Long afterglow yellow luminescence from Pr3+ doped SrSc2O4

A yellow emitting long afterglow luminescence material SrSc₂O₄:Pr³⁺ was successfully prepared by solid state reaction method. SrSc₂O₄:Pr³⁺ phosphor shows a long afterglow luminescence peak at about 495, 545, 621, 630 and 657 nm, respectively, corresponding to the f–f transitions of Pr³⁺. The afterglow chromaticity coordinates of SrSc₂O₄:1 at%Pr³⁺ were calculated to be (0.35, 0.41), indicating that the afterglow emission is close to the light of yellow region. And, the afterglow luminescence of the optimal sample doped by 1 at%Pr³⁺ can persist for over 3 h. The thermoluminescence results suggest that there are three types of traps with depth of 0.61, 0.69 and 0.78 eV exiting for all the samples, which are produced by the addition of Pr³⁺ ions. The trap density of SrSc₂O₄:1 at%Pr³⁺ is the maximum when the incorporation of Pr³⁺ ions reaches 1 at%, which thus results in the longest afterglow luminescence. All the results indicate that SrSc₂O₄:Pr³⁺ can be a potential candidate of novel long afterglow phosphors.     

Energy transfer and luminescent properties of Tb3+ and Tb3+, Yb3+ doped CNGG phosphors

In this work,calcium niobium gallium garnet(Ca₃ Nb_1.6875Ga_3.1875O₁₂-CNGG) ceramic samples singledoped with Tb³⁺ and co-doped with Tb³⁺ and Yb³⁺ ions were sintered by the solid-state reaction method.The structural characterization of the samples was carried out by X-ray diffraction measurements.The optimal concentration of Tb³⁺ ions corresponding to the maximum luminescence in the green spectral range in CNGG:...     

A comparison research on replacements of Ba2+ by Lu3+ and Ba2+-Si4+ by Lu3+-Al3+ in BaSi2O2N2:Eu phosphors

As a cyan-emitting oxonitridosilicate phosphor,BaSi₂O₂N₂:Eu²⁺can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba²⁺by Lu³⁺and Ba²⁺-Si⁴⁺by Lu³⁺-Al³⁺can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu³⁺doping,the internal quantum efficiencyηIQE Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺is 24.08%higher than that of Ba_0.97Si₂O₂N₂:0.03 Eu²⁺.After Al³⁺co-doping,theηIQE is further increased by 10.31%compared to Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺.When the temperature rises to 473 K,the luminescence intensity of Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba_0.97Si₂O₂N₂:0.03 Eu²⁺,while the luminescence intensity of Ba_0.925Si_1.97O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺,0.03 Al³⁺keeps 73.87%of the initial value,which increases by18.52%compared to Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺.The mechanisms for luminescence and thermal stability improvement are proposed.The Ba_0.925Si_1.97O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺,0.03 Al³⁺cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu²⁺red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi₂O₂N₂:Eu²⁺,Lu³⁺,Al³⁺phosphor has great application prospect in the field of full-spectrum lighting.     

Luminescent performance of rare earths doped CaBi2Ta2O9 phosphor

A series of red-emitting phosphors of CaBi₂Ta₂O₉:Pr³⁺ and CaBi₂Ta₂O₉:Eu³⁺ were synthesized by the solid-state reaction method. The crystal structure and photoluminescence properties were investigated by X-ray diffraction (XRD) and photoluminescence spectra. The emission spectra showed that the red emission peaks were located at 622 nm for Pr³⁺ and 615 nm for Eu³⁺, respectively. The optimal doping concentrations for Ca_1?xBi₂Ta₂O₉:xPr³⁺ and Ca_1?yBi₂Ta₂O₉:yEu³⁺ were x=0.02 and y=0.15, respectively. The effect of fluxes (H₃BO₃, NH₄F, CaCl₂ and CaF₂) and charge compensations (Li₂CO₃, Na₂CO₃ and K₂CO₃) on luminescent properties were investigated in detail. It was found that the relative emission intensity of Ca_0.98Bi₂Ta₂O₉:0.02Pr³⁺ with 10 mol.% H₃BO₃ flux was about 2.9 times higher than that of the sample without flux. The relative emission intensity of Ca_0.7Bi₂Ta₂O₉:0.15Eu³⁺, 0.15K⁺ was about the 2.1 times higher than that of Ca_0.85Bi₂Ta₂O₉:0.15Eu³⁺.     

