Synthesis and luminescence properties of Sr3-z（AlxSi1-x）O5-xFx：zCe^3＋phosphors

Sr3-z(Alx,Si1-x)O -5-xFx:zCe3+ phosphors were synthesized by high-temperature solid-state reaction.The structure and luminescence properties of phosphors with various Al/Si ratios and Ce3+ concentrations were characterized using various methods such as X-ray diffraction,photoluminescence excitation and photoluminescence spectra.XRD result displayed that a complete solid solution between Sr3AlO4F and Sr3SiO5 was formed.With the increasing of x value,a broader excitation band and stronger absorption appeared in the blue light region.Moreover,the emission band shifted to a shorter wavelength and the emission intensity reached a maximum at x=0.6.By adjusting the concentration of Ce3+,a widely tunable range of emission wavelength under the excitation of 460 nm was obtained from the green to yellow regions.In addition,the concentration and thermal quenching were also discussed.     

Enhancement of red to orange emission ratio of YPO4：Eu3＋,Ce3＋ and its dependence on Ce3＋ concentration

Eu3+ and Ce3+ co-doped YPO4 microspheres were synthesized by hydrothermal method without template. The emission spectra showed that the red emission centered at 618nm could be readily increased relatively to the orange emission centered at 590nm by controlling the doping concentration of Ce3+ ion. The investigation based on excitation spectra and decay curves demonstrated that the doped Ce3+ ions took two efficient energy transfers to Eu3+ ions and affected the lifetime of the emission states of Eu3+ ions so that the emission spectra of Eu3+ ion were accordingly tuned with the Ce3+ content increasing. This controllable red (5D0→7F2) to orange ( 5D0→7F1) emission ratio of YPO4:Eu3+,Ce3+ made it very promising for encoded anti-fake labels and bio-labels.     

Eu2＋ and Dy3＋ codoped （Ca,Sr）7（SiO3）6Cl2 highly efficient yellow phosphor

Eu2+ and Dy3+ codoped(Ca,Sr)7(SiO3)6Cl2 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and photoluminescence spectra. The as-prepared phosphor showed a broad emission spectrum centered at 550 nm for Eu2+single-doped phosphor, while located at 548–544 nm for the Eu2+, Dy3+ codoped samples under excitation at 380 nm light. The emission intensity was greatly improved when Dy3+ was doped into the(Ca,Sr)7(SiO3)6Cl2:Eu2+ system. The composition-optimized sample with 3 mol.% of Dy3+ and constant 10 mol.% of Eu2+ exhibited a 220% PL enhancement compared to the phosphor with 10 mol.% Eu2+ single-doped. Meanwhile, it was found that the quantum efficiency of phosphor namely(Ca,Sr)7(SiO3)6Cl2:3 mol.% Dy3+, 10 mol.% Eu2+ could get up to 24.6%. The synthesized yellow-emitting(Ca,Sr)7(SiO3)6Cl2:Dy3+,Eu2+ is a promising candidate as high-efficiency yellow phosphor for NUV-excited white LEDs.     

Enhanced photoluminescence properties of （Y,Bi） BO_3：RE~（3＋） （RE=Eu,Tb） phosphors synthesized at low temperature

Eu3+ or Tb3+ doped Y(1-x)BixBO3 (0.1≤x≤0.4) phosphors were synthesized using the simple solid state method at low temperature from 700 to 870 ℃. The analysis of the X-ray diffraction (XRD) indicated that the system of Y(1-x)BixBO3 (0.1≤x≤0.4) had the same structure as that of YBO3. The excitation spectra, emission spectra and decay lifetimes of all samples were measured in detail. All the samples exhibited characteristic luminescence of Eu3+ or Tb3+. Y0.65Bi0.2Eu0.15BO3 and Y0.8Bi0.1Tb0.1BO3 samples had the...     

