Synthesis and characterization of needle-like BaAleO4：Eu,Dy phosphor via hydrothermal-homogeneous precipitation method

A needle-like Eu2+ and Dy3+ co-doped BaAl2O4 long-lasting phosphor was synthesized via a hydrothermal-homogeneous precipitation method assisted by cetyl trimethyl ammonium bromide(CTAB) as a template.The crystal structure,morphology and optical properties of the composites were characterized.XRD results showed that the single-phase BaAl2O4 was formed at 900 ℃ in an active carbon atmosphere,which was much lower than that prepared by traditional solid-state reaction method.Scanning electron microscopy(SEM) and transmission electron microscopy(TEM) observation revealed that the precursor had well-dispersed distribution and showed needle-like morphology with the average diameter of about 100 nm and the length up to 1 μm.The final product,BaAl2O4:Eu2+,Dy3+ phosphor,inherited the needle-like shape from precursor via adding the surfactant CTAB.After irradiation by ultraviolet radiation with 355 nm for 5 min,the phosphors emitted bluish green color long-lasting phosphorescence corresponding to the typical emission of Eu2+ ion.Both the photoluminescence spectra and luminance decay revealed that the phosphor had efficient luminescent and long-lasting properties.     

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.     

Synthesis and luminescence properties of a novel red Sr3Bi（PO4）3：Sm^3＋ phosphor

A series of Sr3Bi1-x(PO4)3: xSm3+phosphors were prepared by solid state method at 1250 °C for 4 h. X-ray diffraction (XRD) indi-cated that the sample was of a pure phase of Sr3Bi(PO4)3. The main excitation peaks were located at 343 (6H5/2→4H9/2), 360 (6H5/2→4D3/2), 373 (6H5/2→6P7/2), 400 (6H5/2→4F7/2), 414 (6H5/2→6P5/2) and 467 nm (6H5/2→4I13/2). The main emission were located at 563 (4G5/2→6H5/2), 599 (4G5/2→6H7/2), 646 (4G5/2→6H9/2) and 708 nm (4G5/2→6H11/2). The intensest emission was excited by 400 nm. We studied the effect of differ-ent doping concentrations of Sm3+ activator on the luminescence properties and found that the luminescent intensity first increased with Sm3+ concentration increasing, and then decreased. The luminescent intensity had the best value when x=0.04. The chromaticity coordinates of the sample Sr3Bi0.96(PO4)3:0.04Sm3+ were (x=0.57, y=0.36), and the lifetime was 2.12 ms.     

Luminescence properties of SrB4O7：Sm^2＋ for light conversion agent

A deep red-emitting SrB4O7:Sm2+ phosphor for light conversion agent was synthesized by the conventional solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the phase formation of SrB4O 7:Sm2+ materials. Results of luminescence properties showed that the phosphor could be efficiently excited by the UV-vis light region from 250-500 nm, and it exhibited deep red (685 nm) emission corresponding to 5D0 → 7F0 transition of Sm 2+ . The critical quenching concentration of Sm 2+ in SrB4O7 :Sm 2+ phosphor was about 0.05, and the corresponding concentration quenching mechanism was verified to be the dipole-dipole interaction according to the Dexter’s theory. The decay times had few alterations with different concentrations in SrB4O7:xSm 2+ phosphor.     

Synthesis and luminescence properties of BaWO4：Pr^3＋ microcrystal

BaWO4:Pr3+ (hereafter BWO:Pr) microcrystals were prepared via a hydrothermal route, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence excitation and emission spectra. The as-prepared products with different morphologies of egg-shape rod, olive-like, and quasi-sphere were obtained by the addition of the surfactants and chelating agents. The emis-sion spectra of BWO:Pr microcrystals showed the strong red emission (642 nm) assigned to the Pr3+ ions of 3P0→3F2 transition with blue ex-citation (484.6 nm, 3H4→3P0).     

Effect of gadolinium incorporation on optical characteristics of YNbO_4：Eu~（3＋） phosphors for lamp applications

Eu3+-doped (Y,Gd)NbO4 phosphor was synthesized by solid-state reaction for possible application in cold cathode fluorescent lamps. A broad absorption band with peak maximum at 272 nm was observed which was due to the charge transfer between Eu3+ ions and neighboring oxygen anions. A deep red emission at the peak wavelength of 612 nm was observed which could be attributed to the 5D0→7F2 transition in Eu3+ ions. The highest luminance for Y1-x-yGdyNbO4:Eux3+ under 254 nm excitation was achieved at Eu3+ concentration of 18 mol.% (x=0.18) and Gd3+ concentration of 8.2 mol.% (y=0.082). The luminance of Y0.738Gd0.082NbO4:Eu3+0.18 was higher than that of a typical commercial phosphor Y2O3:Eu3+ and the CIE chromaticity coordinate was (0.6490, 0.3506), which was deeper than that of Y2O3:Eu3+. The particle size of the synthesized phosphors was controlled by the NaCl flux and particle size as high as 8 μm with uniform size distribution of particles was obtained.     

