Dy Phosphor Research Articles

Energy transfer mechanism and new ratiometric thermometry strategy by the blue and yellow emissions of Dy

In this paper, we report the energy transfer mechanism between Dy3+ ions as well as a new optical ratiometric thermometry strategy in Dy3+ doped CaWO4 (CaWO4:Dy) phosphors. The optimal Dy3+ doping concentration was determined and the electric dipole-dipole interaction among Dy3+ was investigated based on the analysis of the concentration-dependence luminescent properties in CaWO4:Dy phosphors. The photoluminescence (PL) of two blue and two yellow emissions produced by Dy3+ transitions from the thermally coupled energy levels (TCLs) of 4I15/2/4F9/2 to the 6H15/2 ground level and 4I13/2 metastable level, respectively, exhibited opposite PL behavior with increasing temperature. The luminescence intensity ratio (LIR) between blue and yellow emissions (B/Y) was discovered to have a quantitative relationship with temperature based on the classic thermalized population distribution of TCLs. In comparison to traditional thermometry based on the LIR of two blue emissions, the proposed new ratiometric thermometry based on the LIR of B/Y demonstrated good optical thermometry behavior with extended temperature detection range to cryogenic region, excellent absolute sensitivity, good repeatability, and high accuracy, which can also be applied to other Dy3+ doped materials such as Y3Al5O12 and NaYF4 phosphors using either down- or up-conversion PL of blue and yellow emissions.

Thermoluminescence characterization and kinetic parameters of Dy3+ activated Ca3Y2B4O12

In this study, thermoluminescence (TL) characteristics of Ca3Y2B4O12:xDy (0 ≤ x ≤ 0.07) phosphor samples were studied. The samples were exposed to beta irradiation in the dose range from 0.1 Gy to 100 Gy to investigate TL dose response. The concentration of Dy3+ in Ca3Y2B4O12 phosphor was optimized and found to be 1 mass % in terms of TL signal quality. The TL glow curve appears to be consisted of three peaks which were discernible at 72 °C, 280 °C and 376 °C. The trapping parameters (E, b, and s) were calculated using initial rise (IR), and variable heating rate (VHR) techniques. The trapping parameters, order of kinetics, frequency factor, and figure of merit have been all determined by means of the Glow Curve Deconvolution (GCD) method (tgcd:An R package). Ca3Y2B4O12:Dy phosphor displays efficient thermoluminescence properties.

A preliminary study of the radioluminescence and optically stimulated luminescence of CaF2:Ce,Dy phosphor

The aim of this work was to study the radioluminescence (RL) and optically stimulated luminescence (OSL) properties of CaF2:Ce,Dy. For this purpose, samples of CaF2:0.4 mol% Ce,0.4 mol% Dy in pellet form were used. Experimental results have shown that the inclusion of Ce and Dy in this phosphor provides a good OSL sensitivity in a wide dose range from 0.022 up to 126 Gy. Besides, a minimum detectable dose of 0.01 Gy and an OSL fading of approximately 30% after 20 h of storage in darkness were found. Finally, the RL and OSL signals of CaF2:Ce,Dy are compared with those of the commercial TLD-200 (CaF2:Dy) dosimeter.

Comparative study on SrAl2O4 formation using different approaches

A comparative study on SrAl2O4 synthesis via solid-state reaction and combustion synthesis was performed, based on thermodynamic calculations and resulted sample characteristics. We proposed a first-time approach of the combustion synthesis using metal perchlorates and a fuel mixture of urea and glycine. The calculated adiabatic temperature of the combustion reaction was 2807 °C and the standard enthalpy of reaction was - 6093 kJ/mol SrAl2O4. The recorded temperature during the highly exothermic combustion reaction was 1757 °C. The solid-state reaction was endothermic, with a standard enthalpy of reaction of 330 kJ/mol SrAl2O4. The precursor mixtures and obtained samples were characterized and compared in terms of temperature behavior, phase composition, crystallite size, specific surface area and morphology. The results prove the superiority of the proposed approach in terms of thermal efficiency and open a new perspective upon the use of strontium and aluminum perchlorates in the combustion synthesis of highly crystalline SrAl2O4-based materials, such as SrAl2O4: Eu, Dy phosphors.

