Luminescent properties of Dy~(3+)/Eu~(3+) doped fluorescent glass for white LED based on oxyfluoride matrix

Rare earth ion-doped fluorescent glass has become a hotspot due to its characteristics.This work shows that the prepared Dy~(3+)and Dy~(3+)/Eu~(3+)doped glasses have white light emission under ultraviolet excitation.There is a higher yellow light/blue light(Y/B) value,indicating an increase in the covalentity of Dy-O,and decrease in the symmetry with the increasing concentration of dopants(Dy~(3+)).The correlated color temperature(CCT) can be effectively reduced by the red light emission of Eu~(3+),and the order of influence of excitation wavelength on CCT is 395 nm 382 nm 365 nm.The delay curve demonstrates the energy transfer from Dy~(3+)to Eu~(3+).The glass has the characteristics of anti-blue light damage and wide tunable color temperature,which illustrates that it has potential application in the field of white LED.     

Optical performance study of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) ternary luminous fiber

In this study, down-conversion fluorescent powder of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+), which were the common three primary colors materials with long afterglow, were synthesized by high temperature solid state method. The blends of rare earth(RE) luminescent materials have been of interest to reinvest the luminescent characteristics of polyethylene terephtahalate(PET) luminous fiber. The scanning electron microscopy(SEM) and an inversion fluorescence microscope were used to characterize the surface morphology and the dispersion of inclusion. Through analysis of microcosmic morphology, three typical dispersions of luminescent particles were summarized. The X-ray diffraction indicated that the phase structure of fiber samples and crystal structure of luminescence materials kept complete after prilling and spinning. From the fluorescence spectra and CIE 1931 coordinates, it could be found that different combinations of luminous fibers were desired to obtain divers colors emission luminous fiber. And the fiber samples were a light sensation which could induct different excitation wavelengths and convert it down to different colors. The afterglow decay curve and its differential curve were summarized indicating the three decay stages. The decay curve and decay rate curve showed that the contents of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) had obvious influence on the afterglow of fiber samples.     

Luminescence characteristics of Dy~(3+) doped Gd_2O_3-CaO-SiO_2-B_2O_3 scintillating glasses

Glasses were prepared from the compositions of 25Gd_2O_3-10 CaO-10 SiO_2-(55–x)B_2O_3-xDy_2O_3(where x is 0.0 mol.%–1.0 mol.%) by the conventional melt-quenching technique at 1400 oC. The results demonstrated the increase in the glass density with respect to the increase in the doping concentrations of Dy_2O_3. Nine absorption bands were observed. The emission spectra of the developed glass showed two strong peaks at 577 nm(~4F_(9/2)→~6H_(13/2)) and 482 nm(~4F_(9/2)→~6H_(15/2)). The highest emission intensity was observed from the developed glass prepared at 0.4 mol.% of Dy_2O_3, as the efficient energy transfer took place from Gd~(3+) to Dy~(3+). From the X-ray induced optical luminescence, the emission spectra were identical to those from PL measurements, but with the highest intensity observed from the glass quenched at 0.45 mol.% of Dy_2O_3. Finally, the integral scintillation efficiency of the developed glass was determined at 27% of that of the commercially available BGO crystal.     

SrAl_2O_4:Eu~(2+),Dy~(3+)的发光性质及机理

研究了Eu2＋、Dy3＋共激活的SrAl2O4体系的发光性能和能量传输。结果表明，Dy3＋、Eu2＋共存时，Eu2＋的发光强度远远大于无Dy3＋时的发光强度，证明Dy3＋对Eu2＋的发光有敏化作用。Dy→Eu2＋能量传输的方式为籍助于载流子的能量输运。     

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+.     

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 ...     

Influence of annealing temperature on luminescent properties of Eu~(3+)/V~(5+) co-doped nanocrystalline Gd_2Ti_2O_7 powders

Nanosized Gd2(1-x)Eu2xTi2O7:yV5+ phosphors were prepared via sol-gel method and characterized with X-ray diffraction,Raman spectroscopy,diffuse reflectance spectra and photoluminescence spectra.Their PL properties were investigated as functions of the Eu3+ doping concentration and annealing temperature.The results indicated that the as-prepared samples showed a strong emission of Eu3+ under the irradiation of 303 nm.For Eu3+-doped Gd2Ti2O7,the orange emission at 586 nm was the strongest,which was correspond...     

