO2 glasses doped with various concentrations of Ce by the spark plasma sintering (SPS) method, and evaluated optical, scintillation, and dosimetric properties. The Ce-doped specimens showed photoluminescence (PL) derived from Ce3+ ions at around 400 nm. The highest PL quantum yield was 86.2% among the prepared specimens. The PL lifetime ascribed to the emission from Ce3+ was 19.7–24.2 ns. A scintillation peak as well as the PL was observed due to Ce3+. In addition, optically-stimulated luminescence (OSL) and thermally-stimulated luminescence (TSL) spectra confirmed that the Ce-doped specimens showed the OSL and TSL caused by Ce3+, respectively. TSL glow curves with broad shape were observed in all the Ce-doped specimens, and the 0.1, 0.5, and 1% Ce-doped specimens showed linearly response from 0.1 to 100 mGy.

An insight into indium effect on the crystal structure and thermoluminescence of LiMgPO4: Combined experiment and ab initio calculations

In this work, indium doped LiMgPO4 is first considered as a dosimetric material. We present studies of the structural properties and thermally stimulated luminescence (TSL), as well as electronic structure of pure and indium doped LiMgPO4. We observed a nonmonotonic shift in the TSL peak with increasing indium concentration (x), which was associated with two different indium sites. We demonstrated that In3+ predominantly replaces Mg2+, but at indium concentration of less than 1%, it occupies the Li+ positions. The variation in indium substitution site affects also the depth of electron traps. Doping of LiMgPO4 with indium changes not only the TSL glow curves, but also the spectra of thermoluminescence. The spectrum of undoped LiMgPO4 consists of two broad bands located in the UV region (λ = 350 nm) and in the red region (λ = 640 nm), while there is only one line (λ = 630 nm) in the TSL spectra of LiMgPO4:In3+. The mechanism of thermoluminescence in pure and indium doped LiMgPO4 is discussed.

Evaluation of dosimetric properties of Li-codoped MgF2:Tb ceramics

Li-codoped MgF2:Tb ceramics with different Li concentrations (0.01, 0.1, 1, and 3 mol%) were prepared by the spark plasma sintering method, and photoluminescence (PL), scintillation, and dosimetric properties were investigated. Sharp peaks due to 4-4 f transitions of Tb3+ ion were observed in all of PL, scintillation, and thermally-stimulated luminescence (TSL). TSL glow curves confirmed that the TSL intensity was increased by Li-codoping without an increase of QY values. Especially, the TSL intensity was the highest in 1% Li-codoped MgF2:Tb, which was approximately 2.2 times larger than that of MgF2 doped with only Tb. Moreover, It was confirmed that the TSL responses of the 0.01, 0.1 and 1% Li-codoped MgF2:Tb ceramics were very sensitive to irradiation dose and showed a good linearity from 0.01 to 1000 mGy.

Modeling and Assessment of Afterglow Decay Curves from Thermally Stimulated Luminescence of Complex Garnets.

Afterglow is an important phenomenon in luminescent materials and can be desired (e.g., persistent phosphors) or undesired (e.g., scintillators). Understanding and predicting afterglow is often based on analysis of thermally stimulated luminescence (TSL) glow curves, assuming the presence of one or more discrete trap states. Here we present a new approach for the description of the time-dependent afterglow from TSL glow curves using a model with a distribution of trap depths. The method is based on the deconvolution of the energy dependent density of occupied traps derived from TSL glow curves using Tikhonov regularization. To test the validity of this new approach, the procedure is applied to experimental TSL and afterglow data for Lu1Gd2Ga3Al2O12:Ce ceramics codoped with 40 ppm of Yb3+ or Eu3+ traps. The experimentally measured afterglow curves are compared with simulations based on models with and without the continuous trap depth distribution. The analysis clearly demonstrates the presence of a distribution of trap depths and shows that the new approach gives a more accurate description of the experimentally observed afterglow. The new method will be especially useful in understanding and reducing undesired afterglow in scintillators.