Structure and luminescent properties of Dy3+ activated NaLa9(SiO4)6O2 yellow-emitting phosphors for application in white LEDs

A series of Dy3+-doped sodium lanthanum orthosilicate oxyapatites, NaLa9−xDyx(SiO4)6O2 (NLSO:xDy, x = 0–0.3), were synthesized by the solid-state reaction method at 1100 °C, with the aim of developing yellow emitting phosphors for applications in w-LEDs. Their crystal structure, morphology and particle size distribution, electronic structure, Raman spectra, concentration- and temperature-dependent luminescent properties were investigated for the first time. The crystal structure was refined by the Rietveld method. Undoped NLSO is hexagonal (space group P63/m – C26h) with lattice constants a = b = 9.6917(3) Å and c = 7.1836(4) Å. It is shown that Dy3+ ions substitute for the La3+ ones in two types of sites with C3 and Cs point symmetries. The first-principle calculations for undoped NLSO revealed an indirect bandgap of 5.06 eV. The NLSO:0.2Dy phosphor exhibited intense yellow emission with CIE 1931 chromaticity coordinates of (0.469, 0.495) and a correlated color temperature of 3150 K owing to the hypersensitive electric-dipole transition 4F9/2→6H13/2 (571 nm) dominating in the luminescence spectrum. Excellent thermal stability was found for this apatite phosphor (the activation energy is 0.23 ± 0.02 eV).

Green synthesis, structure feature and energy transfer of yellow‐emitting (Y,Gd)2O2SO4:Dy phosphors

AbstractA green chemical precipitation route was used to yield a hydrated basic sulfate precursor upon calcination at 1000°C into a series of (Y,Gd)2O2SO4:Dy particles. The phosphors exhibited characteristic Dy3+ emissions from 4F9/2→6HJ (J = 15/2, 13/2, 11/2) transitions under ultraviolet light excitation; the quenching concentration of Dy3+ was determined to be 2.5 at.%. Substitution of Gd3+ for Y3+ led to an additional strong sharp band at ~277 nm (8S7/2→6IJ transition of Gd3+) in the photoluminescence excitation spectra, upon which the (Gd0.975Dy0.025)2O2SO4 phosphor achieved a ~2.8‐fold higher photoluminescence intensity via an effective energy transfer from Gd3+ to Dy3+ compared with the 354 nm excitation of Dy3+. Both the photoluminescence and photoluminescence excitation intensities of (Y,Gd)2O2SO4:Dy phosphors increased with rising Gd3+ concentration and calcination temperature in the range 750–1000°C. A higher Gd3+ concentration slightly prolonged the effective fluorescence lifetime.

Evaluation of SrAl2 O4 :Eu, Dy phosphor for potential applications in thermoluminescent dosimetry.

PurposeTo evaluate the use of commercial‐grade strontium aluminate phosphorescent powder as a thermoluminescent (TL) dosimeter for clinical radiotherapy beams.Materials and MethodCommercially available Eu2+, Dy3+ co‐doped strontium aluminate powder (SrAl2O4:Eu, Dy) was annealed and then irradiated using 20 × 20 cm2 field size, with 6‐MV (PDD10 = 70.7) and 18‐MV (PDD10 = 79.4) photon beams and and 9‐MeV (R50 = 3.6), 15 MeV (R50 = 5.9) and 18‐MeV (R50 = 7.2) electron beams. To calibrate the relationship between the TL readings and the irradiated doses, TL glow curves were acquired for doses up to 600 cGy at all beam energies. For the percentage depth dose (PDD) measurement, the SrAl2O4:Eu, Dy powder was sandwiched by solid water phantoms, with varying thickness of solid water placed above to determine the depth. PDDs were measured at four representative depths and compared against the commissioning depth dose data for each beam energy.ResultsLinear dose response models of doses up to 200 cGy were created for all beam energies. Superlinearity was observed with doses greater than 200 cGy. The PDD measurement acquired experimentally agrees well with the commissioning data of the medical linear accelerator. Trapping parameters such as order of kinetics, activation energy and frequency factor have been obtained via TL glow curve analysis.ConclusionThe linear dose response demonstrates that SrAl2O4:Eu, Dy is a potential TLD dosimeter for both electron beams and photon beams at different beam energies. The PDD measurements further support its potential use in quality assurance and radiation dosimetry.