Preparation and luminescence properties of rare-earth doped fiber with spectral blue-shift: SrAl_2O_4:Eu~(2+),Dy~(3+) phosphors/triarylsulfonium hexafluoroantimonate based on polypropylene substrate

The rare-earth doped fiber with spectral blue-shift based on long afterglow luminescent materials SrAl_2O_4:Eu~(2+),Dy~(3+) phosphors and an organic cationic photoinitiators-triarylsulfonium hexafluoroantimonate(TSHF) in the presence of polypropylene substrate(PP) was prepared by melt-spinning process. Scanning electron microscopy(SEM), infrared spectroscopy(IR), afterglow properties and luminescence properties were tested. The results of SEM and FTIR spectra showed that the fiber consisted of irregular particles and had independent structural constitution of SrAl_2O_4:Eu~(2+),Dy~(3+) phosphors, TSHF and polypropylene. Furthermore, it was observed that there existed the highest afterglow initial intensity for the fiber with the TSHF concentration of 5 wt.%. More interestingly, the emission peak shifted to blue area gradually as the TSHF doping increased. The rare-earth doped fiber was distributed on blue light area in the CIE 1931 chromaticity diagram, which showed more obvious blue-shift phenomenon than the yellow-green light of SrAl_2O_4:Eu~(2+),Dy~(3+) phosphors.     

Effect of light conversion agent on luminous properties of a new down-converting material SrAl_2O_4:Eu~(2+),Dy~(3+)/light conversion agent

A new luminous material SrAl_2O_4:Eu~(2+),Dy~(3+)/light conversion agent that can emit red light in the darkness after being excited was fabricated by combining light conversion agent on to SrAl_2O_4:Eu~(2+),Dy~(3+) particles through YsiX3.The morphology of the luminous materials was analyzed by scan electron microscopy(SEM).The emission behavior was evaluated by fluorescence spectrophotometric analysis and the results demonstrated that the emission spectra of samples had a redshift compared to SrAl_2O_4:Eu~(2+),Dy~(3+) and the emission intensity rose dramatically at first and then decreased when the ratio of light conversion agent doping was over 1.4 wt.%.And the emission color of SrAl_2O_4:Eu~(2+),Dy~(3+)/light conversion agent was tuned from green(SrAl_2O_4:Eu~(2+),Dy~(3+))to orange-red.Furthermore,the afterglow property was also investigated,and the results indicated that the afterglow brightness reached 6.5 cd/m~2,and as the light conversion agent concentration increased the brightness intensity decreased.     

Luminescence properties of Eu~(3+) doped YBO_3 for temperature sensing

YBO_3:2 at.% Eu~(3+) was prepared by the solid state reaction and its temperature dependent luminescence was investigated for possible applications in temperature sensing. Phase composition of this material was confirmed by X-ray powder diffraction analysis and excitation and emission spectra were also provided. Under excitation of 355 nm, the fluorescence originating from ~5D_0 and ~5D_1 states varied as the temperature rose in a region from 333 to 773 K. The fluorescence intensity ratio(FIR) of ~5D_0 and ~5D_1 was investigated which increased significantly with the rise of temperature. The maximal relative sensitivity in the whole temperature range was 1.8% K~(–1)(at 333 K). The results recommended YBO_3:Eu~(3+) as a new material of the FIR method for non-contact optical thermometry.     

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%.     

Synthesis and characterization of monodisperse Eu~(3+) doped gadolinium oxysulfide nanocrystals

Gd_2O_2S:Eu~(3+) nanoparticles were synthesized using two step process consisting of sulfuration of basic carbonates obtained by homogenous precipitation.Annealing of lanthanide nitrates at total concentration of 5×10~(-3) mol/L in a water solution containing relatively high,three molar concentration of urea ensured the optimal conditions for the reproducible preparation of uniform and small spherical particles.During sulfuration step elemental sulfur was mixed with precursor which eliminated necessity of using an auxiliary furnace and provided sulfur-reach reaction atmosphere.Such optimized protocol afforded synthesis of spherical and non-agglomerated nanoparticles with diameter smaller than 100 nm.The precursors morphology was maintained,but particles size was reduced by 15%-20%during sulfuration.The results indicated that higher emission intensity was observed for Gd_2O_2S:Eu~(3+)(8%)oxysulfide sample synthesized using crystalline Gd(CO_3)OH precursor,than for that obtained from amorphous Gd_2(OH)_2(CO_3)_2·H_2O precursor,although some further efforts to improve morphology of the former are still required.     

