Electrospinning synthesis and luminescent properties of Lu₂O₃:Eu³⁺ nanofibers

One-dimensional Lu2O3:Eu3+ nanofibers were prepared by electrospinning followed by high-temperature calcinations.Thermogravimetric and differential thermal analysis,X-ray powder diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy,photoluminescent spectra and decay curves were used to characterize the samples.Results showed that samples began to crystallize at ～500 oC and crystallized completely around 1000 oC.The average diameter of nanofibers(1000 oC annealed) was about 55 nm and the particle size of Lu2O3:Eu3+ increased with increasing annealing temperature.Under ultraviolet excitation,nanofibers exhibited typical red emission of Eu3+ in Lu2O3.The effect of heat-treatment temperature on luminescent properties of nanofibers was also discussed.     

Preparation and photoluminescence of Eu-doped oxyfluoride borosilicate glass ceramics

Eu-doped transparent oxyfluoride borosilicate glass ceramics containing Ba2GdF7 nanocrystals were prepared by controlling crys-tallization of melt-quenched glass fabricated under a reductive atmosphere.In the oxyfluoride borosilicate glass ceramics,the mean crystal size of Ba2GdF7 nanocrystals was about 30 nm,which could be observed by X-ray diffraction(XRD) and transmission electron microscopy analysis.The photoluminescence spectra of the samples excited at 392 nm showed that,besides the characteristic sharp emissions of Eu3+ ions,a very intense broadband emission of Eu2+ ions centered at 450 nm appeared.The photoluminescence intensity of Eu3+ and Eu2+ ions in the glass ceramics was much stronger than that in the as-made precursor.The long decay lifetimes of Eu3+ and Eu2+ ions evidenced the partitions of Eu3+ and Eu2+ ions into the Ba2GdF7 nanocrystals.The energy transfer from Gd3+ ions to Eu3+ and Eu2+ ions was confirmed by the excita-tion and emission spectra.     

Luminescent properties of Eu~（3＋） doped Gd_2WO_6 and Gd_2（WO_4）_3 nanophosphors prepared via co-precipitation method

Eu3+ doped Gd2WO6 and Gd2(WO4)3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The emission spectra and excitation spectra of samples were measured. J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated, and the concentration quenching of Eu3+ luminescence in different matrixes were studied. The results indicated that effective Eu3+:5D0-7F2 red luminescence could be achieved while excited by 395 nm near-UV light and 465 nm blue light in Gd2WO6 host, which was similar to the familiar Gd2(WO4)3:Eu. Therefore, the Gd2WO6:Eu red phosphors might have a potential application for white LED.     

Luminescent polymer electrolytes based on chitosan and containing europium triflate

Solid polymer electrolytes based on chitosan and europium triflate were prepared by solvent casting and characterized by X-ray diffraction, scanning electron microscopy(SEM), atomic force microscopy(AFM), and photoluminescence spectroscopy. The X-ray diffraction exhibited that the samples were essentially amorphous with organized regions over the whole range of the salt content studied. The AFM analysis demonstrated that the smoother sample had roughness of 4.39 nm. Surface visualization through SEM revealed good homogeneity without any phase separation for more conductive samples and the less conductive showed some imperfections on the surface. The emission and excitation spectra displayed the characteristic bands of Eu(CF_3SO_3)_3 in addition to broad bands corresponding to the polymer host. The excited state ~5D_0 lifetime values ranged from 0.29–0.37 ms for the studied samples.     

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.     

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.     

Preparation and photoluminescence enhancement of Li＋ and Eu3＋ co-doped YPO4 hollow microspheres

Li+ and Eu3+ co-doped YPO4 hollow microspheres were successfully synthesized by a sacrificial template method using polystyrene (PS) as template. Techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as transmission electron microscopy (TEM) were employed to characterize the as-synthesized sample. Furthermore, the photoluminescence (PL) characterization of the Li+ and Eu3+ co-doped YPO4 microsphere was carried out and the effects of the doping concentration of Li+ and Eu3+ active center concentration as well as calcination temperature on the PL properties were studied in detail. The results showed that the incorporation of Li+ ions into the YPO4 :Eu3+ lattice could induce a remarkable improvement of the PL intensity. The highest emission intensity was observed with the compound of 5%Li+ and 5%Eu3+ co-doped YPO4 , whose brightness was increased by a factor of more than 2.2 in comparison with that of the YPO4 :5%Eu3+.     

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.     

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.     

Synthesis of CaWO4：Eu3＋ phosphor powders via ethylene glycol route and its optical properties

Eu3+ doped CaWO4 with tetragonal system were prepared at comparatively low temperature (125 ?C) in ethylene glycol medium. The phosphor was further investigated by X-ray diffractometer (XRD), photoluminescence spectrophotometer (PL), Fourier transform infra red (FT-IR) spectroscopy and transmission electron microscopy (TEM). XRD analysis indicated a decrease in the unit cell volume of CaWO4 with increasing Eu3+ ion concentration. It indicated the homogeneous substitution of Ca2+ ions in CaWO4 by the Eu3+ ions. TEM images showed that the particle size ranged from 20 to 200 nm and it could extend the application of the nanoparticles. The photoluminescence study showed that the intensity of electric dipole transition (5D0→7F2) at 614 nm dominated over the magnetic dipole transition (5D0→7F1) at 592 nm. The optimum concentration of Eu3+ for the highest luminescence was found to be 20 at.%. The as prepared samples were found to be dis-persible in water and methanol.     

