Glow Curve Deconvolution Research Articles

Al5BO9:Tb3+: Synthesis, structural characterization and thermoluminescence dosimetry studies for high intensity thermal neutron beams

In this manuscript, gel-combustion synthesis of Al5BO9:xTb3+ (x = 0.0%, 0.05%, 0.1%, 0.2% and 1.5%) phosphor along with the detailed structural characterizations using a host of techniques such as XRD, SEM, EDS, IR, EXAFS and PL etc. has been reported. XRD analysis confirmed the phase pure formation and also the nanocrystalline nature of the materials. Detailed EXAFS analysis explained the oxidation state and the coordination behaviour of Tb3+ ion in the Al5BO9 matrix. PL study showed that the material can be a potential green light emitting phosphor. Thermoluminescence (TL) study revealed the presence of a wide shoulder peak and a broad dosimetry peak situating at 551 K. Net TL response from 10B and 11B enriched Al5BO9:0.1%Tb3+ thin pellets showed prolonged linearity within the thermal neutron fluence range of 3.2 × 1010 to 1.6 × 1011 n/cm2. Also, the maximum fading of the TL signal is only 9% during the storage period of 112 days. These indicates that the developed material can be a potential candidate for dosimetry applications involving high intensity slow neutron beams. The TL glow curve was deconvoluted which revealed the presence of five individual peaks whose kinetic parameters viz. activation energy (E), order of kinetics (b) and frequency factor (s) were evaluated using both glow curve deconvolution and Chen's peak shape method and the results were found to be in good agreement.

Intense green light emission and thermoluminescence glow curve analysis of Tb3+ -activated CaY2 O4 phosphor.

Here, the synthesis and luminescence analysis of the Tb3+ -activated phosphor were reported. The CaY2 O4 phosphors were synthesized using a modified solid-state reaction method with a variable doping concentration of Tb3+ ion (0.1-2.5mol%). As synthesized, the phosphor was characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis techniques for the optimized concentration of doping ions. The prepared phosphor showed a cubic structure, and FTIR analysis confirmed functional group analysis. It was discovered that the intensity of 1.5mol% was higher than at other concentrations after the photoluminescence (PL) excitation and emission spectra were recorded for different concentrations of doping ions. The excitation was monitored at 542 nm, and the emission was monitored at 237 nm. At 237 nm excitation, the emission peaks were found at 620 nm (5 D4 →7 F3 ), 582 nm (5 D4 →7 F4 ), 542 nm (5 D4 →7 F5 ), and 484 nm (5 D4 →7 F6 ). The 1931 CIE (x, y) chromaticity coordinates showed the distribution of the spectral region calculated from the PL emission spectra. The values of (x = 0.34 and y = 0.60) were very close to dark green emission. Therefore, the produced phosphor would be very useful for light-emitting diode (green component) applications. Thermoluminescence glow curve analysis for various concentrations of doping ions and various ultraviolet (UV) exposure times was carried out, and a single broad peak was found at 252°C. The computerized glow curve deconvolution method was used to obtain the related kinetic parameters. The prepared phosphor exhibited an excellent response to UV dose and could be useful for UV ray dosimetry.

Nanostructured TLDs: Studying the impact of crystalline size on the Thermoluminescence glow-curve shape and electron trapping parameters

Nanostructured thermoluminescent dosimeters (TLDs) and their relevance in the field of Stimulated Luminescence has grown over the past years. Particularly, since preparation methods and characterization techniques have been improved, while their integration in technological advancements which has also significantly increased. Despite the numerous case studies dealing with applications and properties of nanomaterials, there is a limited number of studies investigating cases from a basic research point of view, like studying the transition of a material from bulk to nanoscale and the dominant features of this transition. Specifically, in Thermally Stimulated Luminescence or Thermoluminescence (TL), the extensive study via geometrical signal processing with the well-established techniques of Peak Shape Methods (PSM) and Computerized Glow-Curve Deconvolution (CGCD), and the estimation of trapping parameters of certain TL peaks, along with possible dependence of the activation energy of electron traps inside the crystal structure for different crystalline sizes, are missing from the literature. The present study includes several popular TLDs like BeO, LiF, CaSO4 and other more complex crystal structures such as NaLi2PO4, K2Ca2(SO4)3, LiNaSO4 and a geological Fluorapatite in different crystalline size fractions. Special emphasis has been devoted to the estimation of activation energies and the geometrical characteristics in the nanoscale by analyzing each TL signal accordingly. While the analysis imposes several interesting cases on the implementation of the results, the study has shown that under different crystalline sizes, most of materials follow a normal downtrend on their signal with some insignificant alterations on their physical parameters.