Effects of Sr2+ on structure and luminescent properties of BaAl12O19:Eu phosphors

Ba_0.9-ySr_yAl₁₂O₁₉:Eu_0.1 phosphors were prepared by sol-gel technique, the crystalline structures of samples characterized by XRD, and the luminescence properties were investigated. The influence of crystallographic positions on the luminescent properties of Sr²⁺-doped BaAl₁₂O₁₉:Eu was investigated in detail. The results indicated that the crystal lattice of BaAl₁₂O₁₉:Eu was not influenced by the Sr²⁺ and doping Sr²⁺ in BaAl₁₂O₁₉:Eu enhanced the luminescent properties of the phosphors at the proper concentration of Sr²⁺. With the increasing of concentration of Sr²⁺ doped in BaAl₁₂O₁₉:Eu, the relative luminescent intensity of Ba_0.9-ySr_yAl₁₂O₁₉:Eu_0.1 strengthened and blue-shifted.     

Elevating photoluminescence properties of Y3MgAl3SiO12:Ce3+ transparent ceramics for high-power white lighting

Compared with Y₃Al₅O₁₂:Ce³⁺,Y₃MgAl₃SiO₁₂:Ce³⁺(YMASG:Ce³⁺) reveals great potential for highpower white lighting with red-shift spectrum.Herein,YMASG:Ce³⁺ transparent ceramics were explored to be synthesized in the air following hot isostatic pressure(HIP) treatment to obtain tunable and optimized optical properties.Then phase purity,microstructure,transmittance,and photoluminescence of YM...     

Synthesis of Long Afterglow Phosphors Doped B SrAl2O4:Eu2+, Dy3+ and Its Luminescent Properties

The long afterglow luminescent material SrAl₂O₄: Eu²⁺, Dy³⁺ was prepared by high temperature solid-state method. Effects of doped B on the luminescent properties of phosphors SrAl₂O₄: Eu²⁺, Dy³⁺ were investigated by means of excitation spectra, emission spectra and X-ray diffraction analysis. As the result, the addition of H₃BO₃ as flux promotes the growth of crystalline and reduces the synthesizing temperature, but the wavelength of emission peak of photoluminescent material did not change with the variation of H₃BO₃ content. The effect of Dy³⁺ concentration on the luminescent properties of material was investigated. It was found that the luminescence of phosphors prepared under the condition of the amount of H₃BO₃ 5% and the mole ratio of Eu/Dy = 1/7(Eu = 0.02 mole) had better luminescent property and longer afterglow time.     

Synthesis and enhanced photoluminescence properties of red emitting divalent ion (Ca2+) doped Eu:Y2O3 nanophosphors for optoelectronic applications

This work presents the synthesis of Y₂O₃:Eu³⁺,xCa²⁺ (x = 0 mol%, 1 mol%, 3 mol%, 5 mol%, 7 mol%, 9 mol%, 11 mol%) nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic, display, and lighting applications. The X-ray diffraction (XRD) patterns of the proposed nanophosphor reveal its structural properties and crystalline nature. The transmission electron microscope (TEM) results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca²⁺. Fourier transform infrared spectroscopy (FTIR) and Raman vibrations also confirm the presence of Y–O vibration and subsequently explain the crystalline nature, structural properties, and purity of the samples. All the synthesized nanophosphors samples emit intense red emission at 613 nm (⁵D₀→⁷F₂) under excitation with 235, 394 and 466 nm wavelengths of Eu³⁺ ions. The photoluminescence (PL) emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength, respectively. The emission intensity of Y₂O₃:Eu³⁺,xCa²⁺ (5 mol%) is increased 8-fold as compared to Eu:Y₂O₃. Doping with Ca²⁺ ions enhances the emission intensity of Eu:Y₂O₃ nanophosphors due to an increase in energy transfer in Ca²⁺→Eu³⁺ through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix. It is also observed that the optical band gap and the lifetime of the ⁵D₀ level of Eu³⁺ ions in Y₂O₃:Eu³⁺,xCa²⁺ nanophosphor sample gets changed with a doping concentration of Ca²⁺ ions. Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%, respectively. CIE, CCT, and color purity values (>98%) show an improved red-emitting nanophosphor in the warm region of light, which makes this material superior with a specific potential application for UV-based white LEDs with security ink, display devices, and various other optoelectronics devices.     

