Judd-Ofelt parameters of the up-conversion phosphors: Er~(3+) doped BaGd_2ZnO_5/PMMA and NaYF_4/PMMA

We proposed a new approach to determination of Judd-Ofelt intensity parameters of Er~(3+) doped phosphors via their absorption spectra. To validate this approach, JO parameters of Er~(3+) doped Ba BaGd_2ZnO_5/PMMA and NaYF_4/PMMA composites were calculated and in a good agreement with the other glass and crystal. The spontaneous radiative transition probability, branching ratio, and radiative lifetime of the optical transitions were calculated by using the Judd-Ofelt theory. Intense near-infrared emission at 1553 nm was observed under 980 nm laser diode excitation at room temperature. The samples possessing high full-width at half-maximum reach 85 nm have potential application in broadband optical amplifier.     

Effect of mixing process on the luminescent properties of SrAl_2O_4:Eu~(2+),Dy~(3+) long afterglow phosphors

A new mixing method was developed for solid-state reaction synthesis of SrAl2O4:Eu2+,Dy3+ long afterglow phosphors.The morphology and crystal structure of the phosphors were analyzed with scanning electron microscope(SEM) and X-ray diffractometer(XRD).The excitation and emission spectra of the long afterglow phosphors were measured,and the main emission band was around 514 nm.The decay time of the product was measured and compared with the phosphors prepared using dry-mixing method and wet-mixing method.It ...     

蓝色荧光粉NaBa0.98PO4:Eu2+0.02的制备和发光性能研究

采用高温固相反应法合成了蓝色荧光粉NaBa0.98P04:Eu2+0.02.利用射线衍射(XRD)、扫描电镜(SEM)和荧光光谱等实验技术,研究了掺杂离子和掺杂浓度对荧光粉的晶体结构和发光性能的影响.结果表明:制备的粉末为单斜晶系NaBaP04,能被从紫外到蓝光波长范围的激发光有效激发,在波长360nm激发光激发下,发射光为波长在430nm左右的蓝光.同时,研究表明最佳掺杂离子为Ca2+,最佳掺杂浓度为7％ mol,荧光粉NaBa0.91Ca0.07PO4:Eu2+0.02的发光强度是NaBa0.98PO4:Eu2+0.02的1.68倍,该方法制备的荧光粉是一种很好的白光LED的蓝色荧光粉材料.     

Synthesis of Long Afterglow Phosphors MAl2O4:Eu2+, Dy3+(M=Ca, Sr, Ba) by Microemulsion Method and Their Luminescent Properties

Long afterglow phosphors MAl2O4:Eu2 , Dy3 (M=Ca, Sr, Ba) were synthesized by microemulsion method, and their crystal structure and luminescent properties were compared and investigated. XRD patterns of samples indicate that phosphors CaAl2O4:Eu2 , Dy3 and SrAl2O4:Eu2 , Dy3 are with monoclinic crystal structure and phosphor BaAl2O4:Eu2 , Dy3 is with hexagonal crystal structure. The wide range of excitation spectrum of phosphors MAl2O4:Eu2 , Dy3 (M=Ca,Sr,Ba) indicates that the luminescent materials can be excited by light from ultraviolet ray to visible light and the maximum emission wavelength of phosphors MAl2O4:Eu2 , Dy3 (M=Ca, Sr, Ba) is found mainly at λem of 440 nm (M=Ca), 520 nm (M=Sr) and 496 nm (M=Ba) respectively, the corresponding colors of emission light are blue, green and cyna-green respectively. The afterglow decay tendency of phosphors can be summarized as three processes: initial rapid decay, intermediate transitional decay and very long slow decay. Afterglow decay curves coincide with formula I=At-n, and the sequence of afterglow intensity and time is Sr＞Ca＞Ba.     

Luminescence properties and energy transfer of host sensitized CaMoO4：Tb^3＋ green phosphors

A series of CaMoO 4 :xTb 3+(x=0.01,0.03,0.05,0.07,0.09,0.15 and 0.20) phosphors in pure phase were prepared via high temperature solid-state reaction approach.The crystal structure of the phosphors was investigated by X-ray diffraction(XRD),and the optical properties were investigated by Fourier transform infrared spectroscopy(FT-IR),ultraviolet-visible spectroscopy(UV-Vis) and photoluminescence(PL) spectroscopy.The PL spectra illustrated that these phosphors could be efficiently excited by the charge transfer band of the host and the energy transfer efficiency from the host to the doped activator reached 60% when the doping concentration of the activator Tb 3+ was 20 mol.%.The concentration quenching occurred at x=10 mol.%,from which the critical distance of activator was calculated to be about 1.14 nm.The CIE coordinates were estimated to be close to the standard green value.The host sensitized samples had potential application as green phosphors.     

