Co-Precipitation Preparation and Luminescent Behavior of (Y,Gd)BO3∶ Eu Phosphor

(Y,Gd)BO3∶ Eu phosphors were prepared by co-precipitation precursors, and luminescent properties were investigated. The precursors were synthesized by introducing hydroxyl ion to mixed solution of rare earth nitrates and boric acid, either through adding ammonia(precursor 1)or through controlled release of hydroxyl ion of urea(precursor 2). The precursors were fired in air at 1000 ℃ for 2 h. Resulted phosphor synthesized with precursor 1 has non-uniformed particle with mean diameter of about 3 μm, while that with precursor 2 exhibits uniformed near spherical-like morphology with mean diameter of about 300 nm. Phosphors with the two methods exhibit same crystal structure as that of commercial one. Emission spectra of the samples indicate that the sample prepared with precursor 2 shows relative higher intensity(exited by 172 nm VUV)than that prepared with the other precursor.     

Modification of Luminescent Properties of Red Sulphide Phosphors for White LED Lighting

A kind of sulphide, CaS:Eu2 , activated by europium ion for white LED lighting was synthesized via solid-state reaction route in reducing atmospheres. The phosphors were then encapsulated with silicone resin. Moreover, chemical structure of the phosphors was characterized by XRD. Microstructure of the powders was observed by SEM. Spectra of excitation and emission for the phosphors were also obtained by a spectrophotometer. Effect of processing parameters on the luminescent properties of the powders was systematically studied to result in the phosphors with good chemical stability and maximal relative luminescent intensity.     

Luminescence properties of Eu~(3+):NaGd(WO_4_)2 nanoparticles and nanorods

The NaGd(WO_4)_2:Eu~(3+) phosphors were prepared by the microemulsion mediated hydrothermal method. The morphology and size of the samples could be dependent on the p H in the initial solution. These phosphors obtained had a strong absorption at 395 nm matching with the popular emission of near-UV LED chips, and could emit intense red light at 616 nm. The small ellipsoid-like particles or short rods were provided with large parameters of oscillator strength ?_2 and asymmetry ratio. Compared to the ellipsoid-like phosphors, the rod-like phosphors took on stronger emission, longer lifetime and larger quantum efficiency. This work demonstrated that the one-dimension Na Gd(WO_4)_2:Eu~(3+) phosphors might be a more favorable device than zero-dimension ones for photoluminescence.     

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 ...     

X-ray-activated UVA long persistent luminescence from defective fluoride elpasolites

Long persistent phosphors have received significant attention owing to their attractive photophysical properties.Here,we report a new long persistent phosphor exhibiting strong ultraviolet A(UVA)afterglow.The phosphors were synthesized by a solid-state reaction method.We find that the obtained phosphors demonstrate super long UVA-afterglow emissions after irradiation by X-ray source,and the afterglow can last more than 50 h.A wide range of experimental characterizations indicate that the Tb~(3+)doped fluoride elpasolite phosphors are defective and some fluoride ions are replaced by oxygen ions,which creates electron traps with suitable trap depths.Our results establish that Tb3+can act as optical emitters in wide-bandgap hosts that can result in the UVA afterglow.This work enriches the bank of UV long persistent phosphors,and may stimulate more efforts for the design and synthesis of this kind of optical materials.     

Photoluminescent properties of Sr2SiO4:Eu3+ and Sr2SiO4:Eu2+ phosphors prepared by solid-state reaction method

Eu2+ and (or) Eu3+ doped Sr2SiO4 phosphors particles were synthesized by a conventional solid-state reaction technique, and their structural and optical properties were investigated. The X-ray diffraction (XRD) results showed that the obtained phosphors were composed of orthorhombic α'-Sr2SiO4 and monoclinic β-Sr2SiO4 phase. When excited under 256 nm, Sr2SiO4:Eu3+ phosphors showed intense emission in the red region. Sr2SiO4:Eu3+ phosphors exhibited white emissions (x=0.30, y=0.40, TC=6500 K) ranging from 425 to 650 nm when it was excited by near-ultraviolet (near-UV) light, indicating that Sr2SiO4:Eu2+ was a good light-conversion phosphor candidate for near-UV chip.     

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%.     

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。     

近紫外激发的荧光粉的获取方法和影响荧光粉发光性能的因素

利用近紫外LED芯片发出的近紫外光激发三基色荧光粉得到白光,其色温、显色指数等都由荧光粉的性能决定.本文对近紫外激发的荧光粉的获取方法和影响荧光粉发光性能的因素进行阐述,以便能够更好的研究和改善荧光粉的性能.     

Photoluminescence properties of M2ZnSi2O7:Eu2+（M=Sr,Ba）

The hardystonite phosphors of Eu2+ activated M2ZnSi2O7(M=Sr,Ba) were synthesized by combustion-assisted method.They were systematically characterized by photoluminescence excitation and emission spectra.The emission spectra of these two phosphors showed that the main emission peaks are at 475 and 503 nm due to 4f65d1→4f7 transition of Eu2+.Both phosphors could be efficiently excited in the wavelength range of 250-425 nm where the near ultraviolet light-emitting diode was well matched.The(x,y) color coordinates were determined with the emission values(x,y)=(0.41,0.21) and(0.16,0.45) for the M2ZnSi2O7:Eu2+(M=Sr,Ba) phosphors.     

