Tb Phosphor Research Articles

Synthesis and investigation of the optical characteristics of RE3+ activated Ca2Li2Si2O7 (Rare earth = Eu, Tb) phosphor for W-LED application

Novel Eu3+ and Tb3+ ions-doped Ca2Li2Si2O7 luminescent materials were prepared by a low-temperature solid-state reaction technique for LED application. The electronic transitions of 5D0 → 7F2 (Eu3+) and 5D4 → 7F5 (Tb3+) have caused the luminescent material to exhibit strong luminosity in 613 nm (red) and 545 nm (green), respectively. Fourier transform infrared (FT-IR) spectra were applied for the identification of functional groups, and powder X-ray diffraction (XRD) was used for structural analysis. Morphological data was gathered using scanning electron microscopy (SEM). Its color was also determined by calculating the CIE coordinates. The excitation, PL properties, and luminescence decay time of the emission transitions of Eu3+ (5D0 → 7F2) and Tb3+ (5D4 → 7F5) were measured in order to analyze luminosity spectra.

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

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

Exploring the luminescence properties and dosimetric characteristics of CaSO4:Tb, CaSO4:Mn, and CaSO4:Mn,Tb phosphors synthesized by slow evaporation route

This work aimed to investigate and compare the luminescence properties of CaSO4:Tb, CaSO4:Mn, and CaSO4:Mn,Tb synthesized by slow evaporation route. The crystalline structure, morphology, and optical properties of the phosphors were characterized by X-ray diffraction analysis (XRD), photoluminescence (PL), radioluminescence (RL), and scanning electron microscopy (SEM). In addition, thermoluminescence (TL) and optically stimulated luminescence (OSL) were used to comprehensively investigate the dosimetric properties of the phosphors, such as the TL glow curve and continuous wave OSL (CW-OSL) curves, dose-response and its reproducibility, fading, and sensitivity. For dosimetric analyses, the samples were irradiated with beta radiation. PL and RL emission spectra confirmed the presence of Tb3+ and Mn2+ ions in crystalline matrices. The samples showed a typical exponential OSL decay curve, indicating that the charge traps have a high photoionization cross-section for blue LEDs. The synthesized pellets exhibited good luminescent and dosimetric properties, with linear luminescent response over a wide dose range (169 mGy–100 Gy) and reproducibility of both OSL and TL signals. Furthermore, the incorporation of terbium as a co-dopant in the CaSO4:Mn matrix reduced its fading from 75% to only 17%. The phosphors had high TL and OSL sensitivities in comparison to some commercially available dosimeters.

Thermoluminescence response of carbon ion beam irradiated LiCaAlF6: Tb phosphor

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

Achieving high-efficiency green NaYSiO4:Tb phosphors by optimizing host structure through cation doping

Rare earth activated color converted phosphors have been widely used in solid-state lighting and display fields. Developing phosphors with high luminous efficiency is of great significance for light-emitting devices. Concentration quenching is the main factor limiting the improvement of phosphor luminescence efficiency during increasing the activator doping level. In this study, a novel structural optimization strategy is developed to overcome the impact of concentration quenching. In Tb3+ activated NaYSiO4 (NYSO), large-size Gd3+ ions are introduced to adjust the distance of rare earth ions and suppress the energy transfer between Tb3+ luminescent centers. It is shown that at a critical Tb3+ concentration, for which concentration quenching tends to occur in NaYSiO4:Tb3+, Gd3+ incorporation successfully raises the internal quantum efficiency from 64.8 % for Tb3+-singly-doped NYSO up to 80.6 % for Gd3+/Tb3+ co-doped one. The findings can offer a feasible pathway in promoting the luminescent properties of silicate phosphor hosts.

