Synthesis and luminescence properties of SrAleO4：Eue＋,Dy3＋ hollow microspheres via a solvothermal co-precipitation method

SrAl2O4:Eu2+,Dy3+ hollow microspheres were successfully prepared through a facile and mild solvothermal co-precipitation combining with a postcalcining process.The structure and particle morphology were investigated by X-ray diffraction(XRD),scanning and transmission electron microscopy(SEM and TEM)pictures,respectively.The mechanism for the formation of spherical SrAl2O4:Eu2+,Dy3+ phosphor was preliminary presented.After being irradiated with ultraviolet(UV)light,the spherical phosphor emitted long-lasting green phosphorescence.Both the photoluminescence(PL)spectra and luminance decay,compared with that of commercial bulky powders,revealed that the phosphors had efficient luminescent and long lasting properties.It was considered that the SrAl2O4:Eu2+,Dy3+ hollow microspheres had promising long-lasting phosphorescence with potential scale-dependent applications in photonic devices.     

Preparation and characterization of flower-like SrAl2O4:Eu2+,Dy3+ phosphors by sol-gel process

A flower-like Eu2+ and Dy3+ co-doped SrAl2O4 long-lasting phosphorescent (LLP) phosphor was synthesized via the inorganic- salt-based sol-gel method.The crystal structure,morphology and optical properties of the composite were characterized.X-ray diffraction diffu-sion (XRD) data and DSC-TG curves of the phosphor revealed that the SrAl2O4 crystallites have been formed after the precursor was calcined at 900 °C and to be single-phase SrAl2O4 at 1100 °C.The SEM photographs indicated that the sample exhibited ...     

Preparation and photoluminescence of Tb^3＋ doped SrAl2O4 phosphor by composite combustion method

High-efficient Tb^3＋ activated SrAl2O4 phosphor was synthesized by a combined combustion-solid-state reaction method. The precursor of SrAl2O4：Th^3＋ phosphor was prepared via a combustion process, and then the as-prepared powder was heated in a reductive ambient of activated carbon at 1250 ℃ for 1 h. The results of X-ray diffraction, scanning electron microscopy, and photoluminescence spectra revealed the influence of the dosage of urea and heated process on the crystallinity, morphology, and photoluminescence of the phosphor. Comparing with traditional solid-sate reaction, the crystallinity and emission intensity of the SrAl2O4：Tb^3＋ phosphor were improved by this two-step process.     

Combustion synthesis,characterization and luminescence properties of barium aluminate phosphor

The blue-green emitting Eu2+ and Nd3+ doped polycrystalline barium aluminate(BaAl2O4:Eu2+,Nd3+) phosphor, was prepared by a solution-combustion method at 500 oC without a post-annealing process. The characteristic variation in the structural and luminescence properties of the as-prepared samples was evaluated with regards to a change in the Ba/Al molar ratio from 0.1:1 to 1.4:1. The morphologies and the phase structures of the products were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS), while the optical properties were investigated using ultra-violet(UV) and photoluminescence(PL) spectroscopy, respectively. The XRD and TEM results revealed that the average crystallite size of the BaAl2O4:Eu2+,Nd3+ phosphor was about 70 nm. The broad-band UV-excited luminescence of the phosphors was observed at λmax=500 nm due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion. The PL results indicated that the main peaks in the emission and excitation spectrum of phosphor particles slightly shifted to the short wavelength due to the changes in the crystal field due to the structure changes caused by the variation in the quantity of the Ba ions in the host lattice.     

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

Ba0.9-ySryAl12O19:Eu0.1 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 Ba0.9-ySryAl12O19:Eu0.1 strengthened and blue-shifted.     

Eu2＋ and Dy3＋ codoped （Ca,Sr）7（SiO3）6Cl2 highly efficient yellow phosphor

Eu2+ and Dy3+ codoped(Ca,Sr)7(SiO3)6Cl2 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and photoluminescence spectra. The as-prepared phosphor showed a broad emission spectrum centered at 550 nm for Eu2+single-doped phosphor, while located at 548–544 nm for the Eu2+, Dy3+ codoped samples under excitation at 380 nm light. The emission intensity was greatly improved when Dy3+ was doped into the(Ca,Sr)7(SiO3)6Cl2:Eu2+ system. The composition-optimized sample with 3 mol.% of Dy3+ and constant 10 mol.% of Eu2+ exhibited a 220% PL enhancement compared to the phosphor with 10 mol.% Eu2+ single-doped. Meanwhile, it was found that the quantum efficiency of phosphor namely(Ca,Sr)7(SiO3)6Cl2:3 mol.% Dy3+, 10 mol.% Eu2+ could get up to 24.6%. The synthesized yellow-emitting(Ca,Sr)7(SiO3)6Cl2:Dy3+,Eu2+ is a promising candidate as high-efficiency yellow phosphor for NUV-excited white LEDs.     