Optically stimulated luminescence of Dy~(3+)-doped NaCaPO_4 glass-ceramics

Dy~(3+)-doped glass-ceramics containing NaCaPO_4 crystals were successfully fabricated by heat treatment at base glass,and the luminescence properties were investigated for potential applications in radiation measurements.The photo luminescence(PL) excitation and emission spectra exhibit transitions related to Dy~(3+) ions corresponding to the strongest excitation and emission wavelengths at 351 and 575 nm,respectively.The CW-OSL properties as a function of dopant concentration,pre-heating temperature,pre-heating time and signal fading were investigated.The most appropriate Dy~(3+)ion concentration was found to be 0.25 mol%.The TL glow curves have a broad peak feature peaking at 195±5 ℃.The fading of the OSL signal would keep stable in five days with the intensity value of about 76.11%.The samples also exhibit good signal reusability and a broad linear dose response range(0.02-1000 Gy).     

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...     

Luminescence of Eu~(2+) and Eu~(2+)-Mn~(2+) in sodium scandium diphosphate NaScP_2O_7 crystal

In this work, the photoluminescence(PL) of NaScP_2O_7:Eu~(2+) and NaScP_2O_7:Eu~(2+),Mn~(2+) was investigated. Phase purity was checked using X-ray powder diffractometry(XRD). PL excitation and emission spectra were recorded to elucidate the PL properties of NaScP_2O_7:Eu~(2+) and NaScP_2O_7:Eu~(2+),Mn~(2+). Furthermore, fluorescence lifetime measurements were performed. PL and lifetime measurements were carried out from 10 to 525 K. Moreover, the Eu~(2+) site occupation was discussed. It turned out that the incorporated Eu~(2+) ions substituted for Na+ site and occupied two different sites. Temperature dependent PL measurements indicated the emission intensity decreased with increasing temperature due to temperature quenching in NaScP_2O_7:Eu~(2+). Fluorescence lifetimes of Eu~(2+) in NaScP_2O_7:Eu~(2+) almost did not change with a decay constant τ=~0.53 μs in the temperature range of 10–280 K, and then shortened due to temperature quenching. The luminescent lifetime reached ~0.05 μs at T=525 K. Finally, it was found that energy transfer occurred from Eu~(2+) to Mn~(2+) in co-doped NaScP_2O_7:Eu~(2+),Mn~(2+).     

复合熔盐法合成Y2O3.Eu3+红色荧光粉

以草酸钇铕(Y2(C2O4)3:Eu3+)为前驱体,采用复合熔盐(NaCl+S+Na2CO3)协助焙烧法合成Y2O3:E.u3+红色荧光粉.利用XRD、SEM、光谱分析等测试和分析荧光粉粒径、颗粒形貌以及发光性能.主要考察复合熔盐配比、用量以及焙烧温度和时间对Y2O3:Eu3+荧光粉发光性能的影响.结果表明,NaCl在...     

Synthesis and optical properties of Eu~(3+) ion doped nanocrystalline hydroxya patites embedded in PMMA matrix

Transparent,luminescent and functional nanocomposites demonstrate interesting optical and mechanical properties suitable for many optoelectronic applications.Transparent polymethyl methacrylate(PMMA) polymer nanocomposites modified with thenoyl-trifluoroacetonate(TAA) were fabricated by in situ polymerization and used as hosts for homogenous dispersion of 3 mol.% Eu3+:Ca10(PO4) 6(OH) 2(Eu3+:HA) hydroxyapatite ～20 nm large nanocrystals.The emission,excitation and transmission spectra as well as the fluorescence decay rates of bare Eu3+:HA nanocrystallites,Eu3+:HA embedded in the PMMA and and Eu:HA embedded in the PMMA/TTA nanocomposites were studied.The improvement of transparency was demonstrated with the addition of TTA as well as europium doped hy-droxyapatites in comparison to pure PMMA matrix.The Judd-Ofelt analysis of f-f transitions of Eu3+:HA nanocrystallites,the PMMA/Eu3+:HA and the PMMA+TTA/Eu3+:HA was performed to investigate the optical behavior of the polymeric composites.     