Characterization of optical transitions of Eu~（3＋） in lanthanum oxychloride nanophosphor

This paper presented the studies on the optical properties and calculation of spectral parameters of europium doped lanthanum oxychloride nanophosphor for their possible applications in optoelectronic devices. The compound was doped with 0.1 mol% Eu3+ ions. The X-ray diffraction study of prepared sample suggested the tetragonal structure with particle size in the range of 18-21 nm. The photoluminescence (PL) emission spectra showed the bright emission in orange-red region from 580 to 630 nm. The most intense emission peak at 621 nm was due to transition 5D0→7F2 in energy levels of Eu3+ ions. The spectral parameters were calculated from the absorption and emission spectra using Judd-Ofelt intensity parameters. The calculated values of the oscillator strength corresponding to the three transitions 7F1→5D1, 7F1→5D2 and 7F0→5D2 observed at 535, 472 and 465 nm in absorption spectra were 0.30×10-6, 1.36×10-6 and 0.63×10-6, respectively. The value of transi- tion probability (A), stimulated emission cross-section ( ) and radiative lifetime (τrad) corresponding to 621 nm emission peak (transition 5D0→7F2) were 308 s-1, 1.22×10-21 cm2 and 3.24×10-3 s, respectively.     

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,structural and optical properties of SrZrO3：Eu3＋phosphor

Eu3+ activated Sr1–xEuxZrO3(x=0.01–0.04) phosphor with perovskite structure was successfully synthesized by using combustion method.The structure,morphology and optical properties of the material were characterized by X-ray diffraction,scanning electron microscopy and fluorescence spectrometry.The XRD results indicated that crystals of SrZrO3:Eu3+ belongs to tetragonal perovskite system.The phosphor could be effectively excited by UV light and the emission spectra results indicated that reddish-orange luminescence of SrZrO3:Eu3+ due to magnetic dipole transition 5D0→7F1 at 593 nm was dominant.Thus,the prepared phosphor showed remarkable luminescent properties which find applications in field emission display(FED) and plasma display panel(PDP) devices.     

Preparation and Luminescence Properties of the New Long Phosphorescent Phosphors Ba1-x Cax Al2O4 ： Eu^2＋ , Dy^3＋

New long phosphorescent phosphors Ba1-x CaxAl2O4:Eu^2 , Dy^3 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 Thermolumineseence spectra were measured to investigate the traps created by the doping of Dy^3 .     

Synthesis and spectral characteristics of La2MoO6：Ln3＋ （Ln=Eu, Sm, Dy, Pr, Tb） polycrystals

The novel phosphors of La 2 MoO 6 activated with the trivalent rare earth Ln 3+ (Ln=Eu, Sm, Dy, Pr, Tb) ions were synthesized by solid state reactions at high temperature in air atmosphere, and their phase impurities and luminescent properties were studied. The photoluminescence (PL) excitation and emission spectra, and decay curves were employed to study their luminescence properties. The lifetimes of the characteristic emissions from Ln 3+ ions were in the order of millisecond except Pr 3+ ions. (LaEu 1-x ) 2 MoO 6 was a promising phosphor for practical application and the optimum concentration was x=0.075. The concentration quenching mechanism of Eu 3+ was also discussed by theoretical fitting using Burshtein model.     

Luminescent properties of MMgP_2O_7：Eu~（3＋）（M=Ca,Sr,Ba） phosphor

A series of red phosphors Eu3+-doped MMgP2O7(M=Ca,Sr,Ba) were synthesized by solid-state reaction method.X-ray powder diffraction(XRD) analysis confirmed the formation of pure CaMgP2O7,SrMgP2O7 and BaMgP2O7 phase.Photoluminescence spectra of MMgP2O7(M=Ca,Sr,Ba):Eu3+ phosphors showed a strong excitation peak at around 400 nm,which was coupled with the characteristic emission(350-400 nm) from UV light-emitting diode.The CaMgP2O7:Eu3+,SrMgP2O7:Eu3+ and BaMgP2O7:Eu3+ phosphors showed strong emission bands peaking at 612,593 and 587 nm,respectively.Due to the difference of the ion sizes between Ba2+(0.142 nm),Sr2+(0.126 nm),Ca2+(0.112 nm),Mg2+(0.072 nm) and Eu3+(0.107 nm),Eu3+ ions were expected to substitute for different sites in CaMgP2O7,SrMgP2O7 and BaMgP2O7 lattice.     