Dynamic photoluminescent and photochromic properties of CaAl12O19:Eu, Tb: A novel phosphor for advanced dual-modal multicolor anticounterfeiting

The integration of dynamic photoluminescence and photochromism to achieve dual-modal characteristics can substantially elevate the security of anticounterfeiting measures. In this study, a novel bifunctional phosphor, namely CaAl12O19:Eu, Tb possessing dynamic photoluminescence and photochromism, is developed by the sol-gel combustion method. As the duration of exposure to 254 nm ultraviolet radiation increases, the CaAl12O19:Eu, Tb phosphors exhibit exceptional dynamic luminescent characteristics and pronounced color changes. Furthermore, this exposure results in a photochromic phenomenon on the surface of the samples, causing a shift from white to light brown. With an increase in Tb doping concentration, distinct and diverse chromatic variations easily discernible are observed by the naked eye. In addition, the mechanisms underlying the dynamic photoluminescent and photochromic characteristics are analyzed herein. Furthermore, the application of the bifunctional phosphor CaAl12O19:Eu, Tb for advanced dual-modal multicolor anticounterfeiting is explored, offering enhanced security against duplication attempts.

Anomalous dose behaviour of thermoluminescence glow curves and kinetic analysis of beta irradiated YAl3(BO3)4:Tb phosphor

With the aid of thermoluminescence (TL), we have extensively studied YAl3(BO3)4 host matrices incorporated with Tb3+ at different doping contents, which have been produced by combustion. The measured the TL glow curves exposed to beta rays at different doses consisted of four broad peaks located at around 76, 126, 230, and 378 °C. The peak maximum of the 230 °C TL peak shifts toward higher temperatures after 5 Gy beta irradiation while the other peak maxima almost remain constant. It is peculiar that 230 °C peak maximum shifts to higher temperatures with increased radiation dose and can be attributed to the multiple phases of the sample. A TL glow curve exhibits a proportional increase in intensity with increased the heating rate. A discussion of the possible causes of this pattern is provided. Observed peaks using the Tm─Tstop method are due to the presence of a quasi-continuous distribution of traps. The parameters of the traps have also been estimated using various heating rate methods in excellent agreement with one another.

Особенности изменения интенсивностей основных полос фотолюминесценции ионов Tb-=SUP=-3+-=/SUP=- и их сателлитов в поликристаллическом люминофоре Gd-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-:Tb(3 mol%)

Samples of Gd2O3:Tb(3 mol%) phosphor were obtained by sol-gel method followed by annealing at 800oC and 1200oC in air. At high annealing temperature, the intensities of the main emission bands 484 and 541 nm increase, but the ratio of the intensities of these emission bands to their satellites 493 and 549 nm respectively decreases. Based on the analysis of X-ray diffractometry, radiation spectra, far-infrared and Raman spectroscopy, as well as diffuse reflectance spectroscopy, we established: the increase in the crystallinity of the samples with a significant reduction of the lattice strain stress at elevated annealing temperatures, changes in the structure of the bandgap with degenerated acceptor and donor zones of impurities Tb4+ and Tb3+ respectively. The diffuse reflection spectra of the sample after annealing at 800oC under optical excitation showed a direct charge transition through the bandgap with Eg = 2.56 eV. After elevated annealing temperature the concentration of Tb4+ ions decreases due to reduction to Tb3+. As a result, at low excitation energies the degeneracy of the acceptor zone is still preserved and there is a direct transition of charges through the bandgap with Eg = 2.55 eV. At high excitation energies the degeneracy of the acceptor zone is removed and there is a direct transition through the bandgap with Eg = 3.39 eV. These effects are accompanied by a relatively large increase in the emission intensity of the satellites, especially at the 549 nm.

Structure and luminescence properties of single-component melilite Sr2MgSi2O7:Ce/Tb/Sm for n-UV wLEDs.

