Re-determination of the crystal structure of Ca₂Y₈Si₆O₂₆ and study on the luminescent properties of Ca₂Y₈Si₆O₂₆:Tb³⁺

The crystal structure of silicate oxyapatite Ca2Y8Si6O26 was indexed as hexagonal,space group P63/m,a=0.93515 nm,c=0.67872 nm,α=β=90°,γ=120°,V=0.5138692 nm3.Three strong peaks located at 32.079o,32.595o,and 50.104o with d=2.7903,2.74649,1.8194 was in accordance with,(112),and(213) planes.The optimum concentration of Tb3+ in Ca2Y8Si6O26 to yield highest photoluminescence intensity was 10 mol.% of Y3+.The corresponding excitation spectrum consisted of an intense broad band from 220 to 260 nm.The photoluminescence measurements showed that the green emission originated from 5D4-7F5 was predominant in the measured range with strong doublet lines at 543 and 549 nm.     

Photoluminescence study of SiO₂ coated Eu³⁺:Y₂O₃ core-shells under high pressure

Uniform core-shell Eu3+:Y2O3/SiO2 spheres were synthesized via precipitation and the Stber method.The structural transition of core-shell Eu3+:Y2O3/SiO2 was studied by using high pressure photoluminescence spectra.With pressure increasing,the emission intensities of 5D0→7F0,1,2 transitions of Eu3+ ions decreased and the transition lines showed a red shift.The relative luminescence intensity ratio of 5D0→7F2 to 5D0→7F1 transitions decreased with increasing pressure,indicating lowering asymmetry around Eu3+ ions.During compression,structural transformation for cores in the present core-shell Eu3+:Y2O3/SiO2 sample from cubic to monoclinic took place at 7.5 GPa,and then the monoclinic structure turned into hexagonal above 15.2 GPa.After the pressure was released,the hexagonal structure transformed back to monoclinic and the monoclinic structure was kept stable to ambient pressure.     

Facile synthesis of visible light excited La_1-xGd_xF₃:Eu³⁺ micro-meter sphere using polyvinylpyrrolidone as a template

Lanthanide fluorides exhibited unique luminescent properties in terms of their low phonon energy can restrict the luminescence quenching and extend luminescent lifetimes.Here,a room-temperature co-precipitation method was used to synthesize europium(III) activated La1-xGdxF3 solid phosphors.X-ray diffraction(XRD) data confirmed the crystalline phases of synthesized sample belongs to orthorhombic system.All the as-derived materials exhibited red luminescence(5D0→7F1) under the excitation at longer wavelengths(394 and 466 nm).The powder with the most intense emission was achieved in terms of 10 mol.% doping concentration(Eu content,La/Gd=1/9) and sample sintered at 700 oC.Scanning electron microscopy(SEM) investigated the morphology and crystalline of the samples,showing that many regular and large balls(5-10 μmol/L) were dispersed within the micro-meter scale composites.We proved that the above crystal growth structures were controllable and predicable based on the surface functionalization by polyvinylpyrrolidone ligand.     

Luminescence properties of BaAl₁₂O₁₉:Tb,Ce and energy transfer between Ce³⁺,Tb³⁺

BaAl12O19:Tb,Ce phosphors were prepared by sol-gel technique,the crystalline structures of samples characterized by XRD,and the luminescence properties and energy transfer between Ce3+ and Tb3+ were investigated.The results indicated that the emission intensity and the excitation wavelength range of Tb3+ increased when Ce3+ was doped.It demonstrated that the Ce3+ added in the BaAl12O19:Tb could deliver energy to Tb3+,and Ce3+ was not luminous by itself.The relative emission intensity of Tb3+ at wavelength of 548 nm was the strongest by Tb3+/Ce3+ ratio of 2:1,when excited at 310 nm,which was the characteristic adsorption wavelength of Ce3+.     

Synthesis of well oil-dispersible BaYF₅:Yb³⁺/Er³⁺ nanocrystals with green upconversion fluorescence

Nearly monodisperse,regular-shaped and well oil-dispersible tetragonal BaYF5:0.2Yb3+/0.02Er3+ nanocrystals(NCs) were synthesized in water-ethanol-oleic acid-sodium oleate system.The as-obtained NCs exhibited bright upconversion(UC) fluorescence under the 980 nm excitation.Blue(2H9/2-4I15/2),green((2H11/2,4S3/2)-4I15/2) and red(4F9/2-4I15/2) transitions were observed.The results indicated that the relative intensity of green to red increased gradually with increasing power density,which were seldom in the previous work.Therefore,the UC properties and mechanism were studied in detail.     