Determination of the kinetic parameters of BeO luminescent material using different methods towards X-ray irradiation

In this work, the thermoluminescence (TL) and optically stimulated luminescence (OSL) kinetics of a recently developed beryllium-oxide dosimeter (BeOR) were studied with different methods. The TL and OSL dose responses were also established for an X-ray dose interval of 2–10 Gy. The TL kinetic parameters were determined using three methods, namely: the peak shape (PS), the first-order kinetics (FOK) using Glow-Fit, and the general-order kinetics (GOK) using computerized glow-curve deconvolution (CGCD). TL glow curves of the irradiated BeOR show two distinct TL experimental peaks at ∼250 and ∼379 °C under a heating rate of 5 °C/s. The PS method demonstrates a kinetics order of about two (∼2) for the first peak, whereas the second peak follows first-order kinetics. The activation energies resulting from PS method range from 0.98±0.03 to 1.01±0.05 eV for the first peak and from 1.56±0.07 to 1.58±0.08 for the second peak. The FOK-Glow-Fit show three deconvolution peaks (1.02, 1.05, and 1.07 eV) for the first TL experimental peak and one peak (1.94 eV) for the second experimental peak. The GOK-CGCD method reveals three peaks of ∼1.04, 1.6 (experimental peak1), and ∼2.1 eV (experimental peak2). The TL kinetic parameters were established and compared for the three considered methods. Based on the TL kinetics study, OSL kinetics parameters of BeOR were also determined. The established TL and OSL dose responses of studied dosimeter show linear behaviour that allow effective dosimetry application in photon radiotherapy.

Photoluminescence and thermoluminescence kinetic features of Eu3+ doped Sr2YVO6 double perovskite phosphor

Through traditional high-temperature combustion synthesis, a series of luminescent orange-red emitting Sr2YVO6:Eu3+ double perovskite phosphors were prepared, and their luminescence properties were examined. Through X-ray diffraction (XRD) and Rietveld analysis, the monoclinic crystal structure of all prepared Sr2YVO6:Eu3+ phosphors were confirmed. Scanning electron microscopy (SEM) was used to analyse the morphology of the phosphor. Under 320 nm excitation, Eu3+ doped Sr2YVO6 phosphors exhibit very strong red photoluminescence (PL) emission bands at 595 nm, 616 nm and 620 nm as well as distinct red emission bands at 653 nm and 699 nm, which are originated due to the 5D0-7FJ (J = 1,2,3,4) transition of Eu3+. A series of phosphor also exhibit orange-red emission at 595 nm, 612 nm, 616 nm and 620 nm under the excitation wavelength of 396 nm. High color purity of the phosphors is revealed by calculated color purity and excellent chromaticity coordinates, which also confirms the presence of far-red luminescence emission. After the irradiation of the phosphors at various beta doses via 90Sr/90Y beta source, the thermoluminescence (TL) studies of Eu3+ activated Sr2YVO6 phosphors was conducted. Exposer of beta irradiation revises a prominent TL glow curve at 124 °C with a small hump at around 290 °C, indicating the development of different trap centres in the phosphor. As the dose of beta radiation increased, a linear dose response was observed in TL intensity. Computerised Glow Curve Deconvolution (CGCD) method and Chen's Peak Shape Method (PSM) were used to determine the activation energies and trapping parameters of TL glow curves. According to CGCD fitting of TL glow curves, it is found that all glow curves consist of five deconvoluted peaks, which follows general order kinetics. Activation energies calculated through different methods were comparable and significant.