Phosphor-converted white light-emitting diodes (pc-wLEDs) have attracted attention in the field of solid-state lighting. Selection and study of suitable single-phase phosphor and packaging modes are currently the main research hotspots. Herein, color-tunable photoluminescence (PL) and thermally stable tri-doped Melitite Sr2MgSi2O7:Ce/Tb/Sm are systematically studied via structural and static/dynamic spectral analyses. All dopants could only be accommodated in the Sr site due to similar ionic radii. Previous studies have concluded that green and red PL could be obtained from singly doped Tb and Sm phosphors with excellent reproduction, and color tunable PL can be achieved from Ce/Tb co-doped phosphors. The forbidden 4f-4f transitions of Tb/Sm cause low efficiency and Ce/Tb co-doping cannot achieve white light emissions. Alternatively, co-doping allowed 5d-4f transition sensitizer with emissions in the UV-blue region (i.e., Ce), color-tunable PL (including the white light); high efficiency of Sr2MgSi2O7:Ce/Tb/Sm could be achieved via energy transfer (ET) from Ce → Tb → Sm. The impossibly direct ET from Ce → Sm is associated with the side metal-metal charge transfer (MMCT) effect. Due to chemically nonequivalent substitutions, two positive Ce(Tb,Sm)Sr and one negative V''Sr were created to maintain the whole charge balance. To reduce the defects and allow more dopants to enter into the Sr site, Na+ was added as a charge balancer to enhance PL efficiency. Furthermore, an alkaline-earth-metal-ions blending strategy via partial replacement of Sr with Ba was investigated to regulate PL owing to the change in crystal field splitting. PL blue-shifted by Ba-co-doping, which could increase the degree of overlapping and enhance ET efficiency. As a proof-of-concept experiment, the pc-wLED fabricated via a combination of the optimal Sr(Ba)2MgSi2O7:Ce/Tb/Sm/Na and an n-UV LED chip based on a remote 'capping' packaging mode shows excellent performances, indicating its strong potential application in the field of solid-state lighting.

Peculiarities of changes in the intensities of the main photoluminescence bands of Tb-=SUP=-3+-=/SUP=- ions and their satellites in polycrystalline Gd-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- : Tb(3 mol%)

Samples of Gd2O3 : Tb(3 mol%) phosphor were obtained by sol-gel method followed by annealing at 800oC and 1200oC in air. At high annealing temperature, the intensities of the main emission bands 484 and 541 nm increase, but the ratio of the intensities of these emission bands to their satellites 493 and 549 nm respectively decreases. Based on the analysis of X-ray diffractometry, emission spectra, far-infrared and Raman spectroscopy, as well as diffuse reflectance spectroscopy, we established: the increase in the crystallinity of the samples with a significant reduction of the lattice strain stress at elevated annealing temperatures, changes in the structure of the bandgap with degenerated acceptor and donor zones of impurities Tb4+ and Tb3+ respectively. The diffuse reflection spectra of the sample after annealing at 800oC under optical excitation showed a direct charge transition through the bandgap with Eg=2.56 eV. After elevated annealing temperature the concentration of Tb4+ ions decreases due to reduction to Tb3+. As a result, at low excitation energies the degeneracy of the acceptor zone is still preserved and there is a direct transition of charges through the bandgap with Eg=2.55 eV. At high excitation energies the degeneracy of the acceptor zone is removed and there is a direct transition through the bandgap with Eg=3.39 eV. These effects are accompanied by a relatively large increase in the emission intensity of the satellites, especially at the 549 nm. Keywords: Gd oxide, Tb3++ photoluminescence spectra, far infrared and Raman spectroscopy spectra, structure of the bandgape, distribution of Tb3+ and Tb4+ in cation sublattice.

Luminescence and Energy Transfer of Li2Y4(MoO4)7:Ln (Ln = Dy, Tb) Phosphors

Luminescence and Energy Transfer of Li2Y4(MoO4)7:Ln (Ln = Dy, Tb) Phosphors

Impact of Tb doping on luminescence properties of LiCaAlF6 phosphor prepared in argon atmosphere and charge transfer mechanism