Phase separation and crystallization of La_2O_3 doped ZnO-B_2O_3-SiO_2 glass

In order to investigate the effect of the La_2O_3 on the phase separation and crystallization of ZnO-B_2O_3-SiO_2 glass, after the occurence of the phase separation and crystallization of glasses by heat treatment, the microstructure morphology and distribution of elements in different sample areas were characterized by the scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS); the non-isothermal crystallization kinetics of the glass samples was studied by using a differential scanning calorimeter(DSC) and the precipitated crystals of crystallized glass were determined by the X-ray diffraction(XRD). The results suggest that the phase separation and crystallization of 60ZnO-30 B_2O_3-10SiO_2 glass occur at glass surface, and the incorporation of small amount(4 mol%) of La_2O_3 significantly inhibits the glass phase separation and consequently improves the thermal stability of glass.Doping of La_2O_3 accelerates the glass crystallization at the elevated temperature(660 ℃), making the depth of crystal layer thicker and diffraction intensity in XRD patterns stronger. However, due to the precipitation of several crystals that occur simultaneously when La_2O_3 doping amount is 4 mol%, crystallization of the 60ZnO-30B_2O_3-10SiO_2 glass is obviously depressed, the crystallization activation energy Ec and the relative crystallinity X_c of the glass reach the maximum and the minimum values, respectively.Although transition from one-dimensional growth of crystals to two-dimensional growth of crystals results from La_2O_3 addition, the one-dimensional growth of crystals remains dominant in crystallization process. This work can provide some useful information for preparing glass ceramics with nano-crystals precipitated in the glass surface.     

Structural characterization and temperature-dependent luminescence of CaF_2:Tb~(3+)/Eu~(3+) glass ceramics

Tb~(3+)/Eu~(3+) co-doped transparent glass ceramics containing CaF_2 nanocrystals were successfully synthesized by high temperature melt-quenching method and subsequent heating. The structure and morphology of the samples were investigated by X-ray diffraction(XRD), transmittance electron microscopy(TEM), high resolution TEM(HRTEM) and selected area electron diffraction(SAED). The photoluminescence properties and energy transfer process from Tb~(3+) to Eu~(3+) of CaF_2:Tb~(3+),Eu~(3+) phosphors were also investigated through excitation spectra and decay curves. In addition, the emission spectra of the glass ceramics in a wide temperature range from 21 to 320 K were recorded under the excitation of 485 nm. It was found that the fluorescence intensity ratios of Tb~(3+) at 545 nm(~5D_4→~7F_5) to Eu~(3+) at 615 nm(~5D_0→~7F_2) was highly temperature-dependent with an approximate linear relationship, and the temperature sensitivity was about 0.4%/K. It is expected that the investigated Tb~(3+)/Eu~(3+) co-doped CaF_2 glass ceramics may have prospective application in optical thermometry.     

Photoluminescence properties of Eu~(3+)-doped MgAl_2O_4 nanoparticles in various surrounding media

Eu~(3+)-doped MgAl_2O_4 nanoparticles were prepared by modified Pechini method.X-ray diffraction analysis shows pure tetragonal spinel phase without any impurities.The average size of synthesized nanoparticles was determined to be about 50-60 nm using scanning electron microscopy and static light scattering techniques.Emission and excitation spectra as well as lifetimes of MgAl_2O_4:Eu~(3+) nanophosphors were explored in surrounding media with different refractive indexes.Surrounding medium does not affect luminescence bands position,whereas ~5D_0 lifetime monotonically decreases along with increase of medium refractive index.Effect of surrounding media on radiative and nonradiative decay rates,which were calculated using 4f-4f intensity theory,was studied and discussed.Filling factor of prepared nanoparticles is defined using both radiative and observed lifetimes.