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...     

Preparation and Characterization of Sol-Gel Derived Au Nanoparticle Dispersed Y2O3：Eu Films

Gold nanoparticles dispersed Y2O3 films were prepared through a sol-gel method by using yttrium acetate and Au nanoparticles colloid as precursors. The films were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and UV-VIS absorption spectra. XRD patterns and TEM images of Y2O3 ＋ Au films give the same resuits on structure and particle size as that of pure Y2O3 films. The surface plasma resonance （SPR） of Au nanoparticles in Y2O3 ＋ Au film was observed around 550 nm in the absorption spectrum and its position shifts to red with increasing annealing temperature is caused by the increase of dielectric constant of Y2O3 matrix and the size of Au nanoparticles. The second and third order nonlinear optical effects of Y2O3 ＋ Au films were also observed. The photoluminescent properties of Y2O3 ： Eu ＋ Au films were investigated and results indicate that there exist an energy transfer from Eu^3 ＋ to Au nanoparticles and this energy transfer decreases the emission of Eu^3 ＋ in Y2O3 ： Eu ＋ Au film.     

Blue-green BaAl_2O_4：Eu~（2＋）,Dy~（3＋） phosphors synthesized via combustion synthesis method assisted by microwave irradiation

Blue-green luminescent BaAl2O4:Eu2+,Dy3+ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The XRD results revealed that when the concentration of urea was over 3 times higher than theoretical quantities, a BaAl2O4 single hexagonal phase was obtained. The SEM results revealed that the surface of the BaAl2O4:Eu2+,Dy3+ pow...     

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.     

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 ...     

Influence of concentration and sintering temperature on luminescence properties of Eu^3＋：SnO2 nanocrystallites

The nanopowders of SnO2 doped with different Eu3+ concentrations were synthesized using the modified Pechini method. The Eu3+ concentrations were high above solubility limit. The average size of crystallites was controlled by the sintering temperatures. The structure and the morphology of obtained powders were examined using the XRD (X-ray diffraction) and TEM (transmission electron microscopy) analyses. The Eu2Sn2O7 phase separation was observed at relatively high concentration of Eu3+ ions. The ZnS:Ag micropowders were mixed with the Eu3+:SnO2 powders and their normalized emission was used to measure a relative efficiency of Eu3+:SnO2. The photoluminescence spectra of mixed powders were measured in function of Eu3+ concentration and average size of nanocrystallites. The reference peak method was used for comparison of intensities of the samples and selection of optimal one. The influence of the average grain size and Eu3+ concen-tration on the phosphor’s efficiency was discussed. The presented results confirmed the rightness of synthesis of the Eu3+:SnO2 in form of nanocrystalites with relatively high Eu3+ concentration.     

High quality thin film phosphors of Y2O3:Eu3+ deposited via chemical bath deposition

High transparency in visible region was required for red-light-emitting Y2O3:Eu3+ thin film phosphors. Such films were obtained via chemical bath deposition on bare SiO2 glass substrates through heterogeneous nucleation with further heat treatment. Thin amorphous yttrium basic carbonate films could be completely transformed to crystalline Y2O3 at 650 °C. X-ray diffraction and field-emission scanning electron microscopy were used to characterize these products. The deposition temperature and the post-anneali...     

Infrared spectroscopy analyses of air-CH4 or air-CO gas flows interacting with polycrystalline CeO2, La2O3 and Lu2O3 oxides

A comparative study of reactivity between air-CH4 or air-CO gas flows and CeO2, La2O3 and Lu2O3 rare earth oxides was performed using Fourier transform infrared spectroscopy analyses of CO2 gas resulted from the conversion of CH4 or CO gases. Polycrystalline samples of CeO2, La2O3 and Lu2O3 were first prepared by specific precipitation methods followed by low temperature calcination process. In the case of Lu2O3 oxide, a new specific route was proposed. Crystallite dimensions were determined by X-ray diffraction and transmission electron microscopy analyses. Morphologies were characterized using scanning electron microscopy. Specific surface areas were determined from Brunauer-Emmett-Teller (BET) technique. Using infrared spectroscopy analyses, the conversion rates of CH4 or CO into CO2 were determined from the evolutions of CO2 vibrational band intensities, as a function of time and temperature. It was clearly established that, despite its low specific surface, the Lu2O3 oxide presented the highest capacity of conversion of CH4 or CO into CO2.     

Raman spectra of RE2O3 （RE=Eu,Gd, Dy,Ho, Er,Tm, Yb,Lu, Sc and Y）：laser-excited luminescence and trace impurity analysis

Raman spectra of a series of cubic rare earth sesquioxides RE2O3 （RE=Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y） were investigated by Raman spectroscopy with both 532 and 785 nm laser lines. Abundant additional bands due to laser-excited lumines-cence were observed. For Eu2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3, the luminescence mainly came from the intrinsic trivalent lanthanide ions, while for Gd2O3, Lu2O3, Sc2O3 and Y2O3, their luminescence were attributed to the trace impurities of other lumines-cent lanthanide ions such as Eu3＋, Nd3＋and Er3＋. This investigation confirmed Raman spectroscopy as a useful tool for detecting trace luminescent lanthanide impurities.