This work focuses on the synthesis and characterization of Tb doped LiCaAlF6 phosphor for its OSL dosimetry properties. The phosphor has been prepared by melting method. XRD shows the formation of LiCaAlF6 with enrichment of CaF2. The excess availability of Ca2+ions are advantageous in incorporation of Tb dopant. The photoluminescence studies show the increase in the luminescence intensity after Tb doping by showing strong emission corresponding to 5D4 → 7FJ (J = 6, 5, 4, 3) transitions with a prominent green emission transition 5D4 → 7F5 at 540 nm. Further, Tb ion exist in Tb3+ and Tb4+ state as observed from XPS. The incorporation of Tb4+ ion is difficult to achieve and its presence in the host might also increase the of number of trapping states. The OSL studies of LiCaAlF6: Tb show high intensity under blue light stimulation for beta irradiation in the dose range 0.05–10Gy. The OSL sensitivity of LiCaAlF6: Tb phosphor is found to be ∼8 times higher to that of commercially available Al2O3: C. The phosphor has shown dose linearity in the range of 0.05–10Gy and minimum detectable dose (MDD)∼6.95 μGy. The enhanced sensitivity may be attributed to the additional defect centers due to excess CaF2 with mixed oxidation state of Tb3+ and Tb4+ ions. The enhancement of OSL signal of LiCaAlF6: Tb in comparison to Al2O3:C has been discussed based on charge compensation mechanism. These results indicate that LiCaAlF6: Tb phosphor prepared via melting method in Ar gas atmosphere shows good OSL properties and has potential application in radiation dosimetry.

Sol-gel synthesis of CaYAlO4:Tb phosphors and their application in detecting nitroaromatic compounds

• CaYAlO 4 :Tb was synthesized by a citrate acid assisted Pechini sol gel approach. • CaYAlO 4 :Tb emits stable red emission under irradiation of ultraviolet in different conditions. • CaYAlO 4 :Tb are good fluorescent probe of p -NT, 1,2-DNT and 4-NT. • The quenching mechanism is of a dynamic quenching one based on inner filter effect. Nitroaromatic compounds are highly toxic, carcinogenic, explosive, and refractory, they do great harm to human health, national security and natural ecosystem, so detecting trace amount of nitroaromatic compounds with high accuracy is crucial to the effective emission control and pollutant treatment. Herein, we synthesized CaYAlO 4 :Tb phosphors by citric acid assisted Pechini sol–gel approach. The samples were characterized by X-ray diffraction (XRD) Fourier transformation infrared (FTIR) spectroscopy, scanning electronic microscopy (SEM), laser particle analyzer, and photoluminescence (PL). The structure and morphology characterizations indicate the samples well crystallize with a K 2 NiF 4 structured CaYAlO 4 at 1100 °C and the samples show irregular morphology with smooth surface and a grain size of about 300 nm. Under irradiation of ultraviolet, CaYAlO 4 :Tb shows the characteristic emission of Tb(III), dominated by the 5 D 4 - 7 F 5 emission at 548 nm. The emission of CaYAlO 4 :Tb can be selectively quenched by nitroaromatic compounds such as p -nitrophenol, 1,2-dinitrobeneze and 4-nitrotoluene. The quenching effect (I 0 /I) can be well fitted into a linear equation, which make CaYAlO 4 :Tb an excellent candidate to detect nitroaromatic compounds. The quenching mechanism is determined to be a dynamic quenching process.

The effect of the grain size distribution (GSD) on the light emission performance of phosphor-based X-ray detectors

The light emission performance of indirect, phosphor-based, X-ray detectors has significantly affected image quality and diagnostic validity of the medical imaging examinations. This issue has been investigated by examining and further understanding the optical anisotropy in optical diffusion mechanisms. One crucial parameter of phosphor's structural properties that remarkably changes light distribution is the size of the phosphor particles. Up to now, the vast majority of studies have been carried out considering phosphor materials consisted of grains of equal size. In the present article an attempt is made to investigate the influence of grain size distribution (GSD) on light emitting characteristics and compare it with the condition of mean values assumptions. Our investigation was based on LIGHTAWE Monte Carlo simulation code with purpose to examine the Gd2O2S:Tb phosphor layer extracted from a mammographic Kodak Min-R 2 Cassette. The GSD was determined via scanning electron microscopy (SEM). Three cases of mean values were taken into account: (i) 1.48 μm obtained calculations of the aforementioned GSD, (ii) 2.50 μm and 7.00 μm taken from previous articles and manufacturer datasheets. Light emission was performed under different irradiation conditions (i. e., light quanta are produced by light source or an X-ray beam) and in terms of light amount and distribution. Our investigation showed that the optical distribution in real GSD was found: (a) sharper than the calculated mean value of the GSD and (b) broader than the mean value taken from the manufacturer datasheet. In particular, the deviation of GSD was found significantly high compared to 7.00 μm mean value. Examining the spatial resolution properties of both conditions, the deviation was around 16.5%, 18.2%, 14.8% assuming that the light source is situated within the phosphor mass, an X-ray beam of 20 keV and X-ray beam of 30 keV, respectively.