Thermoluminescence and optically stimulated luminescence properties of NaMgF3:Dy,Eu synthesized by hydrothermal method and DFT calculations for the bandgap

This study indicates Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) radiation dosimetry characteristics for NaMgF3:Dy1%,Eu0.1% fluoroperovskite. Nanocrystalline NaMgF3:Dy1%,Eu0.1% material was synthesized by hydrothermal technique. The structure and optical properties were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG), derivative thermogravimetry (DTG), radioluminescence (RL) and photoluminescence (PL) techniques. The bands on RL spectrum at 365, 488 and 477 nm might be attributed to Eu,2+ Eu3+ and Dy3+ ion emissions, respectively. The experimentally obtained TL glow curve was analyzed by the computerized glow curve deconvolution (CGCD) and various heating rate (VHR) methods and the order of kinetics (b), activation energy (E), and frequency factor (s) were determined for the appeared four peaks of the TL glow curve with 2°C /s heating rate. The energy bandgaps were calculated and the dependence of bandgap on composition was reported through the Density Functional Theory (DFT) computation.

Investigation of kinetic parameters of γ irradiated SrSO4:Eu3+(2%) nanoparticles

SrSO4 nanoparticles doped with Eu3+ (2%) have been synthesized by the co-precipitation method. X-ray diffraction (XRD) confirmed the formation of an orthorhombic crystal structure having crystallite size around 75 nm. The readings of TL glow curves of the samples irradiated with 100 Gy of γ- dose are measured at different heating rates. The TL glow curve has a single peak at 193 °C for a heating rate of 1 K/s, which is favourable for the dosimetric application. The kinetic parameters of the TL glow curves such as activation energy, order of kinetics and frequency factors are evaluated for the synthesised nanoparticles using different methods which values are found to be around 1.41 eV, 1.3 and 1.5 × 1014 s−1 respectively. The values of the kinetic parameters evaluated using different methods are in good agreement. The results are also analogous to the parameters evaluated from the standard glow curve deconvolution method using r-software package “tgcd”.

Double perovskite structured Ca2MgWO6:Sm3+ nanophosphor: Tailored for future-generation WLEDs and dosimetry applications

In fast-growing technologies, the development of innovative materials which can be used in multiple applications to fulfill the present necessary needs is highly motivated. Hence, in the present work, amber red-emitting double perovskite structured Sm3+ ions-doped Ca2MgWO6 nanophosphors were synthesized via the solution combustion route. The structural studies confirm the monoclinic crystal phase of the prepared nanophosphors. The energy band gap of the prepared nanophosphors was estimated and found to be ∼ 3.86 – 3.97 eV. The photoluminescence emission spectra showcase three intense and sharp peaks centered at ∼ 570, 603, and 645 nm, which ascribed to the 4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 transitions of Sm3+ ions, respectively. The photometric properties of the nanophosphors revealed amber-red region emission with ∼ 99.9% of chromatic purity. Thermoluminescence glow curves of the synthesized nanophosphors after irradiation of 10 KGy doses of γ-rays exhibit clear distinctive peaks at ∼ 140, 232, and 264 °C, which ascribed to increased luminescent trapping levels and defect population. The thermoluminescence linear response of the Ca2MgWO6:Sm3+ (3 mol%) nanophosphors within a wide range of 0.1–10 KGy of γ- ray doses are noticed. The various kinetic and trapping parameters were estimated via the computerized glow curve deconvolution method. The aforementioned results revealed that the prepared nanophosphors can be used for both future-generation white light-emitting diodes and dosimetry applications.

Electronic structure and defects induced luminescence study of phase stabilized t-ZrO2 nanocrystals.

Luminescent tetragonal-ZrO2 nanocrystals were synthesized using an optimized combustion method without post-synthesis annealing and characterized using X-ray diffraction, electron microscopy, Raman, X-ray photoelectron spectroscopy, UV-Visible, photoluminescence spectroscopy, thermoluminescence and vibrating sample magnetometry. The as synthesized t-ZrO2 nanocrystals have a band gap of 4.65 eV and exhibit defect assisted blue emission (CIE coordinates 0.2294,0.1984) when excited with 270 nm. The defect states were qualitatively and quantitatively analyzed using thermoluminescence (TL) after irradiating nanocrystals with gamma and UV radiation at various doses. The TL glow curves show intense emission in the high temperature region from 523-673 K for both UV and gamma irradiated samples; however, another less intense TL peak was also observed in the low temperature region from 333-453 K with gamma irradiation at higher doses, indicating the formation of shallow trapping states. The activation energies, frequency factor and order of kinetics were estimated through the computerized glow curve deconvolution method for the shallow and deep traps for γ and UV- irradiated samples. The present study shows that phase stabilized t-ZrO2 nanocrystals are potential candidates for luminescence-based applications.