Study of TL characteristics of CaSO4: Dy phosphor with fly ash for thermoluminescence dosimeter application

In recent past fly ash is only being treated as waste and a source of air and water pollution but is in fact an eco - friendly and economically beneficial resource material for various applications and has also proven its worth over a period of time. The utilization of fly ash in several novel researches will also paves the path for systematic disposal of this waste material. The present paper involves the study of Thermoluminescence (TL) of different compositions of fly ash collected from National Thermal Power Corporation, Korba, Chhattisgarh, INDIA with (CaSO4:Dy) Phosphor. Thermo luminescence Dosimeters are regarded as the badge which absorbs the radiation when persons having TLD badges are exposed to radiation. We have to investigate and compare the glow curve behavior of pure phosphor and 10 %, 20 % and 30 % fly ash doped phosphor when it is exposed to gamma irradiation Cs137.

Effect of Mn codopant on thermoluminescence properties of γ-rays irradiated Na3Y(PO4)2:Dy phosphors for dosimetry applications

Effect of Mn codopant on thermoluminescence properties of γ-rays irradiated Na3Y(PO4)2:Dy phosphors for dosimetry applications

Photoluminescence characterization of some Vanadate based phosphors

Highly efficient new vanadate phosphor A2NaMg2V3O12 (A = Ba & Sr) doped with rare earth element Dysprosium (Dy) was synthesized at high temperature via solid-state method successfully and the formed compound was confirmed by X-ray diffraction method. Photoluminescence measurements revealed that Sr2NaMg2V3O12 phosphor doped with Dy is excited by near ultraviolet light ranging from 300 nm to 380 nm efficiently in order to realize the emission in visible spectrum (in the range 400 nm −570 nm. Ba2NaMg2V3O12: Dy phosphor also showed emission at 569 nm on excitation at 325 nm. Hence this prepared phosphor can find application as a green emitting phosphor in solid state lighting area.

Facile synthesis and thermoluminescence properties of nano bio-ceramic \u03b2-Ca2P2O7:Dy phosphor irradiated with 75\xa0meV C6+ ion beam

Dy3+ doped β-Ca2P2O7 phosphor has been synthesized using wet chemical method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis confirmed the formation of β-Ca2P2O7:Dy nano-phosphors. However, photoluminescence (PL) study was carried out to confirm the presence of dopant ion in the host matrix of β-Ca2P2O7:Dy material. Thermoluminescence (TL) glow curves of β-Ca2P2O7 were recorded for different concentrations of Dy3+ after exposure to various fluences of C6+ ion beam (75 meV). TL sensitivity of β-Ca2P2O7:Dy3+ (0.1 mol%) phosphor was 3.79 times more than commercially available CaSO4:Dy3+. TRIM code based on the Monte Carlo simulation was used to calculate the absorbed doses, ion range and main energy loss. Glow curve de-convolution (GCD) method was used to determine the number of TL peaks and their trapping parameters. The wide linear response of β-Ca2P2O7 nanoparticles along with high stability of TL glow curve makes this nanomaterial a good candidate for C6+ ion beam dosimetry.