Thermoluminescence dosimetric characteristics of terbium doped barium metaborate phosphors

Rare earth doped barium metaborate (BaB2O4) polycrystalline phosphors were synthesized by the solid-state method. Among these, the BaB2O4:Tb phosphor showed a favorable thermoluminescence (TL) glow curve with good sensitivity. TL dosimetric characteristics were studied for BaB2O4:Tb by optimizing the concentration of the Tb dopant at 0.45 mol%. The powder XRD results confirm the formation of stable crystalline material with rhombohedral structure. The TL glow curve of gamma irradiated powder samples revealed two major peaks at 485 K and 620 K. The gamma dose response of this phosphor has been studied from 200 mGy to 20 kGy. For the 485 K peak, the response is found to be linear up to 1 Gy, then there is a supralinearity up to 250 Gy followed by a sublinear response with a linearity index varying from 1 to 1.4 (max.) and finally reducing to 0.9. The TL kinetic parameters such as the activation energy (E), frequency factor (s), and order of the kinetics have been obtained by initial rise, peak shape, and glow curve deconvolution methods. The order of the kinetics for the TL peak has been found to be 2.25 for 485 K and 2 for 620 K. The dosimetric studies showed that BaB2O4:Tb is suitable for dose measurements in high radiation areas, like glove box, hot cells, gamma irradiators etc., except for low energy gammas and x-rays.

Frequency-dependent optimal weighting approach for megavoltage multilayer imagers

Multi-layer imaging (MLI) devices improve the detective quantum efficiency (DQE) while maintaining the spatial resolution of conventional mega-voltage (MV) x-ray detectors for applications in radiotherapy. To date, only MLIs with identical detector layers have been explored. However, it may be possible to instead use different scintillation materials in each layer to improve the final image quality. To this end, we developed and validated a method for optimally combining the individual images from each layer of MLI devices that are built with heterogeneous layers. Two configurations were modeled within the GATE Monte Carlo package by stacking different layers of a terbium doped gadolinium oxysulfide Gd2O2S:Tb (GOS) phosphor and a LKH-5 glass scintillator. Detector response was characterized in terms of the modulation transfer function (MTF), normalized noise power spectrum (NNPS) and DQE. Spatial frequency-dependent weighting factors were then analytically derived for each layer such that the total DQE of the summed combination image would be maximized across all spatial modes. The final image is obtained as the weighted sum of the sub-images from each layer. Optimal weighting factors that maximize the DQE were found to be the quotient of MTF and NNPS of each layer in the heterogeneous MLI detector. Results validated the improvement of the DQE across the entire frequency domain. For the LKH-5 slab configuration, DQE(0) increases between 2%–3% (absolute), while the corresponding improvement for the LKH-5 pixelated configuration was 7%. The performance of the weighting method was quantitatively evaluated with respect to spatial resolution, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of simulated planar images of phantoms at 2.5 and 6 MV. The line pair phantom acquisition exhibited a twofold increase in CNR and SNR, however MTF was degraded at spatial frequencies greater than 0.2 lp mm−1. For the Las Vegas phantom, the weighting improved the CNR by around 30% depending on the contrast region while the SNR values are higher by a factor of 2.5. These results indicate that the imaging performance of MLI systems can be enhanced using the proposed frequency-dependent weighting scheme. The CNR and SNR of the weighted combined image are improved across all spatial scales independent of the detector combination or photon beam energy.