Fabrication and comprehensive structural and spectroscopic properties of Er:Y2O3 transparent ceramics

Transparent Er:Y₂O₃ ceramics with sub-micron grain size (<1 μm) were fabricated by using one-step vacuum sintering followed by hot isostatic pressing (HIPing) technique. The transmission of the undoped Y₂O₃ reaches 83%. The structural characteristics including the phonon energy were investigated through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) measurement. The overall spectroscopic properties of transmission, fluorescence emission up to 3000 nm, lifetime, up-conversion luminescence, and refractive index were systematically studied for both 0.25 at% and 7.0 at% Er:Y₂O₃ ceramics with different thicknesses. The comparison of the spectra of the fluorescence emission and up-conversion luminescence under both 976 and 808 nm laser excitation was performed. The multiple high-energy-state transitional processes after the excited state absorption (ESA) processes involved in the up-conversion are discriminated between the multi-phonon non-radiative transitions and the radiative transitions according to the measured maximum phonon vibrational energy. The calculation was performed based on the Judd–Ofelt theory.     

Glass forming regions and concentration-dependent luminescence properties of Tb~(3+)-activated tellurium-lutetium-tungsten glasses

The glass-forming regions of tellurium-gadolinium-tungsten ternary system prepared at 1000℃for 60 min were firstly determined.To improve density,the full replacement of lutetium for gadolinium to form Tb³⁺-activated tellurium-lutetium-tungsten glasses with the composition of 64 TeO₂-20 WO₃-(16-y)Lu₂O₃-yTb₂O₃were designed for scintillation application.The concentration-dependent optical properties of Tb³⁺-activated tellurium-lutetium-tungsten glasses were fully investigated by transmittance,excitation and emission spectra,together with the luminescence decay curves.The energy transfer mechanism was discussed according to Huang’s rule.The optimized 4 mol%Tb₂O₃activated tellurium-lutetium-tungsten glasses with the density of 6.49 g/cm³and the lifetime of 0.551 ms are developing to be suitable for the potential detection of slow events in the future work.     

Optical and luminescence characteristics of Eu3+-doped B2O3:SiO2:Y2O3:CaO glasses for visible red laser and scintillation material applications

Europium(Eu~(3+)) doped glasses of chemical compositions(55-x)B_2O_3:10 SiO_2:25 Y_2O_3:10CaO:xEu_2O_3,where x denotes mol% and ranges 0≤ x ≤ 2.5, were synthesized by adopting conventional melt quenching technique, Physical properties like density, molar volume, polaron radius, inter-ionic distance and field strength of the glass samples were investigated to assess the impact of Eu_2O_3. Optical and luminescence properties of the glasses were characterized with optical absorption, photoluminescence,X-ray induced emission spectra, temperature dependence emission spectra and decay times. Judd-Ofelt(JO) intensity parameters(Ω_λ) of the glasses were evaluated based on the absorption spectrum of 0.5 mol%. JO parameters, calculated from absorption spectra with thermal corrections on oscillator strength, were used to evaluate radiative properties such as radiative transition probability(A_R),branching ratio(β_R), stimulated cross section emission(σ) and radiative lifetime(τ_R) for ~5D_0→~7 F_J(J = 0,1,2,3 and 4) transitions. The decay rate of ~5D_0 fluorescent level for all the glass samples was single exponential. Lifetimes of the ~5D_0 level were decreased with increasing concentrations of Eu~(3+)ions from 0.05 mol% to 2.5 mol% which might be due to energy transfer through cross-relaxation in the glasses. The chromaticity coordinates(x, y) were similar for all BSYCaEu glasses and were located at the red region of CIE 1931 color chromaticity diagram. Hence, these results confirm that the Eu~(3+) doped BSYCaEu glasses could be useful for visible red lasers and glass scintillation applications.     