Effect of red emitting fluorescent pigment on fluorescent color of SrAl_2O_4:Eu~(2+),Dy~(3+) phosphors

Green-blue fluorescence emitting SrAl_2O_4:Eu~(2+),Dy~(3+) phosphors(SAOED) were coated by SiO_2 and a coumarin type red-emitting fluorescent pigment(FP).The effects of the FP on the morphology,crystal structure,photoluminescence properties and fluorescent color of the SAOED phosphors were systematically investigated by scanning electron microscopy(SEM),FT-IR,X-ray diffraction(XRD),photoluminescence spectra and CIE-1931 chromaticity coordinates characterization.Even though the surface of the SAOED phosphors became rough after being coated with SiO_2 and FP,crystal lattice of SrAl_2O_4 did not have any obvious lattice distortions.The photoluminescence spectra indicated that the SAOED phosphors could be used as the excitation light source to excite the FP to emit red fluorescence.The emission spectrum of the FP-coated SAOED consisted of a broad band with two emission peaks at 520 and 610 nm,and its fluorescence emission color was a mixed color of the SAOED phosphors and FP.The fluorescence color of the SAOED/SiO_2/FP composites tended to transfer to red area with the increase of the FP content varying from 0.1%to 0.9%.     

Eu3+激活的Li2Gd4（MoO4）7钼酸盐红色荧光体及其发光性质

由高温固相反应首次合成Li2(Gd1-xEux)4(MoO4)7(0相似文献   

PMMA with Long-Persistent Phosphors and Its Behavior of Luminescence

A new kind of rare earth material with high efficient long-persistent phosphors, such as SrAl2O4:Eu, Dy, has been developed in recent years. The PMMA with long-persistent phosphors is typical one of applications for the phosphors. In this work, we try to probe into the affection of the manufacture process on the PMMA with long-persistent phosphors, to analyze its performance, and its luminescence behavior, especially to study the self-excitation of the PMMA with long-persistent phosphors.     

Study on co-precipitation synthesized Y3Al5O12:Ce yellow phosphor for white LED

A precursor of the Y3Al5O12:Ce (YAG:Ce) phosphor was obtained by co-precipitation of the solution of high purity nitrates with ammonium bicarbonate solution. The precipitation process of the precursor was studied in this work. YAG:Ce yellow phosphors with fine morphology was synthesized by annealing the precursor at a reducing atmosphere. The crystal phase, microstructure of the phosphors and their photoluminescence were investigated. The results indicated that the pure phase of YAG:Ce could be obtained at ...     

SrS:Ce3+,K+荧光体的微波辐射合成法及对发光特性的影响

本文首次用微波辐射法（ＭｉｃｒｏｗａｖｅＲａｄｉａｔｉｏｎＭｅｔｈｏｄ，简称ＭＲＭ）合成了纯的ＳｒＳ基质和ＳｒＳ∶Ｃｅ３＋，Ｋ＋蓝色荧光化合物，用ＸＲＤ测定了它们的晶体结构，系统考察了不同浓度的Ｃｅ３＋离子对发光性能的影响。实验发现，微波辐射能使Ｃｅ３＋在ＳｒＳ基质晶格中均匀扩散，并能提高激活剂的掺入量，阻止Ｃｅ３＋离子的簇集，延缓Ｃｅ３＋离子对的形成，从而能得到晶相纯、粒度均匀和发光效率高的ＳｒＳ∶Ｃｅ３＋，Ｋ＋蓝色荧光体。     

Rare earth double activated phosphors for different applications

For the purpose of development of highly energy-efficient light sources,one needs to design highly efficient green,red and yellow phosphors,which are able to absorb excitation energy and generate emissions.In this contribution,we present our results on producing some efficient phosphors with improved luminescence properties.Using double activation,energy could be transferred from one luminescent activator to the other one,resulting in more efficient or brighter device operation.Co-activators could be added to a host material to change the color of the emitted light.The incorporation of Eu3+ or Tb3+ ions into the CaWO4 crystal lattice modified the luminescence spectrum due to the formation of the emission centers that generated the specific red and green light.Very efficient new red phosphors based on YNbO4 and doped by Eu3+,Ga3+,Al3+ allowed recommending these materials as good candidates for different applications including LED and X-ray intensifying screens.For double activated TAG with Ce3+ and Eu3+ and for different mole ratios of Ce/Eu,the color temperature changed from 5500 K(0.331,0.322) up to 4200 K(0.370,0.381) and the light became "warmer".Application of TAG:Ce,Eu in the light emitting device showed better chromaticity coordinates of luminescence and color rendering index of LEDs.     