Intense blue-emitting Ca₂PO₄Cl:Eu²⁺ phosphor for near-ultraviolet converting white light-emitting diodes

A blue phosphor Ca2PO4Cl:Eu2+(CAP:Eu2+) was synthesized by solid state reaction.The Ca2PO4Cl:Eu2+ exhibited high quantum efficiency and excellent thermal stability.The luminescent intensity of Ca2PO4Cl:Eu2+ was found to be 128% under excitation at 380 nm,149% under 400 nm,and 247% under 420 nm as high as that of BaMgAl10O17:Eu2+.The optimal doping concentration was observed to 11 mol.% of CAP:Eu2+.The energy transfer between Eu2+ ions in CAP were occurred via electric multipolar interaction,and the critical transfer distance was estimated to be 1.26 nm.A mixture of blue-emitting Ca2PO4Cl:Eu2+,green-emitting(Ba,Sr)2SiO4:Eu2+ and red-emitting CaAlSiN3:Eu2+ phosphors were selected in conjunction with 400 nm chip to fabricate white LED devices.The average color-rendering index Ra and correlated color temperature(Tc) of the white LEDs were found to be 93.4 and 4590 K,respectively.The results indicated that it was a promising candidate as a blue-emitting phosphor for the near-UV white light-emitting diodes.     

Luminescent properties of Eu³⁺-doped BaZrO₃ phosphor for UV white light emitting diode

A novel orange phosphor Eu3+ doped barium zirconate(BaZrO3) was synthesized by conventional solid state reaction method and its crystal structure and luminescent properties were investigated in this paper.The X-ray diffraction patterns(XRD) showed that simple BaZrO3 phase was obtained.Monitoring at 596 nm,the excitation spectrum consisted of a broad band and a series of narrow bands and the stronger excitation peaks located at 275 and 393 nm,respectively.The emission spectrum excited by 393 nm UV light was composed of four narrow bands.The strongest emission was located at 596 nm.The appropriate concentration of Eu3+ was 0.025(molar fraction) for the highest emission intensity at 596 nm.The H3BO3 and ammonium were added as flux and the results showed that 2 wt.% NH4F ions was the optimal flux for BaZrO3:Eu3+.     

Study on spectroscopic properties of GdOBr:RE3+ (RE=Eu, Tb, Ce)

Rare earth ions doped gadolinium oxybromide phosphors GdOBr:RE3 (RE=Eu, Tb, Ce) were synthesized by the method of solid-state reaction at high temperature, and the VUV-VIS spectroscopic properties of the phosphors were systematically investigated. Under the excitation of VUV or UV source, the phosphors doped with Eu3 and Tb3 show a bright and sharp emission at around 620 nm corresponding to the forced electric dipole 5D0→7F2 transition of Eu3 , and at around 544 nm corresponding to the 5D4→7F5 transition of Tb3 , respectively. For GdOBr:Ce3 , a broader and intense emission spanned 370-500 nm corresponding to the d-f transition of Ce3 was observed. The excitation spectra were also analyzed.     

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.     

Size dependence of up-conversion luminescence of NaYF₄:Yb³⁺/Tm³⁺

Tm3+/Yb3+ codoped NaYF4 microcrystals were synthesized using a hydrothermal method.The bright upconversion light was observed under 980 nm excitation.The upconversion luminescence was systematically investigated at different Yb3+ concentrations and different reaction temperatures and time.The sample with 60% Yb3+ concentration and reacting at 180 oC for 24 h possessed the highest luminescent efficiency.The higher luminescent efficiency was contributed to a large surface area.The large surface area induced the large vibration mode by absorbed H2O and CO2.The larger vibration mode could enhance the energy transfer efficiency from the excited Yb3+ to Tm3+ by the process of phonon assisted energy transfer.     