Thermoluminescence in GdAl3(BO3)4 phosphors: Unusual heating rate dependencies, dose responses and kinetic parameters

The current study focuses on the production of GdAl3(BO3)4 (GAB) phosphors using gel combustion. X-ray diffraction (XRD) and thermoluminescent (TL) methods were used to investigate the structural and thermoluminescence (TL) features of the samples. XRD results revealed that GAB phosphors were crystallized in a rhombohedral crystal system. TL experimental data exhibited an unusual heating rate behaviour, which was explained by the semi-localized transition model, and this provides valuable insight into the properties of the GAB sample. Beta-irradiated GAB hosts exhibit two primary peaks at 106 °C and 277 °C on their TL glow curves. We have employed a variety of heating rates (VHRs), TM-Tstop method, and computerized glow curve deconvolution (CGCD) techniques. By using a combination of these techniques, we can identify the kinetic parameters of the GAB samples more accurately, including peak numbers, activation energy, and frequency factors. Both Tm-Tstop and CGCD techniques produce similar results in terms of trap numbers and trap depths. In the trap centers, electrons were trapped at 1.05 eV, 0.84 eV, 1.12 eV, 1.20 eV, 1.42 eV, 1.63 eV and 1.42 eV. There was a linear behaviour of GAB samples over a dose range of 0.1 Gy–10 Gy. GAB phosphors did not show any significant changes in TL response with repeated irradiation cycles, suggesting that it is a reliable radiation dosimeter. GAB is therefore a potential candidate for radiotherapy dose measurement based on these findings.

Thermoluminescence dosimetric and kinetic characterization of Pakistani fluorite after β irradiation

The thermoluminescence (TL) characteristics of seven fluorite mineral samples from Pakistan have been investigated for the first time. The TL glow curve structure of different colors of fluorite were thoroughly studied for their potential use in dosimetric applications. Light green (LG) fluorite was found the most sensitive and promising one. Therefore, light green (LG) fluorite was further investigated in detail as TL dosimeter. First, the crystallinity, microstructural properties, and potential impurities present in the LG sample were identified using x-ray powder diffraction (XRD), Scanning electron microscopy (SEM-EDX), and inductively coupled plasma (CP) techniques respectively. The β-irradiated powder sample showed that this fluorite has a complex glow curve structure with five prominent peaks at about 75, 100, 163, 251, and 358 °C in the temperature range of 40 to 400 °C. In the low β dose range of 80 mGy to 5120 mGy, the sample dose response was linear with a minimum detectable dose of 9.7 mGy. Taking the peak specific dose responses, the peak around 251 °C (R2 = 1) was found most suitable for dosimetric applications. A progressive decrease is observed in the response which reached to about 4% after 10 cycles of irradiation, readout and annealing with less than 1% coefficient of variation (COV). After one week, the TL signal faded by approximately 8%; however, after one month of storage, the signal returned to near-stable level. A newly designed deconvolution program was used for the analysis of the TL kinetics. The kinetic parameters like activation energy (E), frequency factor (s), the order of kinetics (b), and the trap lifetimes were investigated. The values found using additive dose (AD), Tm -Tstop, various heating rate (VHR) and computerized glow curve deconvolution (CGCD) methods were in close proximity. The study concludes that light green fluorite from Pakistan can be used as a potential candidate for thermoluminescence dosimetry (TLD) applications.

Kinetic parameters and luminescence properties of rare earth (Tb, Nd) doped and transition metal (Mn) doped/co-doped YAlO3 prepared via sol-gel method

In this work, phosphor materials with the formula YAlO3 were synthesized via sol-gel method by using the stoichiometric amounts of yttrium nitrate and aluminum nitrate as base materials. The obtained phosphors were doped/co-doped with Tb3+, Nd3+ rare earth ions and Mn2+ transition metal ion. For evaluating the influence of the dopants, the grain size and morphology of the samples by scanning electron microscopy (SEM) and the phase and crystallinity of the synthesized materials by X-ray diffraction (XRD) were investigated. Optical absorption spectra, photoluminescence (PL) and thermoluminescence (TL) were performed to determine a relationship the changing dopant on luminescence properties of YAlO3. Moreover, the kinetic parameters namely activation energy (E), order of kinetics (b) and frequency factor (s) of the synthesized pure and doped materials were calculated using Computerized Glow Curve Deconvolution (CGCD) and Peak Shape Method for a better understanding of the optical properties that change with the doping process. Strong green emission was detected in the sample doped with Mn2+ correspond to 4T1(G)→6A1(S) transition. As for YAlO3: Nd3+, characteristic emissions originated from 4G11/2 → 4I9/2 (∼423 nm), 4G9/2 → 4I9/2 (∼460 nm) and 4G7/2 → 4I9/2 (∼540 nm) transitions were seen. The optical band gap of undoped sample was calculated as 2.79 eV and depending on the presence of Nd3+ and Tb3+ dopant ions this value was decreased to the range 2.46–2.56 eV.