Низкотемпературная люминесценция и термостимулированная люминесценция монокристаллов BeO : Mg

AbstractLuminescence and thermally stimulated luminescence (TL) of BeO: Mg crystals are studied at T = 6–380 K. The TL glow curves and the spectra of luminescence (1.2–6.5 eV), luminescence excitation, and reflection (3.7–20 eV) are obtained. It is found that the introduction of an isovalent magnesium impurity into BeO leads to the appearance of three new broad luminescence bands at 6.2–6.3, 4.3–4.4, and 1.9–2.6 eV. The first two are attributed to the radiative annihilation of a relaxed near-impurity (Mg) exciton, the excited state of which is formed as a result of energy transfer by free excitons. The impurity VUV and UV bands are compared with those for the intrinsic luminescence of BeO caused by the radiative annihilation of self-trapped excitons (STE) of two kinds: the band at 6.2–6.3 eV of BeO: Mg is compared with the band at 6.7 eV (STE_1) of BeO, and the band at 4.3–4.4 eV is compared with the band at 4.9 eV (STE^2) of BeO. In the visible region, the luminescence spectrum is due to a superposition of intracenter transitions in an impurity complex including a magnesium ion. The manifestation of X-ray-induced luminescence bands at T = 6 K in BeO: Mg indicates their excitation during band-to-band transitions and in recombination processes. The energy characteristics of the impurity states in BeO: Mg are determined; the effect of the isovalent impurity on the fluctuation rearrangement of the BeO: Mg structure in the thermal transformation region of STE_1 → STE_2 is revealed.

Low-temperature luminescence and thermally stimulated luminescence of BeO: Mg single crystals

Luminescence and thermally stimulated luminescence (TL) of BeO: Mg crystals are studied at T = 6–380 K. The TL glow curves and the spectra of luminescence (1.2–6.5 eV), luminescence excitation, and reflection (3.7–20 eV) are obtained. It is found that the introduction of an isovalent magnesium impurity into BeO leads to the appearance of three new broad luminescence bands at 6.2–6.3, 4.3–4.4, and 1.9–2.6 eV. The first two are attributed to the radiative annihilation of a relaxed near-impurity (Mg) exciton, the excited state of which is formed as a result of energy transfer by free excitons. The impurity VUV and UV bands are compared with those for the intrinsic luminescence of BeO caused by the radiative annihilation of self-trapped excitons (STE) of two kinds: the band at 6.2–6.3 eV of BeO: Mg is compared with the band at 6.7 eV (STE1) of BeO, and the band at 4.3–4.4 eV is compared with the band at 4.9 eV (STE2) of BeO. In the visible region, the luminescence spectrum is due to a superposition of intracenter transitions in an impurity complex including a magnesium ion. The manifestation of X-ray-induced luminescence bands at T = 6 K in BeO: Mg indicates their excitation during band-to-band transitions and in recombination processes. The energy characteristics of the impurity states in BeO: Mg are determined; the effect of the isovalent impurity on the fluctuation rearrangement of the BeO: Mg structure in the thermal transformation region of STE1 → STE2 is revealed.

Emission properties of Ce-doped alkaline earth borate glasses for scintillator applications

We investigate the photoluminescence (PL) and X-ray-induced luminescence properties of 0.1 mol% Ce-doped MO-B2O3 (M = Ca, Sr, and Ba) glasses. We also determine the Ce3+/(Ce3++Ce4+) ratio by X-ray absorption near-edge structure analyses. The emission intensities of PL, X-ray scintillation, and thermally stimulated luminescence (TSL) depend on the host glass composition. The order of the PL intensity from highest to lowest is as follows: Ca-substituted glass, Ba-substituted glass, and Sr-substituted glass. Our results suggest that the optical absorption edge and quantum yield (QY) are influenced by the local coordination state of Ce3+, which, in turn, is likely to be affected by the optical basicity. The order of the X-ray scintillation intensity from highest to lowest is reverse of that of the PL intensity. This is probably because the interaction probability of X-rays with matter depends on the effective atomic number of the material and the effective atomic number has a stronger influence on the scintillation intensity than does the QY. Though the TSL glow curves reveal that the density and energy depth of the trap sites depend on the substituted alkaline earth oxides, we are unable to correlate the electron spin resonance (ESR) spectra with the TSL results. Therefore, it is considered that the ESR active sites are not responsible for the TSL in these systems.