Photoluminescence properties of LaF3：Eu^3＋ nanoparticles prepared by refluxing method

The europium-doped LaF3 nanoparticles were prepared by refluxing method in glycerol/water mixture and characterized with X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), UV-vis diffuse reflectance spectrum, and photoluminescence spectra. The results of XRD indicated that the obtained LaF3: Eu3+ nanoparticles were well crystallized with a hexagonal structure. The FE-SEM image illustrated that the LaF3: Eu3+ nanoparticles were spherical with an average size around 30 nm. Under irradiation of UV light, the emission spectrum of LaF3: Eu3+ nanoparticles exhibited the characteristic line emissions arising from the 5D0→7FJ (J=1, 2, 3, 4) transitions of the Eu3+ ions, with the dominating emission centered at 590 nm. In addition, the emissions from the 5D1 level could be clearly observed due to the low phonon energies (-350 cm-1) of LaF3 matrix. The optimum doping concentration for LaF3: Eu3+ nanoparticles was determined to be 20mol.%.     

Energy transfer in Tb~（3＋）,Yb~（3＋） codoped Lu_2O_3 near-infrared downconversion nanophosphors

Tb3+ and Yb3+ codoped Lu2O3 nanophosphors were synthesized by the reverse-strike co-precipitation method. The obtained Lu2O3:Tb3+,Yb3+ nanophosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectra. The XRD results showed that all the prepared nanophosphors could be readily indexed to pure cubic phase of Lu2O3 and indicated good crystallinity. The Tb3+→Yb3+ energy transfer mechanisms in the UV-blue region in Lu2O3 nanophosphors were investigated. The experimental results showed that the strong visible emission around 543 nm from Tb3+ (5D4→7F5) and near-infrared (NIR) emission around 973 nm from Yb3+ (2F5/2→2F7/2) of Lu2O3:Tb3+,Yb3+ nanophosphors were observed under ultraviolet light excitation, respectively. Tb3+ could be effectively excited up to its 4f75d1 state and relaxed down to the 5D4 level, from which the energy was transferred cooperatively to two neighboring Yb3+. The Yb3+ concentration dependent luminescent properties and lifetimes of both the visible and NIR emissions were also studied. The lifetime of the visible emission decreased with the increase of Yb3+ concentration, verifying the efficient energy transfer from the Tb3+ to the Yb3+. Cooperative energy transfer (CET) from Tb3+ to Yb3+ was discussed as a possible mechanism for the near-infrared emission. When doped concentrations were 1 mol.% Tb3+ and 2 mol.% Yb3+, the intensity of NIR emission was the strongest.     

溶胶-凝胶法制备Sr2SiO4:Tb3+绿色荧光粉及其发光性能

采用溶胶-凝胶法合成了一系列适合紫外-近紫外激发的(1-X)Sr₂SiO₄:XTb3+(X=0,0.01,0.02,0.03,0.04,0.05,0.06)绿色荧光粉,并采用X射线衍射(XRD)、扫描电子显微镜(SEM)和荧光光谱(PL)研究了样品的结构及发光性能.由XRD的检测结果可知,合成样品属于单斜晶系的β-Sr₂SiO₄相.由SEM图可知,所有样品都呈无规则块状结构.当监测波长为546 nm,样品的激发光谱的主峰位于370 nm处,属于Tb3+的4f-4f特征跃迁吸收.当激发波长分别为285 nm和250 nm,所有样品在488 nm,547 nm,586 nm,623 nm处都出现了1个强发射峰,分别对应Tb3+的5D₄→7F₆、5D₄→7F₅、5D₄→7F₄和5D₄→7F₃电子跃迁.最强发射峰位于547 nm处,呈现特征为绿光发射.随Tb3+掺杂量增大,发射强度呈现出先增大后减小的变化趋势,即存在浓度猝灭效应.当Tb3+掺杂量为X=0.03时,样品的发光强度最大.      

Synthesis and luminescence characteristics of terbium（III） activated NaSrBO3

The thermoluminescence (TL) and photoluminescence (PL) properties of the phosphor NaSrBO 3 :Tb 3+ were reported and discussed. The combustion technique was used for the synthesis of polycrystalline samples of NaSrBO 3 :Tb 3+ . The TL glow curve of the compound had a simple structure with a single peak at 434 K. TL sensitivity of the phosphor was found to be more than that of (LiF:Mg,Cu,P). The TL glow curve was studied as a function of concentration of dopant and dose of gamma ray irradiation. The kinetic parameters of the thermoluminescence of NaSrBO 3 : Tb 3+ were calculated employing the peak shape method. The photoluminescence (PL) properties of Tb 3+ doped in NaSrBO 3 were studied over the 200-400 nm excitation range. The excitation spectra of NaSrBO 3 :Tb 3+ consisted of single narrow band peaking at about 236 nm. The emission spectra monitored at 236 nm excitation consisted of a series of sharp lines peaking at 489, 544, 586 and 622 nm corresponding to the 5 D 4 → 7 F j (j=3,4,5,6) transitions within the 4f 8 configurations of Tb 3+ .     