Thermoluminescence kinetic parameters of beta irradiated the zinc gallate phosphor using different methods

The ZnGa2O4 phosphor material was synthesised through the gel combustion method, and its structural characteristics were studied via X-ray powder diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). The XRD result indicates the generation of ZnGa2O4 in spinal cubic phase with a 25 nm crystalline size. The synthesized phosphor was irradiated using a90Sr/90Y source with a dose range of 0.1 Gy–100 Gy. For measuring thermoluminescence (TL), a linear heating rate of 2 °Cs−1 was applied to the sample in a temperature range of 25 °C–450 °C. The TL experiment revealed two peak maxima located at 180 °C and 304 °C and a shoulder around 70 °C. By preheating at 110 °C, the low temperature peak at 70 °C is removed. Both the depth and frequency factors of electron traps were determined using various heating rates (VHR), Tm-Tstop combined with initial rise (IR), and Computerised Glow Curve Deconvolution (CGCD). In both the Tm-Tstop and CGCD methods, six overlapping glow peaks were detected below the main glow peaks. The calculated activation energy values and peak maximum temperatures agree well with each other. The depths of electron traps calculated by different methods were found to be between 0.4 and 1.4 eV. We observed that both peak maximum temperatures and the area under glow peaks gradually decreased with an increase in the heating rate. Both Peak 1 and Peak 2 show sublinear relationship between 0.1-5Gy and 10–100 Gy. The findings of the present study show that the phosphors can serve as effective TLDs.

Study of the thermoluminescence properties of γ and UV-C irradiated Li3PO4: Dy synthesized by solid state diffusion method

This paper reports the thermoluminescence (TL) properties of Li3PO4 doped with rare earth Dy3+ ions. The solid state diffusion method is used to synthesize phosphors with varying concentrations of the dopant (0.1, 0.2, 0.3, 0.4 and 0.5 mol%). Characterization of the samples is performed using X-ray diffraction (XRD), Fourier Transform Infrared-Attenuated Total Reflection spectroscopy (FTIR-ATR) and Scanning Electron Microscopy (SEM). Samples are irradiated with γ rays in the dose range of 10 Gy to 6 kGy and by UV-C rays (254 nm) for exposure duration ranging from 0.5 to 5 h. Maximum TL intensity in both cases is observed for the phosphor doped with 0.2 mol% Dy3+. While a linear TL response is found for the entire duration of UV-C irradiation, the dose response for γ irradiation stays linear upto 3 kGy for the high temperature peak at 335∘C. Appreciable repeatability values are found (for both γ and UV-C irradiated samples) and significantly low fading (for the UV-C irradiated phosphor) is reported. The computerized glow curve deconvolution has been done using an R-package, “tgcd: Thermoluminescence Glow Curve Deconvolution” by assuming the Kitis general order kinetics model. Chen’s peak shape method is utilized to extract trapping parameters such as the order of kinetics (b), shape factor (μg), frequency factor (s), activation energy (E) and trap density (n0). Various promising properties of this material are found suggesting that it could be used as a TL dosimeter.

Green synthesis of MgO nanoparticles and its antibacterial properties.