Synthesis and characterization of Ca0.9Mg0.1TiO3:Pr3+,Ag+ phosphor

Ca_(0.9)Mg_(0.1)TiO_3:Pr~(3+),Ag~+ phosphors were synthesized by solid-state reaction technique. The crystalline phase and luminescence performances of Ca_(0.9)Mg_(0.1)TiO_3:Pr~(3+),Ag~+ were observed by X-ray powder diffractometer(XRD), transmission electron microscope(TEM), photoluminescence spectrometer and brightness meter, respectively. The addition of Ag~+ can diminish in the crystal particle sizes of Ca_(0.9)Mg_(0.1)TiO_3:Pr~(3+). Because Ag+ can reduce the concentration of the undesirable defects in the phosphor, luminescence intensity of Ca_(0.9)Mg_(0.1)TiO_3:Pr~(3+),Ag~+ is 2.3 times as high as that of Ca_(0.9)Mg_(0.1)TiO_3:Pr~(3+)at the same preparation condition. The effect of Ag+ on the persistent afterglow properties is to deepen the energy storage traps and enhance the energy transfer efficiency from Ca_(0.9)Mg_(0.1)TiO_3 to Pr~(3+). The persistent afterglow properties of Ca_(0.9)Mg_(0.1)TiO_3:Pr~(3+),Ag~+ are better than those of Ca_(0.9)Mg_(0.1)TiO_3:Pr~(3+) at the same preparation condition. In conclusion,Ca_(0.9)Mg_(0.1)TiO_3:Pr~(3+),Ag~+ phosphor with molar ratio of Ag~+to Pr~(3+) 3:1 obtained at 900 ℃ for 4 h exhibits the optimal photoluminescence performances.     

1O2-activatable Eu3+-afterglow nanoprobe for highly sensitive detection of porphyria in whole blood

High-sensitivity detection of porphyrin in blood is very important for the early diagnosis and treatment of porphyria.Based on the advantages of longer luminescence lifetime and lower background interference,organic afterglow molecular porphyrin detection probes were developed,but these probes show poor water solubility and insufficient luminescence intensity.Herein,we present an afterglow nanoprobe(Eu-NP) for porphyria detection in whole blood.The luminescent substance(europium complex) and the...     

Effect of excitation wavelength (blue vs near UV) and dopant concentrations on afterglow and fast decay of persistent phosphor SrAl2O4:Eu2+,Dy3+

The persistent phosphor SrAl₂O₄:Eu²⁺,Dy³⁺ is the subject of numerous investigations. One often neglected aspect is that in this phosphor, as well as in Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺, there are two different Sr²⁺ sites which can be occupied by the dopant Eu²⁺ ions. We first introduce a general scheme of possible energy transfers in these persistent phosphor materials including explicitly both europium ions. This scheme is used as a generic starting point to study experimentally specific pathways. We illustrate this application with the study of the effect of excitation wavelength (444 and 382 nm) on the afterglow of differently doped SrAl₂O₄:Eu²⁺,Dy³⁺ samples, as well as on the emission decay curves. With the same excitation intensity under 444 nm excitation, the resulting afterglow intensity is stronger than under near UV excitation. At 382 nm, Eu²⁺ ions on both Sr²⁺ sites in SrAl₂O₄ are excited, but at room temperature the blue emission is quenched, leading to a loss of photons. The observed effects can further be associated with the ratio of Eu²⁺ ions and trap states which are modulated by the concentrations of Eu²⁺ and Dy³⁺ in SrAl₂O₄, as well as by temperature. Increasing the nominal Dy³⁺ content from 0.1 mol% to 0.5 mol% with respect to Sr results in the doubling of the integrated afterglow intensity and confirms thus that Dy³⁺ ions are indeed involved in the trapping process. The concentration of trap states is much lower than the concentration of Eu²⁺ ions, as even with low excitation densities, a plateau of integrated afterglow intensity (corresponding to the total number of accessible traps) is reached. We postulate that an important fraction of excited Eu²⁺ ions can potentially transfer their energy to trap states. Once that all traps are filled or in a dynamical filling-depletion process under illumination (with thermal and/or optical depletion processes), for the remaining Eu²⁺ a “normal” steady-state emission is observed. The luminescence decay curves at 520 nm measured at 77 K show a mono-exponential decay with a common lifetime of about 1140 ns for all 5 samples under 437 nm excitation, while under 375 nm excitation, a feed process originating from the energy transfer between Eu²⁺ ions is demonstrated. Under 375 nm excitation, the non-exponential decay observed at 440 nm can be quantitatively associated to a Förster energy transfer process with R₀ = 1.58 (8) nm. For the overall understanding of the afterglow processes, it appears that one has to consider the individual contributions of all active ions on different lattice sites.     