Infrared to near-infrared and visible upconversion photoluminescence of LiYbF4：Er3＋ nanorods

Colloidal LiYbF4:Er3+ nanorods were synthesized in an aqueous system which had the ratio of length to diameter of～2.These LiYbF4:Er3+ nanorods emitted intense upconversion light under excitation of infrared at 1488 nm.Importantly,the intensities of two-and three-photon anti-Stokes upconversion PL bands were observed which were comparable to that of the Stokes emission under excitation with low power density.The plots of excitation power density versus emission intensity indicated that all the emissions centered at 549,668,and 978 nm took a two-photon upconversion process.However,it could be simply deduced that the energy of two photons of 1488 nm were inadequate to produce a photon of 668 or 549 nm.For this conflict,the shape and saturation effects in the intermediate energy states were introduced to demonstrate the corresponding upconversion processes.     

Photoluminescence properties of nanosized strontium-yttrium borate phosphor Sr3Y2（BO3）4：Eu^3＋ obtained by the sol-gel Pechini method

Mixed strontium-yttrium borate phosphor Sr3Y2(BO3) 4 doped with Eu3+ ions was obtained by the sol-gel Pechini method.Crystal structure of the synthesized compound was analyzed by X-ray powder diffraction.Optimal conditions for the synthesis were found.Photo-physical properties of the phosphor samples were investigated by collecting excitation and luminescence spectra as well as measuring lumi-nescence lifetime.Judd-Ofelt analysis showed that Eu3+ ions occupied Y3+ sites in the crystalline network.The studied compound showed a red emission with the quantum yield of 54%-55% and can be potentially used as phosphor for plasma display panels and luminescent tubes.     

A novel green-yellow emitting phosphor Ca1.5Y1.5Al3.5S1.5O12：Ce^3＋ and its luminescence properties

We described the synthesis and luminescence of Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ phosphor for light emitting diode (LED). The crystal-linity, morphology, structure, and luminescence spectra were examined by X-ray diffraction, field emission-scanning electron microscopy and photoluminescence spectroscopy. The results showed that Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ phase was a dominating phase with little impurity phase peaks of Y2O3 when the sintered temperature reached to 1400 oC. Field emission scanning electron microscopy (FE-SEM) images showed the particle size of the phosphor was about 3 μm. Meanwhile, the excitation and emission spectra indicated that the as-prepared phosphors could be effectively excited by blue (460 nm) light and the excitation spectrum showed a broad band extending from 400-500 nm, while emission spectrum showed a broad yellow band peaking at 534 nm. The decay curve at the emission peak consisted of fast and slow components. The Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ should be a promising yellow phosphor for near blue-based white-light-emitting diodes (LEDs).     

Factors affecting afterglow properties of red-emitting phosphor MgSiO3：Mn^2＋,Nd^3＋ for luminescent fiber

With stable physical properties,the rare-earth silicate phosphor of MgSiO3:Mn2+,Nd3+ is one of the suitable luminescent materials used in preparing functional fibers.In order to promote the afterglow properties of red-emitting phosphors,we prepared it by means of solid-state reaction,and the effect of manufacturing elements including H3BO3 and environmental factor of calcining temperature,type of flux on its luminescence property were investigated through evaluating their afterglow properties.The results showed that with the concentration of Nd 3+ increasing,the amounts of H3BO3 doping and calcining temperature,the afterglow time and initial brightness of the rare-earth silicate phosphor increased and then decreased gradually.The afterglow properties of different flux concentration were different from one to another as:H3BO3 >Na+>K+>No flux.     

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.     

白光LED用LaPO4:Eu3+红色荧光粉的合成与表征

利用水热法制备了性能稳定的红色荧光粉LaPO4:Eu3+,同时研究了不同的Eu3+浓度、煅烧温度对荧光粉发光性能的影响.通过X射线粉末衍射(XRD)和扫描电子显微镜(SEM)来表征荧光粉的晶体结构和颗粒大小及形貌;用激发光谱和发射光谱以及荧光衰减曲线来表征荧光粉的荧光性能.结果表明:未煅烧时前躯体主要是六方晶相LaPO4·0.5H2O,煅烧温度在900℃时,所制备样品为单斜相LaPO4:Eu3+;SEM图像显示5 at.%Eu3+掺杂LaPO4呈椭球形,颗粒长约为500 nm,宽约为300 nm.最大发射波长和激发波长分别为592 nm和393 nm,发射光谱中592 nm和612 nm的发射峰对应的是Eu3+离子的5D0→7F1和5D0→7F2跃迁.其荧光寿命为3.32 ms.     