Magnesium oxide nanostructured particles (NP) were prepared using a simple solution combustion technique using different leaf extracts such as Mangifera indica (Mango - Ma), Azadirachta indica (Neem-Ne), and Carica papaya (Papaya-Pa) as surfactants. The highly crystalline phase of MgO nanostructures was confirmed by PXRD and FTIR studies for 2h 500°C calcined samples. To analyze the characteristics of obtained material-MaNP, NeNP, and PaNP for dosimetry applications, thermoluminescence (TL) studies were carried out for Co-60 gamma rays irradiated samples in the dose range 10-50KGy; PaNP and NeNP exhibited well-defined glow curve when compared with MaNP samples. In addition, it was observed that the TL intensity decreases, with increase in gamma dose and the glow peak temperature is shifted towards the higher temperature with the increase in heating rate. The glow peak was segregated using glow curve deconvolution and thermal cleaning method. Kinetic parameters estimated using Chen's method, trap depth (E), and frequency factor (s) were found to be 0.699, 7.408, 0.4929, and 38.71, 11.008, and 10.71 for PaNP, NeNP, and MaNP respectively. The well-resolved glow curve, good linear behavior in the dose range of 10-50, KGy, and less fading were observed in PaNP as compared with MaNP and NeNP. Further, the antibacterial activity was checked against human pathogens such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. A visible zone of clearance was observed at 200 and 100μg/mL by the PaNP and NeNP, indicating the death of colonies by the nanoparticles. Therefore, PaNP nanomaterial is a potential phosphor material for dosimetry and antibacterial application compared to NeNP and MaNP.

Comparing the effect of electron beam, beta and ultraviolet C exposure on the luminescence emission of commercial dosimeters

This paper reports on the luminescence characterization of TLD-100 (LiF: Ti, Mg), TLD-200 (CaF2: Dy), TLD-400 (CaF2: Mn) and GR-200 (LiF: Mg, Cu, P) dosimeters exposed to electro beam, beta and ultraviolet C radiation -UVC-. All of them show high sensitivity to radiation regardless of whether it is ionizing or partially ionizing radiation based on their luminescence properties (cathodoluminescence -CL- or thermoluminescence -TL-). CL emission differs significantly among them in shape and intensity due to their chemical compositions. LiF samples display three maxima at: (i) 300–450 nm linked to intrinsic and structural defects, (ii) a green waveband probably due to F3+ centres or the presence of hydroxyl groups and (iii) the red-infrared emission band associated with F2 centres. However, CL spectra from the CaF2 dosimeters display meaningful differences due to the dopant. TLD-200 is characterized by an emission with four sharp individual peaks in the green-IR spectral region (due to the Dy3+), whilst TLD-400 exhibits a broad maximum peaked at ̴500 nm (linked to the Mn2+). On the other hand, the variation in the TL glow curves allows to discriminate the TLDs exposed to beta and UVC radiation since they give rise to different chemical-physical processes and that have been studied from the estimation of the kinetic parameters by means of the Computerised Glow Curve Deconvolution (CGCD) method.

Thermoluminescence characterization of natural and synthetic irradiated Ce-monazites

The thermoluminescence (TL) emission of synthetic and natural Ce-monazites was characterized here to determine the potential application in the identification of microscopic defects from a qualitative point of view trying to link each TL peak to a chemical-physical process. The kinetic parameters that lead the luminescence processes were calculated by means of variable heating rate and computing glow curve deconvolution methods and allow identifying three groups of components at ∼90, 130 and 290 °C (for the mineral sample) and ∼90, 170, 220, 270 and 320 °C (for the synthetic CePO4:Nd0.20,La0.25). The main differences appreciated in these complex TL curves are mainly due to (i) the content of impurities (natural sample contains lanthanides as well as U 0.60% and Th 5.22%) and (ii) the degree of crystallinity of the samples which is directly related to the type of impurities (synthetic monazite relies only on Nd and La). The behavior of the dose response in the range of 1–8 Gy is similar for both samples; the TL intensity increases linearly as the dose increases without changes in the position of the maxima, denoting first-order kinetic luminescence mechanism. Each peak could be mostly associated with structural defects (i.e., phase transitions), chemical reactions (i.e., Ce3+⇆Ce4+ redox reaction, dehydration or dehydroxylation processes) or intrinsic defects (i.e., Frenkel defects, ODCs or NBOHCs).

Europium doped Sr2 YNbO6 double perovskite phosphor for photoluminescence and thermoluminescence properties.