Blue-emitting Sr_(1-x)Ca_xLu_2O_4:Ce~(3+) phosphors for high CRI white LEDs

A broadband blue-emitting Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro perties,external quantum efficiency,the rmal stability and application perfo rmance of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+),by partially substituting Sr~(2+) with Ca~(2+)(x=0-0.2),were studied by various analytical techniques.When the Ca/Sr ratio of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) gradually increases,the emission peak of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) red-shiftes from 459 to 465 nm,corrected external quantum efficiency increases from 31.8% to 42.9%,and the thermal stability is also improved.The mechanism of the changes of the photoluminescence emission and excitation spectra,external quantum efficiency and thermal stability properties was also investigated in detail.In addition,a w-LED was fabricated by using SrLu_2 O_4:Ce~(3+)(blue),β-sialon:Eu~(2+)(green) and(Sr,Ca)AlSiN_3:Eu~(2+)(red) phosphors combined with a 405 nm near-UV LED chip,and its color rendering index(CRI) reaches 96.0.When Sr_(0.8)Ca_(0.2)Lu_2 O_4:Ce~(3+)is applied as blue phosphor to substitute SrLu_2 O_4:Ce~(3+),the obtained w-LED devices have high luminous efficiency,and CRI greater than 95.0.These re sults show that the Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.     

Effects of Annealing Treatments on Luminescence and Scintillation Properties of Ce：Lu3 Al5 O12 Crystal Grown by Czochralski Method

Lu3Al5O12 single crystals grown in pure N2 atmosphere by Czochralski method were annealed in oxidizing atmosphere （air）and reducing atmosphere （H2 ＋ N2）, respectively. Effects of annealing treatments on luminescence and scintillation properties of the crystals were investigated. The crystal annealed in air showed the highest luminescence intensity under blue light or vacuum ultraviolet excitation in comparison with that annealed in reducing flux or the as-grown crystal. Under X-ray excitation, crystal annealed in reducing atmosphere had the lowest light yield, and crystal annealed in air had the fastest decay time under ^137Cs 662 keV γ-ray excitation. Different annealing treatments resulted in different luminescence and scintillation properties, which might related with oxygen vacancies or defect existing in the crystals.     

Enhanced afterglow performance of CaAl_2O_4:Eu~(2+),Nd~(3+) phosphors by co-doping Gd~(3+)

In order to effectively improve the afterglow properties of CaAl_2 O_4:Eu~(2+),Nd~(3+) phosphors,a series of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)(x=0,0.012,0.024,0.036,0.048,0.060 mol) phosphors were prepared by a high-temperature solid-phase approach.Crystalline composition and microstructure were characterized by XRD,TEM,HRTEM,and XPS,luminescence properties were systematically analyzed by fluorescence spectra,afterglow decay curves and TL glow curve.Results show that all of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)phosphors belong to monoclinic CaAl_2 O_4,without other cystalline phase.The blue emission at 442 nm is observed,which is assigned to the 4 f~65 d→4 f~7 transition of Eu~(2+) ions.Doping with appropriate amount of Gd~(3+) ions(x=0.036 mol) significantly improves the afterglow properties of phosphors,but the excessive doping of Gd~(3+) induces the fluorescent quenching.The doping of moderate Gd3+changes the traps states,the trap depth varies from 0.598 to 0.644 eV and the trap concentration is also greatly improved,thus significantly improving afterglow performance.     