Effect of Y3＋, Gd 3＋and La3＋dopant ions on structural,optical and electrical properties of o-mullite nanoparticles

Dielectric ceramics of M(x) Al6(1–x) Si2 O13 doped mullite were synthesized via co-precipitation technique. The X-ray diffraction profiles revealed that these nanoparticles were crystallized well and the volume of mullite unit cell was increased as a function of the ionic radius of dopant ion. TEM images showed regular orthorhombic crystal morphology for the pure mullite sample. Meanwhile, the doped samples exhibited slightly distorted crystal morphology of larger particle sizes. DSC thermograms evinced that the exothermic peak temperature of mullite was shifted to the lower value with M3+ion insertion. The photoluminescence spectra were studied for mullite samples, and it was found that the intensity of the emission spectra was affected by the M3+ion type. It was found that, Y3+doped mullite achieved the minimum dielectric loss value of 0.01 in the radio wave frequency region(1 MHz). Meanwhile, Gd3+ doped mullite achieved the minimum dielectric loss value of 0.09 in the microwave frequency region(1 GHz).     

Luminescence properties of Eu3＋ and Ho3＋ in SreTiO4

Eu3+ and Ho3+ doped Sr2TiO4 were synthesized by using solid-state reactions. Samples sintered at 1300 oC for 6 h could be indexed to Sr2TiO4 with a single phase. Eu3+ in Sr2TiO4 emitted orange light under the excitation at 365 nm in a broad band which was coupled well with the strongest emission of high pressure mercury vapor lamps. Ho3+ in Sr2TiO4 emitted yellow light under blue excitation from 450 to 460 nm which agreed well with the emission of blue InGaN-based light-emitting diodes. The present results indicated that Sr2TiO4 was a promising host for high pressure mercury vapor lamps or white light-emitting diodes.     

Photoluminescence of BaGdB9O（16）：Eu^3＋ co-doped Al^3＋ or Sc^3＋ under UV-VUV excitation

Single phase of BaGd0.9-xMxEu0.1B9O16 (M=Al or Sc, 0≤x≤0.3) powder was prepared by the solid-state reaction and its photoluminescence (PL) properties were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation. Monitored with 613 nm emission, the excitation spectra of BaGd0.9-xMxEu0.1B9O16 consisted of three broad bands peaking at about 242, 208, and 142 nm, respectively. The one at about 242 nm originated from the charge transfer band (CTB) of O2-→Eu3+. The other two were assigned to the absorption of the host, which was overlapped with absorptions among borate groups, f→d transition of RE3+ (RE=Gd, Eu), and the charge transfer transition of O2-→Gd3+. The maximum emission peak was observed at about 613 nm in the emission spectra of BaGd0.9-xMxEu0.1B9O16 under both 254 and 147 nm excitation, which originated from the electric dipole 5D0→7F2 transition of Eu3+. When excited with 254 nm, the integral emission intensity of Eu3+ increased after Al3+ or Sc3+ substituting Gd3+ partly in BaGd0.9Eu0.1B9O16. Under 147 nm excitation, the integral emission intensity of Eu3+ decreased after some Gd3+ was replaced by Sc3+, but increased after adding appropriate Al3+ into BaGd0.9Eu0.1B9O16.     

Luminescence properties of red phosphors Ca_（10）Li（PO_4）_7：Eu~（3＋）

A series of red phosphors Ca10Li (PO4)7:Eu3+ were synthesized by high temperature solid-state reaction method. Their luminescence properties were characterized by means of photoluminescence excitation and emission spectra,CIE chromaticity and quantum efficiency. Results indicated that the phosphors could be effectively excited by the near ultraviolet (NUV) light (393 nm). The main emission peaks of the phosphor were ascribed to the transition 5D0-7F2 (613 and 617 nm) of Eu3+ ion when samples were excited by...     