The Synthesis of Nanophosphors YPxV1–xO4 by Spray Pyrolysis and Microwave Methods

За счет редкоземельного допирования фосфаты и ванадаты являются ведущими материалами для синтеза люминофоров благодаря их термостойкости, низкой температуре спекания, химической стабильности. Особый интерес привлекают люминофоры в наноразмерном состоянии. Простой, быстрый и масштабируемый синтез нанолюминофоров высокой химической гомогенности является актуальной задачей. Целью работы являлся синтез порошков смешанных кристаллов ванадат-фосфата иттрия различного состава методами соосаждения под действием микроволнового излучения и спрей-пиролиза, а также сравнительный анализ характеристик полученных образцов.Методами соосаждения под действием микроволнового излучения и спрей-пиролиза в различных режимах синтезированы образцы YVхP1–хO4 разного состава. Данные рентгенофазового анализа в случае синтеза ванадат-фосфата иттрия YVхP1–хO4 методом спрей-пиролиза с последующим отжигом подтверждают образование однофазных нанопорошков. Методами просвечивающей электронной микроскопии и растровой электронной микроскопии выявлены морфологические характеристики образцов. В зависимости от режима отжига образцы представляют собой ограненные либо сферические частицы размером менее 100 нм. Состав образцов YVхP1–хO4, синтезированныхметодом соосаждения под действием микроволнового излучения, сильно зависит от рН раствора прекурсоров.Минимальное содержание примесных фаз достигается при рН, равном 9.Метод спрей-пиролиза позволяет синтезировать нанопорошки ванадат-фосфата иттрия YVхP1–хO4 высокой химической гомогенности с размером частиц менее 100 нм. При синтезе YVхP1–хO4 методом соосаждения под действием микроволнового излучения максимальной химической однородности порошков ванадат-фосфата иттрия удается достигнуть при рН = 9. Однако дисперсия частиц по размеру велика, лежит в интервале 2–60 мкм. ЛИТЕРАТУРА 1. Wu C., Wang Y., Jie W. Hydrothermal synthesisand luminescent properties of LnPO4:Tb (Ln = La, Gd)phosphors under VUV excitation. Journal of Alloys andCompounds. 2007;436: 383–386. DOI: https://doi.org/10.1016/j.jallcom.2006.07.0562. Huang J., Tang L., Chen N., Du G. Broadeningthe photoluminescence excitation spectral bandwidthof YVO4:Eu3+ nanoparticles via a novel core-shell andhybridization approach. Materials. 2019;12: 3830. DOI:https://doi.org/10.3390/ma122338303. Wu Y., Zhang Z., Suo H., Zhao X., Guo C. 808 nmlight triggered up-conversion optical nano-thermometerYPO4:Nd3+/Yb3+/Er3+ based on FIR technology.Journal of Luminescence. 2019;214: 116478. DOI:https://doi.org/10.1016/j.jlumin.2019.1165784. Xiu Z., Wu Y., Hao X., Li X., Zhang L. Uniformand well-dispersed Y2O3:Eu/YVO4:Eu composite microsphereswith high photoluminescence prepared bychemical corrosion approach. Colloids Surf. A.2012;401(5): 68–73. DOI: https://doi.org/10.1016/j.colsurfa.2012.03.0215. Vats B. G., Gupta S. K., Keskar M., Phatak R.,Mukherjee S., Kannan S. The effect of vanadium substitutionon photoluminescent properties of KSrLa(-PO4)x(VO4)2x:Eu3+ phosphors, a new variant of phosphovanadates.New Journal of Chemistry. 2016;40(2):1799–1806. DOI: https://doi.org/10.1039/c5nj02951a6. Riwotzki K., Haase M. Colloidal YVO4:Eu andYP0.95V0.05O4:Eu nanoparticles: luminescence and energytransfer processes. The Journal of Physical ChemistryB. 