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.     

Dy3+ activated LaVO4 films synthesized by precursors with different solution concentrations

Using different-solution-concentration precursors with citric acid as chelating agent and polyvinyl alcohol as dispersing media, Dy3+ activated LaVO4 films were deposited on indium tin oxide (ITO) substrates. The scanning electronic microscope (SEM) showed that the compact and crack-free LaVO4:Dy3+ film could be obtained at a suitable solution concentration. The deposited films could absorb the ultra-violet light below 400 nm and were transparent in the visible and infrared region as evidenced by the transmission spectra, and the photolumines-cence spectra exhibited the characteristic emissions of Dy3+ peaking at 484 (blue) and 576 (yellow) nm due to the transitions of 4F9/2→6H15/2 and 4F9/2→6H13/2, respectively. The potential application of LaVO4:Dy3+ film in the dye-sensitized solar cell (DSSC) was also discussed.     

Synthesis and optical properties of Dy~（3＋）, Li~＋ doped CaMoO_4 phosphor

A series of CaMoO4 phosphors doped with trivalent dysprosium ions (Dy3+) and lithium (Li+) were prepared by solid state method at 750 °C for 3 h. X-ray diffraction (XRD) confirmed the crystal structure and quality of phosphors. Scanning electron microscopy (SEM) in- dicated that the phosphors presented good crystalline state, and the crystalline grain sizes were about 0.5-3.0 μm. The emission spectra showed that the phosphors had intense emission at 480 (4F9/2→6H15/2), 576 (4F9/2→6H13/2) and 660 nm (4F9/2→6...     

Effects of crystal field on photoluminescence properties of Ca2Al2SiO7:Eu2+ phosphors

A series of single-phased Ca₂Al₂SiO₇:Eu²⁺ phosphors were synthesized by the solid-state reaction. Their structure and photolumi-nescence properties were investigated by the X-ray powder diffraction （XRD） and excitation and emission spectra in detail. The emission spectra of Ca₂Al₂SiO₇:Eu²⁺ phosphors consisted of blue and green band located at419 and542 nm, respectively. The relative intensities of the blue and green emission changed with Eu²⁺ concentration and were sensitive to the excitation wavelength. The unique photoluminescence property originated from the 4f⁷→4f⁶5d transition of Eu²+ at different energy levels, on which the effect of the crystal field strength was con-sidered to be tailed by adjusting the host composition.     

Properties of red-emitting phosphors Sr2MgSi2O7:Eu3+ prepared by gel-combustion method assisted by microwave

Novel red-emitting phosphors Sr2MgSi2O7:Eu3+ were prepared by gel-combustion method assisted by microwave. The phase struc-ture and luminescent properties of as-synthesized phosphors were investigated by XRD and fluorescence spectrophotometer, respectively. The results showed that the as-synthesized sample was Sr2MgSi2O7 with tetragonal crystal structure. The excitation spectrum of Sr2MgSi2O7:Eu3+ was composed of two major parts: one was the broad band between 200 and 350 nm, which belonged to the charge transfer of Eu3+-O2-; the other consisted of a series of sharp lines between 350 and 450 nm, ascribed to the f-f transition of Eu3+. The emission spec-trum consisted of two emission peaks at 593 and 616 nm, which was attributed to 5D0→7F1 and 5D0→7F2 of Eu3+, respectively. The concen-tration of Eu3+ (x) had great effect on the emission intensity of Sr2-xMgSi2O7:Eu3+x. When x varied in the range of 0.04-0.18, the intensity of emission peaks at 593 and 616 nm increased gradually with the concentration of Eu3+ increasing. It was interesting that no concentration quenching occurred. Moreover, the luminescent intensity could be greatly enhanced with incorporation of charge compensator Li+ ions.     

Synthesis and luminescence properties of a novel red-emitting phosphor SrCaSiO_4：Eu~（3＋） for ultraviolet white light-emitting diodes

A novel red phosphor based on Eu3+-activated SrCaSiO4 was successfully synthesized by conventional solid state reaction method and the photoluminescence properties were investigated. X-ray diffraction (XRD) patterns indicated that SrCaSiO4:Eu3+ phosphors belong to orthorhombic crystal system (space group=Pmnb). The photoluminescence (PL) excitation spectrum showed broad-band absorption and the strongest excitation peak at 397 nm contributed to the 7F0→5L6 transition which matched well with the emission of a...