New Green Phosphors Ba（1-x）SrxZr（BO3）2 Doped with Tb^3＋ for PDP Applications

Thephosphorsusedinplasmadisplaypanel(PDP)deviceshouldemitvisiblelightundervacuum ultraviolet(VUV)excitationof147nmand or172nm fromXe Hegasplasma[1].Recentlylotsoftraditional lampphosphorshavebeenusedascommercialphos phorsforPDP.However,thesematerialsstill…     

Synthesis and Characteristic of Poly（N-vinylacetamide） Containing Terbium Ion

Insulatinghostsdopedwithrareearthionsfinda widevarietyofapplication[1].Particularly,materials thathavefluorescentpropertiesarenotonlyattractive subjectsofresearch,butalsoimportantmaterialsfor manytechnologicaldevices.Rareearthdopedinor ganiccrystalsaresu…     

Synthesis, Characterization and Fluorescence of Rare earth Nitrate Complexes with Triaza-crown Ether Derivative

Sinceaza crownethershowsspecialcoordinationpropertiestotransitionmetalandheavymetalions[1,2 ] ,therearemanyreportsofthecomplexesinhost guestchemistry ,molecularrecognition[3 ,4] andionophoreinmembranetransportation[5] ,butthereislittlereportontheirrareearthscomplexesandthefluorescenceaboutthecomplexes[6] ,andthefluorescenceintensityoftheircomplexesarenotverystrong .Weinsetbenzoylgroupintothemacrocycle ,expectingthatitsrareearthscomplexeshavebetterfluorescenceproperties .Inthispaperthesynthesis…     

Energy transfer from Tb³⁺ to Eu³⁺ in zinc lead borate glass

In order to sensitize the luminescence of Eu3+ ions in heavy metal glass,zinc lead borate glass samples containing various concentrations of Eu3+ and Tb3+ ions were prepared to study the Tb3+ to Eu3+ non-radiative energy transfer phenomena.Energy level structures of Tb3+ and Eu3+ ions were plotted to show the excitation and energy transfer routes.Efficient energy transfer from Tb3+ to Eu3+ was observed and studied qualitatively in terms of doping concentrations.The sensitization turned out to be less effective than expected.Further studies to characterize the oxidation of Tb3+ into tetravalent state and to examine the mechanism of energy transfer are proposed.     

Controlled synthesis and tunable luminescence of NaYF₄:Eu³⁺

High quality NaYF4:Eu3+ luminescent materials were successfully synthesized via a facile template technique by hydrothermal method.The samples were characterized by X-ray powder diffraction(XRD),transmission electron microscopy(TEM) and fluorescence spectroscopy(FS).The incorporating of Eu3+ ions into NaYF4 crystal lattice influenced the symmetry types of NaYF4 crystals,resulting in phase transformation of NaYF4 crystals between α and β phase.The pure hexagonal phase of branched NaYF4:Eu3+ was obtained as the Eu3+ concentration reached 15 mol.%.In addition,the luminescence color was tuned by changing the doping concentration of Eu3+ ions.     

LiZnPO4：Tb^3＋,Ce^3＋ green phosphors with high efficiency

Tb3+ and Ce3+ co-activated LiZnPO4 phosphors with high luminescence efficiency were synthesized by a high temperature solid-state reaction at 1000 oC for 3 h. The XRD patterns, photoluminescence spectra and SEM were recorded and the effects of Tb3+ and Ce3+ concentration, sintering condition on the luminescent properties of as-synthesized phosphors were investigated. The emission spectra under ultraviolet (200-300 nm) radiation showed a dominant peak at 543 nm attributed to the 5D4→7F5 transition of Tb3+, which was greatly en-hanced by the co-doping of Ce3+, indicating that there occurred an efficient non-radiative energy transfer from Ce3+ to Tb3+. The optimal dop-ing concentrations of Tb3+ and Ce3+ were determined to be 9% and 10%, respectively.