Synthesis,structural and optical properties of SrZrO3：Eu3＋phosphor

Eu3+ activated Sr1–xEuxZrO3(x=0.01–0.04) phosphor with perovskite structure was successfully synthesized by using combustion method.The structure,morphology and optical properties of the material were characterized by X-ray diffraction,scanning electron microscopy and fluorescence spectrometry.The XRD results indicated that crystals of SrZrO3:Eu3+ belongs to tetragonal perovskite system.The phosphor could be effectively excited by UV light and the emission spectra results indicated that reddish-orange luminescence of SrZrO3:Eu3+ due to magnetic dipole transition 5D0→7F1 at 593 nm was dominant.Thus,the prepared phosphor showed remarkable luminescent properties which find applications in field emission display(FED) and plasma display panel(PDP) devices.     

Investigation on luminescence properties of Ln^3＋ doped Sr3EuMgSi2O8 （Ln=Dy, Er, Ho）

The luminescent properties of Sr2.97MgSi2O8:Eu2+0.01 phosphors were investigated with different Ln3+0.02(Ln3+:Dy3+,Er3+,Ho3+) co-dopants. The co-dopants had no influence on both the structure of the lattice and the position of the emission peak. However, the afterglow properties of samples were enhanced with different co-dopants. The afterglow duration of the Dy3+ co-doped sample was longer than that of the others. Furthermore, the co-doping samples had stronger thermoluminescence (TL) intensity and therefore longer afterglow duration. At last, the self-reduction of Eu3+→Eu2+ was observed in an silicate compound of Sr3-xMgSi2O8:xEu phosphor in air condition. This is the first time to show a blue long afterglow phosphor synthesized avoiding reducing atmosphere.     

Characterization and photoluminescence of Lu_2O_3-Eu~（3＋） nano-phosphor prepared by modified solution combustion method

Nanoscale Lu2O3:Eu3+ phosphor was prepared by a modified solution combustion method using urea and acrylamide monomer.The particle sizes and photoluminescent properties of nano-phosphor were closely related to the molar ratio of urea-to-RE nitrates and acrylamide monomer-to-RE nitrates.The as-prepared samples with the sizes of 9.6-11.6 nm were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy and energy dispersive spectrometer.Lu2O3:Eu3+ nano-phosphor that depicted high photoluminescence in the size around 10 nm was reported.Compared with the sample prepared by solid state reaction,the photoluminescence of sample was increased sufficiently to be 45.1%.The emission spectra of the samples presented the typical emission from 5D0 level to 7FJ(J=0,1,2,3,4) level of the Eu3+ ion.     

Effect of MgF2-H3BO3 flux on the properties of (Ce,Tb)MgAl11O19 phosphor

The green-emitting(Ce,Tb)MgAl11O19(CTMA) phosphor was prepared by the conventional high temperature solid-state reaction method.The effect of fluxes on the crystal structure,particle morphology,size distribution and photoluminescence properties of CTMA phosphor was investigated by means of the X-ray powder diffraction,scanning electron microscopy and photoluminescence spectrum.The results showed that the addition of appropriate amount of MgF2-H3BO3 flux improved the phase purity of CTMA phosphor,and influen...     

Synthesis and characterization of CaAl_xO_y:Eu²⁺ phosphors prepared using solution-combustion method

Europium-doped calcium aluminate(CaAlxOy:Eu2+) phosphors were obtained at low temperatures(500 oC) by the solution-combustion of corresponding metal nitrate-urea solution mixtures.The particle size and morphology and the structural and luminescent properties of the as-synthesized phosphors were examined by means of scanning electron microscopy(SEM),X-ray diffraction(XRD),Auger spectroscopy,transmission electron spectroscopy(TEM) and photoluminescence(PL).It was found that the Ca:Al molar ratios showed greatly influence not only on the particle size and morphology,but also on their PL spectra and structure.With the Ca:Al molar ratios increasing from 6:100 to 26:100,the structure of as-synthesized phosphor changed from CaAl12O19 to monoclinic CaAl2O4 and the dominant emitting light from red to blue,implying that the oxidation state of doped europium ions changed from trivalent to divalent due to the structure variation of host lattice.A blue phosphor with almost pure phase can be easily prepared by solution combustion method with suitable Ca:Al molar ratio.     