2001;105(51): 12709–12713. DOI: https://doi.org/10.1021/jp01137357. Wu C.-C., Chen K.-B., Lee C.-S., Chen T.-M.,Cheng B.-M. Synthesis and VUV photoluminescencecharacterization of (Y,Gd)(V,P)O4:Eu3+ as a potentialred-emitting PDP phosphor. Chem. Mater. 2007;19(13):3278–3285. DOI: https://doi.org/10.1021/cm061042a8. Shimomura Y., Kurushima T., Olivia R., Kijima N.Synthesis of Y(P,V)O4:Eu3+ red phosphor by spray pyrolysiswithout postheating. The Japan Society of Applied.2005;44(3): 1356–1360. DOI: https://doi.org/10.1143/JJAP.44.13569. Lai H, Chen B., Xu W., Xie Y., Wang X., Di W. Fineparticles (Y,Gd)PxV1−xO4:Eu3+ phosphor for PDP preparedby coprecipitation reaction. Materials Letters.2006; 60 (11): 1341-1343. DOI: https://doi.org/10.1016/j.matlet.2005.11.05110. Singh V., Takami S., Aoki N., Hojo D., Arita T.,Adschiri T. Hydrothermal synthesis of luminescentGdVO4:Eu nanoparticles with dispersibility in organicsolvents. Journal of Nanoparticle Research. 2014;16(5):2378. DOI: https://doi.org/10.1007/s11051-014-2378-211. Song W.-S., Kim Y.-S., Yang H. Hydrothermalsynthesis of self-emitting Y(V,P)O4 nanophosphors forfabrication of transparent blue-emitting display device.Journal of Luminescence. 2012;132(5): 1278–1284.DOI: https://doi.org/10.1016/j.jlumin.2012.01.01512. Yu M., Lin J., Fu J., Han Y. Sol–gel fabrication,patterning and photoluminescent properties ofLaPO4:Ce3+, Tb3+ nanocrystalline thin films. ChemicalPhysics Letters. 2003;5(1-2): 178–183. DOI: https://doi.org/10.1016/S0009-2614(03)00239-213. Raoufi D., Raoufi T. The effect of heat treatmenton the physical properties of sol–gel derived ZnO thinfilms. Applied Surface Science. 2009;255(11): 5812–5817. DOI: https://doi.org/10.1016/j.ap-susc.2009.01.01014. Shao J., Yan J., Li X., Li S., Hu T. Novel fluorescentlabel based on YVO4:Bi3+, Eu3+ for latent fingerprintdetection. Dyes and Pigments. 2019;160: 555–562.DOI: https://doi.org/10.1016/j.dyepig.2018.08.03315. Dolinskaya Yu. A., Kolesnikov I. E., KurochkinA. V., Man’shina A. A., Mikhailov M. D., SemenchaA. V. Sol-Gel synthesis and luminescent propertiesof YVO4: Eu nanoparticles. Glass Physics and Chemistry.2013;39(3): 308–310. DOI: https://doi.org/10.1134/s108765961303006116. Томина Е. В., Сладкопевцев Б. В., Митто-ва В. О., Кнурова М. В., Латышев А. Н., Миттова И. Я.Микроволновый синтез и люминесцентные свой-ства YVO4:Eu3+. Неорганические материалы.2016;52(5): 495–498. DOI: https://doi.org/10.7868/S0002337X1605017117. Томина Е. В., Миттова И. Я., Бурцева Н. А.,Сладкопевцев Б. В. Способ синтеза люминофора наоснове ортованадата иттрия: патент на изобрете-ние № 2548089. Патентообладатель ФГБОУ ВПО «Воронежский государственный университет».№ 2013133382/05; заявл. 12.11.2013; опубл.20.05.2015.18. Томина Е. В., Куркин Н. А., Мальцев С. А.Микроволновый синтез ортоферрита иттрия идопирование его никелем. Конденсированныесреды и межфазные границы. 2019;21(20): 306–312.DOI: https://doi.org/10.17308/kcmf.2019.21/76819. Huang J., Gao R., Lu Z., Qian D., Li W., Huang B.,He X. Sol–gel preparation and photoluminescenceenhancement of Li+ and Eu3+ co-doped YPO4 nanophosphors.Optical Materials. 2010;32(9): 857–861.DOI: https://doi.org/10.1016/j.optmat.2009.12.01120. Brandon D., Kaplan W. D. MicrostructuralCharacterization of Materials. John Wiley & Sons Ltd;1999. 409 p. DOI: https://doi.org/10.1002/9780470727133