Thermoluminescence in MgB4O7:Pr,Dy dosimetry powder synthesized by solution combustion synthesis method

This study aimed to investigate the dosimetric properties of magnesium tetraborate (MgB4O7) doped with praseodymium (Pr3+) and dysprosium (Dy3+) using the thermoluminescence (TL) technique. In this study, the dopant concentrations of Pr0.01–2% wt and Dy0.01–20% wt were induced into MgB4O7 with Solution Combustion Synthesis (SCS) method. Their effect was enhanced sensitivity of TL when used with the optimal dopant concentrations Pr0.5% wt and Dy5% wt incorporated in the lattice. The structural characterizations of MgB4O7:Pr0.5%wt,Dy5% wt phosphor was studied using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) analysis techniques. X-ray Luminescence (XL) spectra of several of these phosphors with various dopants as used here, were also determined. The TL glow curve of the MgB4O7:Pr0.5% wt, Dy 5% wt phosphor consists of four TL peaks at ~ 85, ~180, ~265, ~320 °C when recorded with a heating rate of 2 °C/s without preheating. Some dosimetric properties of the MgB4O7:Pr,Dy phosphor, such as dose-response, reusability and fading in dark were studied under 90Sr/90Y beta-ray radiation. The TL output was found as linear with dose from 0.1 to 100 Gy. The good reusability, by 2% standard deviation, was up to 20 experimental cycles. After 24 h, the maximum heights of TL glow peaks at 180 and 320 °C were about 7 and 4% less than that of the readouts at half an hour later the irradiation. The kinetic parameters using various heating rate (VHR), Tm-Tstop assisted extended initial rise method (IRM) and computerized glow curve deconvolution (CGCD) techniques were obtained and compared. Experimental results suggest that Pr3+ and Dy3+ doped MgB4O7:Pr0.5% wt,Dy5% wt shows suitable dosimetric properties for TL dosimetry.

Photocatalytic Properties of g-C3N4–Supported on the SrAl2O4:Eu,Dy/SiO2

Graphitic carbon nitride (g-C3N4) was supported on SrAl2O4:Eu,Dy-SiO2 by a colloidal-sol coating method to improve its light absorption property. Transmission electron microscopy (TEM) revealed that the nanoparticles of g-C3N4 were coated on sub-micron phosphor particles and nanoscale surface roughness was imparted by the SiO2-binder. Photoluminescence (PL) spectrum of the g-C3N4 supported on SrAl2O4:Eu,Dy exhibited a broadband emission from 400 to 650 nm. Increasing silica-binder in the g-C3N4/SrAl2O4:Eu,Dy composites suppressed the PL emission peak at 525 nm for SrAl2O4:Eu,Dy. Photocatalytic degradation activity was evaluated with 5 ppm methylene blue (MB) solutions under germicidal ultraviolet (UV) and visible (Vis) solar light illuminations. The UV/Vis photocatalytic efficiency was improved by supporting g-C3N4 on the SrAl2O4:Eu,Dy phosphor and with the addition of SiO2 as a binder. In addition, low silica addition effectively improved the adhesiveness of the g-C3N4 coating on the SrAl2O4:Eu,Dy surface. Recyclability tests of photocatalysis for the SrAl2O4:Eu,Dy-0.01M SiO2/50wt% g-C3N4 composites exhibited a remarkable stability by maintaining the degradation efficiencies above 90% in four cycles. Therefore, the composite of g-C3N4-supported SrAl2O4:Eu,Dy-SiO2 is a prospective photocatalyst activating under UV/Vis light irradiation for the elimination of environmental pollutants.

Cathodoluminescence properties of La2MoO6:Ln3+ (Ln: Eu, Dy, and Sm) phosphors

La2MoO6 orange-red phosphors with high efficiency incorporated with Eu, Dy and Sm have been synthesized through a gel combustion method. The influences of rare earth doping in synthesized samples were analysed by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and cathodoluminescence. Rare earth doped La2MoO6 samples show strong emission bands in the range of 400–750 nm and optimal doping concentration for all samples was 2 mol%. La2MoO6 host doped Eu ion showed intense and predominant emission peaks in 450–750 nm range. The electrical multipolar interaction contributed to the non-radiative energy transfer between Eu3+ ions in La2MoO6 host matrix. Sm doped La2MoO6 host exhibited orange-red CL emission peaks at 564, 608, 652 and 708 nm La2MoO6:Dy3+ phosphor displayed emissions at 484, 574 and 670 nm, respectively. The observed intense and sharp emission peaks indicate that La2MoO6 is promising host for lanthanides doped phosphor materials in the applications of optoelectronic.