Synthesis of Dy2O3 nanoparticles via hydroxide precipitation： effect of calcination temperature

This work described the preparation of dysprosium oxide, Dy2O3, nanoparticles using the homogeneous precipitation method. Dy3+ ions were precipitated using NaOH solution. The obtained product was filtered, dried, and then calcined for 1 h at the temperature range of 300–700 °C in static air. The calcination temperature of the Dy-precursor was chosen based on its decomposition as indicated by the TGA analysis. The crystalline structure and surface morphology of the calcined solids were studied by X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). The obtained results revealed that Dy2O3 with crystallites size of 11–21 nm was formed at 500 °C. Such value increased to 25–37 nm for the sample calcined at 700 °C.     

Sol-gel synthesis and photoluminescence properties of BaSO_4/Y_2O_3:Eu~(3+) core-shell submicrospheres

Europium-doped nanocrystalline Y2O3 phosphor layers were coated on the surface of preformed submicron BaSO4 spheres via the sol-gel process.The obtained BaSO4/Y2O3:Eu3+ core-shell phosphors were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive spectroscopy(EDS) and photoluminescence spectra.The results showed that the obtained BaSO4/Y2O3:Eu3+ core-shell phosphors consisted of well-dispersed submicron spherical particles with na...     

Combustion synthesis and luminescence properties of blue NaBaPO4:Eu2+ phosphor

The blue-emitting phosphor NaBaPO4:Eu2+ was prepared by the combustion method. The phase structure and microstructure of the as-prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Under the excita-tion wavelength of 360 nm, the emission spectrum exhibited only one blue band centering at 435 nm, which was ascribed to the 4f65d1→4f7 transition on Eu2+ ions. Compared with the phosphor obtained by solid-state reaction method, the relative emission intensity of sample ob-tained by combustion method increased slightly. The decay times and the temperature dependence luminescence intensities (25-300 oC) were discussed in order to further investigate the potential applications. Furthermore, Eu2+-doped NaBaPO4 phosphor showed higher thermally sta-ble luminescence comparable to commercially available Y3Al5O12:Ce3+ (YAG:Ce3+) phosphor. All the investigated suggestions that Na-BaPO4:Eu2+ is a good phosphor candidate applied in white light emitting diode.     

Nano-preparation promoting effectively luminescent properties of one-dimensional rare earth oxides

Rare earth (La,Nd and Tb) oxides with one-dimensional micro/nanostructures were synthesized hydrothermally under facile and mild conditions with two surfactants, and characterized by X-ray diffraction (XRD), thermal gravimetry (TG), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence. The results showed that the synthesized rare earth oxides behaved regular nano-and micro-scale structures. And the morphologies of samples depended on the radii of rare earth ions, with the help of two surfactants of sodium dodecyl sulfonic and PEG 600. Nanocrystalline La2O3:Eu3+ possessed good photoluminescence (PL) property and might be used as a nanosized phosphor, its PL intensity was altered by the doping Eu3+ concentration and the optimum concentration of Eu3+ was 3 mol.%. In comparison with bulk Eu3+/La2O3, Eu3+/nano-La2O3 showed better photoluminescence property, nearly equal to that of nanocrtstal-line La2O3:Eu3+. Tb4O7 microwires showed interesting photoluminescence properties.     

Synthesis and luminescence properties of bluish-green emitting K2MgSi3O8:Eu2+ phosphor

Eu2+-doped K2 Mg Si3O8 phosphors were synthesized by conventional solid-state reaction method. The phase formation of as-prepared samples was characterized by X-ray powder diffraction. The luminescence properties were investigated by the photoluminescence excitation and emission spectra, decay curve and CIE coordinates. The phosphor showed bluish-green emission centered at 460 nm under the excitation of UV and near UV light with the wavelength range of 250–430 nm. Two Eu2+ emission centers existed in the K2 Mg Si3O8:Eu2+ phosphor according to the luminescence spectra and the decay curves. The critical quenching concentration of Eu2+ doping was determined to be 3.0 mol.% and the concentration quenching mechanism was dipole-dipole interactions between Eu2+ ions. These results suggested that K2 Mg Si3O8:Eu2+ was a potential bluish-green phosphor candidate for white UV-LED.     