Synthesis, characterization and luminescent properties of needle-like lanthanide-doped orthorhombic Y5O4F7

Thermal annealing of YOH1.1F1.9 and YOH1.1F1.9:Ln3+(Ln3+=Eu3+,Tb3+ and Gd3+) precursors in air gave access to synthesize yttrium oxyfluoride phosphors with well-preserved needle-like morphologies. The phase purities of samples strongly depended on the thermal annealing temperature. At 600 °C, pure Y5O4F7 with orthorhombic structure were obtained, as evidenced by powder X-ray diffraction measurement and chemical analysis. The interesting microstructure evolution of the annealed sample from well-organized nanoparticles on curly slices to microrod-bundle structure had been aroused by raising annealing temperature. The multicolor fluorescent emissions of Y5O4F7:Ln3+ phosphors were observed, e.g. ultraviolet emission for Gd3+ , green emission for Tb3+ and red emission for Eu3+ , which resulted from characteristic transitions of different lanthanide ions.     

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.     

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.     

助熔剂种类对绿色荧光粉（Ce0.67,Tb0.33）MgAl11O19晶体结构、形貌及发光强度的影响

采用高温固相法制备了三基色荧光灯用（Ce0.67,Tb0.33）MgAl11O19（CMAT）绿色荧光粉,研究了MgF2、AlF3、Li2CO3和H3BO34种助熔剂对CMAT绿粉物相纯度、粉体颗粒形貌和发光强度的影响。结果表明,用H3BO3做助熔剂制备的CMAT绿粉在物相纯度、粉体颗粒形貌和发光强度方面都优于其它三者。     

Luminescent properties of red phosphors K2Ba（MoO4）2：Eu3＋ for white light emitting diodes

K2Ba(MoO4)2:Eu3+ phosphors were synthesized by solid-state reaction. The emission and excitation spectra of K2 Ba(MoO4)2:Eu3+ phosphors exhibited that the phosphors could be effectively excited by near ultraviolet (394 nm) and blue (465 nm) light, and emitted red light at 616 nm. The influence of Eu3+concentration, sintering temperature and charge compensators (K+, Na+ or Li+ ) on the emission intensity were investigated. The results indicated that concentration quenching of Eu3+ was not observed within 30mol.% Eu 3+, 600 oC was a suitable sintering temperature for preparation of K2 Ba(MoO4)2:Eu3+phosphors, and K+ ions gave the best improvement to enhance the emission intensity. The CIE chromaticity coordinates of K2 Ba(MoO4)2:0.05Eu3+phosphor were calculated to be (0.68, 0.32), and color purity was 97.4%.     

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.     

YAG: Ce Phosphors for WLED via Nano-Pesudoboehmite Sol-Gel Route

The sub-micron sized YAG: Ce phosphors were synthesized via a modified sol-gel method by peptizing nano-pesudoboehmite particulate. It is found that YAG phase from the dried gel powders appears at 1000 ℃ then the pure YAG phase exists at a relatively lower sintering temperature of 1400 ℃. The smaller sizes of phosphors in the ranges of 1 ～ 3 μm are obtained due to the contribution of seeding effects of nano-sized alumina particles to strengthen each step of the processes. Both the excitation and emission spectra of photoluminescence of the phosphor obtained at 1400 ℃ meet well with the spectroscopic requirements of the WLED phosphors.     

Luminescence properties of YAl3(BO3)4 phosphors doped with Eu3+ ions

YAl3(BO3)4: Eu3+ phosphors were prepared by the conventional solid state reaction. The phase structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Doping YAl3(BO3)4: Eu3+ phosphors with concentration of Eu3+ ions of 0, 2, 5, 8 and 10 mol% were studied and their luminescent properties at room temperature were discussed. The excitation spectrum of Y0.95Eu0.05Al3(BO3)4 was composed of a broad band centered at about 252 nm and a group of lines in the longer wavelength re-gion. In the emission spectra, the peak wavelength was about 614 nm under a 252 nm UV excitation. The optimal doping concentration of Eu<3+ ions in YAl3(BO3)4: Eu3+ phosphors was 8 mol%.     

Preparation and Luminescence Properties of the New Long Phosphorescent Phosphors Ba1-xCaxAl2O4∶Eu2+,Dy3+

New long phosphorescent phosphors Ba1-xCaxAl2O4∶Eu2 , Dy3 with tunable color emission were prepared and studied. The emission spectra show that the tuning range of the color emission of the phosphors is between 498 and 440 nm, which is dependent on x, under the excitation of UV. The wavelength of the afterglow increases with the increasing of x until x equals 0.6. The XRD patterns show that the single phase limit in the phosphors is below x value of 0.4. The Thermoluminescence spectra were measured to investigate the traps created by the doping of Dy3 .     

Blue-Light Emission from Undoped and Rare Earth-Doped Wide Bandgap Oxides

Blue-light emitting materials have been receivingconsiderable attention due to their applications for avariety of optoelectronic devices and display technolo-gies . Rare earth-doped compounds have long founduses as blue phosphors in a variety of devices due totheir intensely luminescent f-d and f-f electronictransitions[1]. Metal sulfides ,such as ZnS have beenutilized as conventional phosphors due to their excel-lent brightness . However ,the life span of the displaydevices is li mited due t…