Multicolor emission leading by energy transfer between Dy3+ and Eu3+ in wolframite InNbTiO6

Exploring new color-tunable phosphors is of significance for light-emitting applications. In this work, multicolor-emitting InNbTiO6:Dy3+,Eu3+ phosphors were formulated and synthesized using the classic solid-state reaction technique. Phase identification indicates the pure wolframite crystal structure of as-prepared samples. According to the Rietveld refinement, dopants have been confirmed to occupy the In3+ site in the InNbTiO6 matrix. The phosphors exhibit strong absorption around 385 and 394 nm, due to the dominated transitions of 4F9/2->6H13/2 in Dy3+ and 5D0->7F2 in Eu3+, respectively, well matching the emissions from the commercial UV LED chips. In single doped phosphors, activators Dy3+ and Eu3+ under the UV light excitation respectively present their unique emission lines. As for the codoped phosphors, the co-activation and sensitization between Dy3+ and Eu3+ have been elucidated under a 394 nm excitation. The addition of Eu3+ into InNbTiO6:0.06Dy phosphor leads to the emission tuning from grass-green to orange-red crossing the warm-white region. The energy transfer can be proved through analyzing the PLE and PL profiles of the co-activated phosphors and evaluating the decay process for Dy3+ ions. According to the Dexter's theory and Reisfield's approximation, the mechanism of coupling effect has been identified to be the electric d-d (dipole-dipole) interaction. When the sum of dopants concentration equals to 0.09, the energy transfer efficiency reaches the maximum value 40.5. Moreover, the thermal stability of a representative InNbTiO6:0.06Dy3+,0.015Eu3+ phosphor have been investigated, which presented and a emission intensity maintenance of 42% at 423 K relative to room temperature 298 K. Besides, the quantum yields of InNbTiO6:0.06Dy3+, 0.04Eu3+ within the luminescence range 603–620 nm are measured to be 33.4% under the ultraviolet radiation of 394 nm. These results demonstrate that these new type phosphors have promising applications in UV LED based white light-emitting devices.

SrAl2O4:Eu,Dy mechanoluminescent flexible film for impact sensors

The present work is devoted to make a mechanoluminescent film for making an impact sensor that is flexible, durable and non-destructive. For this, a flexible film of SrAl2O4:Eu,Dy phosphor is prepared by mixing SrAl2O4: Eu,Dy with polydimethylsiloxane (PDMS). The XRD patterns indicate the formation of a monoclinic phase of SrAl2O4: Eu,Dy phosphor. The SEM images reveal the surface morphology of the reported samples (powder and film). In order to measure the mechanoluminescence (ML) intensity, the flexible film is excited impulsively with a steel ball. Snapshots of ML patterns taken with cathode ray oscilloscope are presented to visualize the activity exactly. Variations in peak ML intensity and total ML intensity with time are discussed. The photoluminescence (PL) spectra are found to peak at 520 nm when excited with 365 nm wavelength. The broad green emission obtained from flexible film is attributed to 4f65 d1→4f7 transitions. The time corresponding to peak ML intensity (tm) does not change much with increasing impact velocity of the steel ball. The ML behaviour under cyclic loading is also recorded and analyzed. When SrAl2O4:Eu,Dy flexible ML film is rubbed with smooth glass rod, it produces the ML pulses of different intensities. These characteristics are useful for the development of the pressure and impact sensors.

Synthesis and competitive luminescence quenching mechanism of Ca3Al2O6:Ln3+ (Ln: Dy and Sm) phosphors

Sm3+ and Dy3+ activated Ca3Al2O6 phosphors were produced through a gel combustion method using Urea + β-Alanine, Urea, and Urea + Glycine as fuels. The crystal structure and the phase purity of the obtained materials were characterized by X-ray powder diffraction (XRD). Ca3Al2O6:Sm3+ phosphor shows characteristic emission lines (565 nm, 602 nm, 649 nm, and 714 nm) in the orange red region assigned to 4G5/2→6HJ (J = 5/2, 7/2, 9/2, 11/2) transitions of Sm3+. The strongest peak is located at 602 nm. Emission spectra of Ca3Al2O6:Dy3+ show that there are two dominant peaks centered at 480 nm and 573 nm emitting blue and yellow light. Optimum doping concentrations of Sm(NO3)3 and Dy(NO3)3 are 0.01 % and 0.03 %, respectively. The concentration quenching mechanism is verified to be a dipole-dipole interaction as the type of energy transfer among Sm3+-Sm3+ and Dy3+-Dy3+ ions. The critical distance is also calculated to be 24.19 Å and 16.77 Å, respectively.