Preparation and luminescent properties of MgTiO3：Eu3＋ phosphor for white LEDs

A novel red phosphor Eu3+ doped magnesium titanate (MgTiO3) was synthesized via sol-gel method. The X-ray diffraction patterns (XRD) revealed that a pure MgTiO3 phase was obtained. Its excitation spectrum consisted of a broad band (<350nm) and a series of narrow bands in the long wavelength, and the strongest excitation peak at 465nm might be exited by GaN-chip to emit red light for white LED. The phosphors showed strong emission at 614nm which could be attributed to the 5D0→7F2 emission of Eu3+ . The emission intensity of MgTiO3:Eu3+ phosphor reached the maximum at the Eu3+ concentration of 3.5mol.%. The luminescent properties (such as emission intensity and decay times) were further improved by introducing Al3+ as a charge compensator, demonstrating potential applications in white LED.     

Luminescence Properties of Green-Emitting Phosphor （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ for White LEDS

The （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ green-emitting phosphors were synthesized by conventional solid-state reaction in a CO-reductive atmosphere, and their luminescent properties were investigated. The XRD data show that the Ba/Sr ratio not only affects the lattice parameters, but also influences the emission peak. The excitation spectra indicate that this phosphor can be effectively excited by UV light from 370 to 470 nm. The emission band is due to the 4f^65d^1→4f^7 transition of the Eu^2＋ ion. With an increase in x, the emission band shifts to longer wavelength and the reason was discussed. The emission spectra exhibit a satisfactory green performance under different excitation wavelength（380,398,412,420,460 nm）. （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ is a promising phosphor for green white-lighting-emission diode by ultraviolet chip.     

Luminescence properties of YAl3（BO3）4 phosphors doped with Eu^3＋ ions

YAl3 （BO3）4： Eu^3＋ 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： Eu^3＋ phosphors with concentration of Eu^3＋ 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 region. 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： Eu^3＋ phosphors was 8 mol%.     

Synthesis of ZnO：Dy Nanopowder and Photoluminescence of Dy^3＋ in ZnO

A type of dysprosium-doped ZnO （ZnO：Dy） nanopowder was synthesized by high temperature calcinations. XRD was used to analyze the structure. Photoluminescence spectra were used to study the optical characteristic. PL of ZnO：Dy shows two different spectra which are broad band resulted from the defect of Dy in ZnO and sharp lines from the 4f→4f transition of isolated Dy^3 ＋ luminescence center. The emission and excitation spectra depend on the excitation wavelength and the concentration of Dy^3＋ . The broad bands with peaks at 600 and 760 nm are attributed to the recombination from an electron of the defect Dy in ZnO to a hole in VB.     

Syntheses and Characterization of Binuclear Complexes Tb（1-x）Eux（TTA）3 Phen

Rare earth ternary complexes Tb1-xEux（TTA）3Phen（x=0,0.25,0.5,0.75,1.0）were synthesized and characterized by DTA-TG,XRD and infrared（IR）.The photophysical properties of these complexes were studied in detail using ultraviolet absorption spectra and fluorescent spectra.Ultraviolet absorption showed that the energy absorption of the complexes mostly came from ligands.Infrared spectra of Tb1-xEux（TTA）3Phen complexes were similar to the pure complexes.TG curves proved that the complexes were stable.Tb3＋ emission was almost quenched and the Eu3＋ emission was enhanced by codoping the complexes.The Tb3＋ ion acted as an energy transfer bridge that helped energy transfer from poly（N-vinylcar-bazole（PVK）to Eu3＋.In addition,their PL and EL properties were systematically studied.     

Luminescent properties of Eu~（3＋） doped Gd_2WO_6 and Gd_2（WO_4）_3 nanophosphors prepared via co-precipitation method

Eu3+ doped Gd2WO6 and Gd2(WO4)3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The emission spectra and excitation spectra of samples were measured. J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated, and the concentration quenching of Eu3+ luminescence in different matrixes were studied. The results indicated that effective Eu3+:5D0-7F2 red luminescence could be achieved while excited by 395 nm near-UV light and 465 nm blue light in Gd2WO6 host, which was similar to the familiar Gd2(WO4)3:Eu. Therefore, the Gd2WO6:Eu red phosphors might have a potential application for white LED.