A luminescent double perovskite phosphor Sr2 YNbO6 doped with Eu3+ crystallized to the monoclinic phase and was synthesized successfully via a conventional high-temperature combustion method. The formation of the crystal structure, phase purity, and surface morphology were studied using X-ray diffraction patterns and scanning electron microscopy. The characteristic vibrations between the atoms of the functional groups present in phosphor were studied using Fourier transform infrared spectra analysis. The luminescence properties of the prepared phosphors were investigated in terms of photoluminescence (PL) and thermoluminescence (TL). PL excitation spectra exhibited charge transfer bands and the characteristic 4f6 transitions of Eu3+ . A prominent PL emission was obtained for the phosphor doped with 4 mol% Eu3+ under the 396 nm excitation wavelength. PL emission quenching was observed for the higher doping concentrations due to a multipole-multipole interaction. A highly intense PL emission arose due to the hypersensitive 5 D0 -7 F2 electric dipole transition of Eu3+ that dominated the emission spectra. The thermal stability of the phosphor was examined through temperature-dependent PL. The TL properties of the Sr2 YNbO6 double perovskites irradiated with a 90 Sr beta source at different doses were measured. The double perovskite phosphors under study showed a linear dose-response with increasing beta dose, ranging from 1 Gy to 10 Gy. Trapping parameters of the TL glow curves were determined using Chen's peak shape method and computerized glow curve deconvolution (CGCD). CGCD fitting of the TL glow curves revealed that it was consisted of three major peaks and followed second-order kinetics. The estimated activation energies were determined using different methods and were comparable and significant.

Structural, thermoluminescence and optical properties of Nd3+ doped Y2O3 nanophosphor for dosimeter and optoelectronics applications

For potential gamma ray dosimetry and near-infrared laser material applications, solution combustion synthesis was used to create undoped and trivalent neodymium doped Y2O3. X-ray powder diffraction was used to analyze the annealed materials. It was discovered that they had a cubic Y2O3 single phase structure up to a dopant level of 2 mol%. The higher dopant concentrations showed the existence of a Nd2O3 solid solution. The crystallite sizes were determined using Scherrer and Williamson-Hall equations and were found to decrease with dopant content. Characterization of the nanocrystals by X-ray photoelectron spectroscopy confirmed excellent stoichiometric control. The γ-ray irradiated phosphors showed a thermoluminescence (TL) peak at about 394 K that sub linearly increased in intensity up to 7 kGy and thereafter decreased. A computerized glow curve deconvolution algorithm was used to analyze the measured complex TL glow curves produced for the phosphors exposed to γ-rays. The 60Co γ-ray irradiated Nd3+ doped Y2O3 sample exhibited peaks at 395, 445, 496 and 596 K with the corresponding activation energies in the range of 1.20-1.32 eV. These were attributed to the F, F+ and V-centers. The main absorption bands, i.e., at 590 and 812 nm for the Nd:Y2O3 nanocrystals. As the host's Nd3+ content increased, the optical band gap decreased. Three major emission bands at wavelengths of 871–957, 1045–1137, and 1306–1379 nm were associated with Nd3+ transitions of 4F3/2→4I9/3, 4F3/2→4I11/3 and 4F3/2→4I13/3, According to calculations, the 4F3/2 energy level's PL lifespan for Nd3+ doped Y2O3was between 68 and 247 µs.

Optimizing the luminescence efficiency of an europium (Eu3+) doped SrY2O4 phosphor for flexible display and lighting applications.

This research paper reports the synthesis and luminescence study of an Eu3+ activated SrY2O4 phosphor prepared by a modified solid-state reaction method with varying concentrations of Eu3+ ions (0.1-2.5 mol%). X-ray diffraction (XRD) revealed the orthorhombic structure and Fourier transform infrared spectroscopy (FTIR) methods were used to analyse the produced phosphors. Photoluminescence emission and excitation spectra were recorded for varying concentrations of Eu3+ ions, and an optimum concentration of 2.0 mol% was found to produce the highest intensity. Under 254 nm excitation the emission peaks were found to be at 580 nm, 590 nm, 611 nm and 619 nm, corresponding to transitions at 5D0 → 7F0, 5D0 → 7F1, and 5D0 → 7F2 respectively. Because of Eu3+ inherent luminosity, these emission peaks indicate radiative transitions between excited states of ions, making them useful for developing white light-emitting phosphors for optoelectronic and flexible display applications. The 1931 CIE (x, y) chromaticity coordinates were calculated from the photoluminescence emission spectra and found to be near white light emission, indicating the potential application of the prepared phosphor for light emitting diodes (white component). TL glow curve analysis was also performed for various concentrations of doping ions and UV exposure times, and a single broad peak was observed at 187 °C. Using the computerised glow curve deconvolution (CGCD) method, kinetic parameters were computed.