Shape control over microwave hydrothermally grown Y2O3:Eu by europium concentration adjustment

Two-step synthesis of Y2〇3:Eu nanostructures was performed. It includes microwave driven hydrothermal and calcination stages. Performed route results in crystallization of Y4〇(OH)g(N〇3):Eu crystals initially, then Y2〇3:Eu crystals after calcination. Arranged Eu contents in relation to overall cation quantity were set to 2 mol%, 10 mol% and 20 mol%. Varying europium concentrations influence habit of obtained Y4〇(OH)g(N〇3):Eu crystals from needle-like to plate-like and as a result, also shapes of final Y2〇3:Eu nanostructures. Additionally, certain amount of Eu2+ ions was detected in as-grown material using laser spectroscopy and decay kinetics measurements. Obtained material was calcined at 1200 °C in the air, which results in oxidation of Eu2+ ions and crystallization of small number of cubic EU2 O3 nanocrystals. Characterization of obtained materials was performed using XRD, SEM, TEM, EDX, CL,Raman and photoluminescence spectroscopy.     

Bi3+ assisted luminescence in SrMoO4:Sm3+ red phosphors

In this paper, we report synthesis of pure SrMoO₄, Sm³⁺ (1 at%–5 at%) doped SrMoO₄ and Bi³⁺ (1 at%–3 at%) co-doped in 4 at% Sm³⁺ doped SrMoO₄ (SrMoO₄:4Sm³⁺) phosphors by solution combustion method. The X-ray diffraction (XRD) analysis reveals the tetragonal phase of all samples, also Bi³⁺ co-doping supports crystallite size growth and reduces lattice strain. Absorption analysis of Sm³⁺ doped SrMoO₄ ascertains a decrease in band gap and Bi³⁺ co-doping confirms the emergence of an absorbance peak at around 308 nm attributed to Bi³⁺ energy levels. Photoluminescence (PL) analysis ascertains an increase in emission peaks for Sm³⁺ doped SrMoO₄ up to 4% concentration, which are attributed to an electron transition from ⁴G_5/2 to ⁶H_J (J = 5/2, 7/2, 9/2, and 11/2) energy levels of Sm³⁺ ions. We have explained the effects of Bi³⁺ co-doping on the luminescence of Sm³⁺ doped SrMoO₄. The reduced microstrain and increased crystallinity of the phosphors as a result of Bi³⁺ co-doping and their correlation with the luminescence of Sm³⁺ ions are discussed.     

Single-phase white-emitting and tunable color phosphor Na3Sc2(PO4)3:Eu2+,Dy3+: Synthesis,luminescence and energy transfer

A series of Eu²⁺/Dy³⁺ single doped and co-doped Na₃Sc₂(PO₄)₃ phosphors were synthesized by the high-temperature solid-state method, and their phase, morphology, and luminescence properties were characterized. Under the excitation of 370 nm, the Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor can emit white light whose spectrum is composed of a broad emission band centered at 460 nm and the other three peaks at 483, 577, and 672 nm, respectively. There is energy transfer from Eu²⁺ to Dy³⁺ ion in Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor due to the good overlap between the emission spectrum of Na₃Sc₂(PO₄)₃:Eu²⁺ and the excitation spectrum of Na₃Sc₂(PO₄)₃:Dy³⁺, which is further confirmed by the fluorescence lifetime decrease of Eu²⁺ ion with the increase of Dy³⁺ concentration. The process of energy transfer is via dipole–quadruple interaction which is confirmed by applying Dexter's theory. By increasing the Dy³⁺ concentration, the color coordinates of the Na₃Sc₂(PO₄)₃:0.01Eu²⁺,xDy³⁺ phosphors can be adjusted from blue to white, and then to yellow. The optimized concentration of Dy³⁺ ions is 4.0 mol%, beyond which the concentration quenching will take place. The Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor shows fairly good resistance to thermal quenching behavior, of which the emission intensity at 423 K can maintain 90.3% of the initial value (298 K). These results suggest that the Na₃Sc₂(PO₄)₃:0.01Eu²⁺,xDy³⁺ phosphors have potential applications as the color-tunable or a single-phase white emitting phosphor in white LEDs.