(Zn, Ca) Solid-Solution Behavior and Its Effect on Luminescence Properties in Ca1- xZnx TiO3: 0.002Pr3+ Phosphors

Nominal composition of Ca1 - xZnxTiO3: 0. 002Pr3 ( x = 0. 000 ～ 0. 200) phosphors were prepared by conventional solid reaction route. XRD and PL measurements were used to investigate the solid-solution structure and luminescence properties of Zn-doped Ca1- xZnxTiO3:0. 002Pr3 phosphors. The effect of solid-solution structure formed by substitution between Ca2 and Zn2 ions on the luminescent properties was analyzed. The results reveal that, with the increase of Zn substitution content below 0.010, lattice parameters and the intensity of excitation peak at both 260 and 330 nm as well as the corresponding 610 nm emission intensity are monotonously decreased quickly in a similar tendency. Also, the evolution of luminescence intensity and crystal cell parameters against Zn doping concentration are in good agreement.Above results are closely related with the structure change within Ca1- xZnxTiO3:0. 002Pr3 solid-solution phase formed by the Zn ions substitution for the Ca sites. Present study reveals that the solid-solution structure formed by substitution between Ca2 and Zn2 ions has significant effect on the luminescence properties of single phase Ca1- xZnxTiO3:0.002Pr3 phosphors.     

Photoluminescence characterization and energy transfer of NaBa1-x-yPO4：xCe3＋, yTb3＋ phosphors

A series of NaBa1-x-yPO4: xCe3+, yTb3+ phosphors were synthesized by solid-state reaction method. The crystal structure, photoluminescence emission and excitation spectra and decay times of the phosphors were carefully investigated. The results revealed that an efficient energy transfer occurred from Ce3+ to Tb3+ ions in NaBaPO4 host by means of dipole-dipole interactions and the critical distance of the energy transfer was about 0.638 nm. Moreover, the phosphor emitted strong green emission under UV excitation, indicating that the phosphors are potentially useful as a highly efficient, green-emitting phosphor.     

Effect of detrapping on up-conversion charging in LaMgGa11O19:Pr3+ persistent phosphor

Up-conversion charging (UCC) is a promising approach for charging storage phosphors using low-energy excitation light sources. For further understanding the UCC, research on the competition between trapping and detrapping during illumination is essentially required. Here we demonstrate the effect of detrapping on UCC dynamics by a rate equation approach. Accordingly, taking LaMgGa₁₁O₁₉:Pr³⁺ phosphor as an example, we experimentally verified the dependence of illumination dose and duration on the thermoluminescence intensities using 450 nm laser excitation. The present model and experimental approach appear to be transferable to other phosphors. Thus, many existing persistent phosphors can now be revisited, paving the way toward advancing the understanding of UCC.     

Color tunable and white light emitting via energy transfer in single-phase BiOCl:Er3+,Sm3+ phosphors for WLEDs

BiOCl crystal shows potential as efficient optical host due to its special layered structure. Here,the luminescence properties of the Er~(3+)/Sm~(3+) co-doped BiOCl phosphors as single-phase phosphors were reported. Upon near ultraviolet excitation(NUV, 380 nm corresponding the ~4 I_(15/2)→ ~4 G_(11/2) transition of Er~(3+) ions), the phosphors exhibit the efficient characteristic emissions of Er~(3+) and Sm~(3+) ions simultaneously. The energy transfer(ET) from Er~(3+) to Sm~(3+) ions in the layered crystals has been validated by the variation of emission intensities and decay lifetimes respectively, which is ascribed to be a dipoledipole interaction. By virtue of the ET behavior and increasing Sm~(3+) ion concentration, the enhancing emission intensity of Sm~(3+) and the tunability of emission color from yellowish-green(0.318, 0.420) to white(0.343, 0.347) are realized. The results of our work indicate that the Er~(3+)/Sm~(3+) co-doped BiOCI phosphor has a promising application serving as single component white emitting phosphors for NUV excited WLEDs.     