Effects of doping ions on the luminescence performance of terbium doped gadolinium polysulfide phosphor

Gd2O2S: Tb (GOS) phosphor screen has been widely used in digital X-ray imaging, and so far, numerous studies have been focused on the doping ions to improve the luminescence performance of the GOS phosphors. GOS: Tb, Dy phosphors were synthesized by the solid-state reaction process, and their phase composition, particle size, morphology and luminescence properties were characterized. The results showed that co-doping Dy3+ can promote the luminescence and the optimal doping concentration of Dy3+ ions were about 0.2%, however concentration quenching will occur when the doping concentration exceeded 0.5%. Ta5+ ion was also studied in the GOS: Tb and GOS: Tb; Dy phosphors prepared by the same method. The results showed that when the Ta5+co-doping concentration was 100ppm, the strongest emitted light intensity would be obtained for both phosphors. The photoluminescence spectra revealed a different influencing mechanism of Ta5+ ion comparing to Dy3+, which is by a strong energy transfer between Dy3+ and Tb3+.

Synthesis, crystal structure, optical and adsorption properties of BaAl2O4: Eu2+, Eu2+/ L3+ (L = Dy, Er, Sm, Gd, Nd, and Pr) phosphors

In this work, the BaAl2O4: Eu2+, Eu2+/L3+ (L= Dy, Er, Sm, Gd, Nd, and Pr) phosphors were synthesized via a facile solid-state reaction method using LiCl as a flux material at 1100 °C. The structural properties, microstructure, adsorption and photoluminescence characteristics of products were evaluated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Uv–vis adsorption and photoluminescence (PL) analyses. The observation of XRD patterns showed that even 10% LiCl is not able to produce any impurity phase in BaAl2O4: Eu2+ crystal structure, although the microstructure morphology is considerably affected. The particle size of BaAl2O4: Eu2+ phosphors was about 220 nm while the use of LiCl flux resulted in a remarkable decrease of this parameter to about 120 nm. Furthermore, the PL patterns disclosed that Eu2+ ions have occupied one type of Ba2+ sites while larger quantities of lanthanides (L3+) occupied the second type of Ba2+ sites. The strongest photoluminescence emission intensity at the wavelength of 495 nm was achieved when 5 wt% LiCl was added to BaAl2O4: Eu2+. Also, the absorption analysis revealed that the addition of flux enriches the adsorption of Congo red (CR) dye on the phosphor powders. The use of 5 wt% flux material led to noticeable improvement of CR adsorption capacity from 38.53 to 48.3 mg g−1.

Particle size dependent TL response of CaF2:Dy phosphor for gamma dosimetry

CaF2:Dy phosphor was prepared by ball milling method over particle size ranging from 140 nm to 35 nm, and their thermoluminescence properties were studied by irradiation with 60Co gamma rays. The XRD revealed that the crystallite size was of ∼45 nm for pristine, 19.1 nm for 10 h and 9.99 nm for 50 h ball-milled phosphor samples and confirmed by FESEM. The UV–visible spectra indicate that the absorption and scattering of radiation increased with a decrease in the particle size along with the blue shift in the absorption peak. CaF2:Dy particles of different sizes were irradiated with gamma dose from 1 Gy to 20 kGy and respective thermoluminescence response was studied. It was observed that the ∼65 nm particle size phosphor showed a linear response with gamma dose range from 1 Gy to 12 kGy. These results reveal that the CaF2:Dy phosphor can be used for high gamma radiation measurement and food irradiation dosimetry.