Preparation and Luminescence Properties of Y2O3:Eu3+ Nanorods via Post Annealing Process

Yttrium oxide doped with europium has a great prospective for FED and PDP phosphor application. In present study, the precursor of yttrium oxide hydroxide nitrate nanorod, which was prepared via hydrothermal reaction route using PEG-6000 as template from the starting Y(NO3)3 and KOH reactant system, was used to prepare Y2O3:Eu3 nanorod via a post annealing process during which the precursor with adjustable shape and size was transformed to final Y2O3:Eu3 product. XRD, field emission scanning electron microscopy (FE-SEM) and photoluminescence spectra (PL) were used to characterize the crystalline, morphology and luminescence properties of as-formed Y2O3:Eu3 products synthesized at different post annealing temperatures, respectively. The results indicate that grain morphology of obtained Y2O3:Eu3 product was nanorod with a mean diameter of about 40～60 nm and length of about 500～700 nm, the nanorod structure and morphology of obtained Y2O3:Eu3 product maintained during post annealing process and the size varied slightly with different annealing temperatures. Pure cubic Y2O3:Eu3 phase was formed and the size was the smallest at annealing treatment of 500 ℃. Under the annealing temperature below 500 ℃ its diameter increased with increasing annealing temperature, and remained in a stable size when the annealing temperature was above 500 ℃. The PL spectra of excitation spectra of Y2O3:Eu3 product show that it exhibits excitation band located at about 395 and 468 nm, respectively. Above two excitation bands could be ascribed to the transition 4f-4f of Eu3 ions in the Y2O3 host. On the other hand, the main emission peaks of the as-prepared products could be ascribed to the Eu3 ions transition from 5D0 to 7F2. Furthermore, the luminescent intensity was improved about three times when the annealing temperature increased from 500 to 1000 ℃.     

Influence of dispersant on Y_2O_3:Eu~(3+) powders synthesized by combustion method

Y2O3:Eu3+ powders were synthesized by combustion method and the influence of dispersant was investigated.XRD analysis indicated that the particle size increased with a small amount of dispersant firstly and then decreased with a further increase of dispersant.The morphologies of the powders were studied by scanning electron microscopy(SEM) and high-resolution transmission electron microscopy(HRTEM).SEM images revealed that an appropriate amount of dispersant could reduce the agglomeration significantly.Due ...     

Experimental and theoretical analysis on the charge transfer band of Y_2O_3:Eu nanocrystals

Nanocrystalline cubic Y2O3:Eu were prepared by combustion reaction.The crystal structure and morphology were analyzed by means of X-ray diffraction(XRD) and transmission electron microscopy(TEM).The luminescent properties of the powder were investigated.The charge transfer band position showed redshift from 241 to 251 nm,which was related to the change of the local surroundings of Eu3+ ions in nanocrystalline Y2O3:Eu.The ground-state electronic structure and charge transfer transition of both the bulk and nanocrystalline cubic Y2O3:Eu crystals were calculated by the ab initio self-consistent relativistic DV-Xα(discrete variational Xα) method.A complete 35-ion cluster was selected to simulate the local coordination surroundings of Eu doped in Y2O3 bulk crystals while five additional incomplete clusters were also selected to simulate the local surroundings of Eu ions in nanocrystals.It could be found that the charge transfer energies of the nanocrystalline Y2O3:Eu were less than that of the bulk counterpart,which was consistent with the redshift phenomenon of the CT band in the excitation spectrum of the nanocrystalline Y2O3:Eu.     

Structure and luminescent properties of luminous polypropylene fiber based on Sr_2MgSi_2O_7:Eu~(2+),Dy~(3+)

The luminous polypropylene fiber based on long afterglow luminescent material Sr2MgSi2O7:Eu2+,Dy3+ was prepared by melt-spinning process. Micro-morphology, phase composition, crystal structure, spectral features and afterglow properties of the luminescent fiber were tested and analyzed. The results indicated that the fiber had independent superposition phase features of both Sr2MgSi2O7:Eu2+,Dy3+ and polypropylene. The range of its excitation wavelength was located between 250–450 nm; therefore, the luminescent fiber could be excited by ultraviolet or visible light. It could emit blue light of 460 nm wavelength after excitation, which was caused by the 5d-4f transition of Eu2+ ions within the host lattice. The initial luminescent intensity was more than 0.8 cd/m2, and afterglow life lasted 7 h. The afterglow decay was composed of rapid-decaying and slow-decaying processes, and the decay characteristics depended on the depth and concentration of trap level in the Sr2MgSi2O7:Eu2+,Dy3+.