Long-Lasting Properties of Rare Earth-Doped Y2O2S Phosphors

The aim of this presentation is to report a new result of afterglow materials. The Y2O2S:Ln^3 (Ln = Sm, Tm)phosphors show bright reddish orange and orange-yellow colors when excited by UV or visible light. The main spectroscopic characterizations of Sm^3 and Tm^3 in yttrium oxysulfide and their long-lasting phosphorescence were measured and discussed in this presentation. Their long-lasting phosphorescence can be seen by the naked eyes clearly for about one hour in the dark room after the irradiation light sources were removed. XRD and photoluminescence (PL) spectra as well as the luminance decay were used to characterize these long-lasting phosphorescence phosphors. The results of XRD indicate that the products synthesized through the flux fusion method under 1050℃ for 6 h have a good crystallization without any detectable amount of impurity phase. Both the PL spectra and luminance decay results reveal that these phosphors have efficient luminescent and good long-lasting properties. We believe that the experimental data gathered in our present work will be useful in finding some new long-lasting phosphors with different colors.     

New red phosphor （Y, Gd, Lu）BO3： Eu^3＋ for PDP applications

Highly efficient phosphors under vacuum ultraviolet excitation are still demanded for the development of plasma display panels and Hg-free fluorescent lamps. The phosphors of Eu3+ doped (Y, Gd, Lu)BO3 were synthesized with solid state reaction method and the con-tents of Y3+, Gd3+, and Lu3+ for plasma display panel red phosphor were optimized under vacuum ultraviolet excitation. Two new potential candidates, which were (Y1-S-7TGdSLuT)BO3: Eu3+ (0相似文献   

A novel blue-purple Ce~(3+) doped whitlockite phosphor:Synthesis,crystal structure,and photoluminescence properties

At present,the rare earth(RE) ions doped phosphors have attracted more and more attention because of their excellent properties.In this paper,a series of novel blue-purple β-Ca_3(PO_4)_2:Ce~(3+) phosphors were synthesized by a high temperature solid phase method.The X-ray diffraction(XRD),infrared spectrum,energy dispersive spectroscopy(EDS),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),photoluminescence excitation and emission spectra were used to investigate the crystal structure,composition and the luminescent properties of the resulting samples.The phosphor shows a strong absorption in the ultraviolet band.Under the excitation of 269 nm,the phosphor emits a strong purple fluorescence ranging from 360 to 520 nm.When Ce~(3+) doping content is 0.07 mol,the strongest luminescence intensity is reached,and the concentration quenching mechanism is dipole-dipole(d-d)interaction for Ce~(3+) based on Dexter theory.     

A novel long lasting phosphor Sr5 （PO4）3FxCll_x：Eu2＋,Gd3＋ prepared in air condition

A series of blue long afterglow mixed halide-phosphate phosphors Sr5 （PO4）3 FxCll-x：Eu2＋,Gd3＋ were synthesized in air by traditional solid-state reaction routte. The crystal structures, photoluminescence, thermolurninescenee properties and afterglow proper- ties of the phosphors were characterized systematically using X-ray diffraction （XRD）, luminescence spectrophotometer, microcom- puter thermoluminescence dosimeter and single photon counter, respectively. Under 280 nm excitation, the broadband emissions of Eu2＋ ions were observed at 445 nm （blue） due to the 4f7→4f65d transition. It was demonstrated that there existed the self-reduction of the Eu3＋ to Eu2＋ ions in this special halide-phosphate matrix in air condition. The addition of Gd3＋ ions obviously enhanced the after- glow properties of the single doped Eu2＋ ions in the halide-phosphate phosphors. And the content of the fluoride anions also had sig- nificant influence on the afterglow properties. All results indicated that Srs （PO4）3 FxCI1-x：Eu2＋,Gd3＋ might be potential phosphors for long lasting phosphorescence （LLP） materials.     

High temperature stability of Eu2＋-activated nitride red phosphors

The novel nitride-based luminescent materials have received much attention since the end of the last century. In this paper, the commercial Eu2＋-activated nitride red phosphors, Sr1.95Si5N8：Eu0.05, Sr1.85Si5N8：Eu0.15 and Ca0.99AlSiN3：Eu0.01 phosphors were an-nealed at different temperatures （beyond 300 oC） to investigate the dependence of their luminescence performance and structure vari-ability on the temperature. By photoluminescence spectra, X-ray diffraction （XRD） and thermogravimetry-differential scanning calo-rimetry （TG-DSC） analysis, the high temperature stability of the hosts and activator of the three samples were disclosed. With the an-nealing temperature increasing, the activator Eu2＋ions were firstly oxidized and then host in Sr1.95Si5N8：Eu0.05 and Sr1.85Si5N8：Eu0.15, but for Ca0.99AlSiN3：Eu0.01, only the oxidation of the host could be observed, which would lead to the luminescence degradation and even failure of these phosphors. The activator Eu2＋ions were much more stable in CaAlSiN3：Eu than Sr2Si5N8：Eu due to their crystal surroundings, and its concentration also influenced the temperature stability of Sr2Si5N8：Eu.