Clinical translation of a new flat-panel detector for beam’s-eye-view imaging

Electronic portal imaging devices (EPIDs) lend themselves to beams-eye view clinical applications, such as tumor tracking, but are limited by low contrast and detective quantum efficiency (DQE). We characterize a novel EPID prototype consisting of multiple layers and investigate its suitability for use under clinical conditions. A prototype multi-layer imager (MLI) was constructed utilizing four conventional EPID layers, each consisting of a copper plate, a Gd2O2S:Tb phosphor scintillator, and an amorphous silicon flat panel array detector. We measured the detector’s response to a 6 MV photon beam with regards to modulation transfer function, noise power spectrum, DQE, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and the linearity of the detector’s response to dose. Additionally, we compared MLI performance to the single top layer of the MLI and the standard Varian AS-1200 detector. Pre-clinical imaging was done on an anthropomorphic phantom, and the detector’s CNR, SNR and spatial resolution were assessed in a clinical environment. Images obtained from spine and liver patient treatment deliveries were analyzed to verify CNR and SNR improvements. The MLI has a DQE(0) of 9.7%, about 5.7 times the reference AS-1200 detector. Improved noise performance largely drives the increase. CNR and SNR of clinical images improved three-fold compared to reference. A novel MLI was characterized and prepared for clinical translation. The MLI substantially improved DQE and CNR performance while maintaining the same resolution. Pre-clinical tests on an anthropomorphic phantom demonstrated improved performance as predicted theoretically. Preliminary patient data were analyzed, confirming improved CNR and SNR. Clinical applications are anticipated to include more accurate soft tissue tracking.

Spectral study on energy transfer of the LiMgPO4 phosphor doped with Tm3+ and Tb3+

LiMgPO4(LMP):Tm, LMP:Tb and LMP:Tm, Tb phosphors were synthesized via a high-temperature solid-phase method, and the crystal structures of the samples were studied by X-ray diffraction (XRD). Thermoluminescence (TL) and optically stimulated luminescence (OSL) curves and TL three-dimensional (3D) spectra of the LMP phosphors doped with Tm3+ and Tb3+ were measured. The photoluminescence (PL) of the samples was also measured to study the effects of Tb3+ and Tm3+ ions on the luminescence of the material, its concentration on the luminescence properties, and the energy transfer between the two kinds of ions. The experimental results showed that in the co-doped system of LMP:Tm,Tb, the rare earth ions, Tm3+ and Tb3+, become the discrete luminescent centre, Tm3+ ions act as activators, and Tb3+ ions act as sensitizers. Upon analysing the PL lifetime of Tm3+ and Tb3+, energy transfer from Tb3+ to Tm3+ was found. According to the TL 3D spectra of LMP:Tm,Tb, the TL luminescence of Tb3+ below 200 °C was suppressed, and the TL luminescence of Tm3+ at approximately 300 °C was enhanced. This showed that the energy of the low-temperature glow peaks transferred to the 300 °C peak, meaning that the formation of shallow traps was inhibited, which is beneficial for the stability of the sample signal and improves the sensitivity of the sample to the high-temperature peak. Moreover, the TL and OSL intensities of the LMP:Tm, Tb phosphor were comparable to that of Al2O3:C; thus, it can be applied for a low-dose measurement.

Acid-Base and Luminescent Properties of Gd<sub>2</sub>O<sub>2</sub>S: Tb Luminescent Phosphors Synthesized in a Reducing Atmosphere

Gd2O2S:Tb phosphors with different terbium content are prepared in a reducing atmosphere at various synthesis conditions. The effect of an activator and Na4P2O7 flux concentrations upon photo-and X-ray induced luminescence of the synthesized samples as well as on their acid-base properties and morphology is studied. The addition of Na4P2O7 flux into the charge mixture leads to a significant increase of the phosphor particle size. A positive correlation is found between the particle size and pH value of the phosphor aqueous slurry. The photoluminescence intensity is found to mostly depend on the activator concentration, while X-ray luminescence intensity primarily depends on the particle size and crystal structure perfectness of the phosphor matrix. Charge mixture compositions and synthesis conditions providing Gd2O2S:Tb phosphors with the highest photo-and X-ray luminescence intensity are determined. A Gd2O2S:Tb phosphor with X-ray luminescence intensity exceeding the values for the commercial phosphor KEP-45 of a similar composition is developed. The obtained phosphors can be used for the manufacture of intensifying screens applied in industrial X-ray flaw detection.