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.     

Characterization of (Y,Gd)B_xV_(1-x)O_(4-x)∶Eu Phosphor Prepared by Coprecipitation Reaction

The PDP have been widely used for large flatpanel displays.Phosphors for the application in PDPare required to have high conversion efficiency by theVUVradiation of147and/or172nmfromthe Xe andXe-He gas plasma[1].In order to have a good picturequality,much attention has been paid to i mprove ordevelop novel PDP phosphors[2~6].The commercialred emitting PDP phosphor(Y,Gd)BO3∶Eu3+showsthree sharp emissions peaked at593,612and627nm,which are corresponding to the transitions of5D0→7F1,5…     

Study on （Y, Gd）3（Al, Ga）5O12：Ce^3＋ Phosphor

(Y1-a,Gda ) 3 - x (Al1-b, Gab) 5O12 : Cex^3 was synthesized by high-temperature solid state reaction in reducing atmosphere based on high purity raw materials. The influences of y^3 , Gd^3 , A1^3 , Ga^3 and activator-Ce^3 on the performance of the phosphor were investigated. Ce^3 is the luminescent center and activates the phosphor after it replaces Y partially. When x is less than 0.12, the volume of the crystal and the emission intensity of the phosphor increase with the quantity of Ce^3 . When CeO2 is added too much, the phase CeAlO3 will appear. The excitation and emission peaks of the phosphor will shift to longer wavelength when the amount of Gd^3 increases. The wavelength of the emission peak can shif tabout 20 nm when a equals 0.45. In opposite, the excitation and emission peaks will shift to shorter wavelength, when part of Al^3 is replaced by Ga^3 . The wavelength of the emission peak can shift about 20 nm when b equals 0.55.Through the replacemeat of Y^3 or Al^3 by Gd^3 or Ga^3 , the emission peak of the phosphor can be adjusted from 520 to 560 nm. In this way, the phosphor is more suitable for different chips.     

Luminescence of Eu^3 ＋ in LnAlO3 （Ln = Gd, Y） under UV and VUV Excitation

Single phases of LnAlO3 : Eu^3 ( Ln = Gd, Y ) were obtained by the process of evaporation of their nitric acid solution, and then pyrolysis of their nitrate salts. On monitoring by 613 nm emission, broad bands at around 270 and 170nm were observed in the excitation spectrum of Gd0.95Eu0.05AlO3. These peaks could be assigned to charge transfer (CT)transitions of Eu^3 -O^2- and Gd^3 -O^2- respectively. All the transitions observed in Gd0.95Eu0.05AlO3 are faithfully reproduced in the Y0.95Eu0.05AlO3, but with an exception of the ^8S7/2→^6I11/2 transition of Gd^3 . The 153 nm broad band could be the CT transition of Y^3 -O^2 - . Accordingly, the efficiency luminescence of (Gd, Y) BO3 : Eu^3 was explained as a result of CT transitions of Gd^3 -O^2- and Y^3 -O^2- under 147 nm excitation. Under VUV excitation, Gd0.95Eu0.05AlO3 exhibits a bright red luminescence with CIE chromaticity coordinates of (0.623, 0. 335) with a PL intensity of 30 of the commercial phosphor (Gd, Y) BO3 : Eu^3 (KX-504A). The PL spectrum of Y0.95Eu0.05AlO3 is similar to that of Gd0.95Eu0.05AlO3. Calculation of the color coordinates gives x = 0. 636, y = 0. 340 with a PL intensity of 50 of the (Gd, Y) BO3 : Eu^3 ( KX-504A) for Y0.95Eu0.05AlO3, and confirms that it has the appearance of pure spectral red, corresponding approximately to 608 nm. It can be concluded that LnAlO3:Eu^3 is a promising red VUV phosphor.     

Preparation, Structural Analysis and Luminescence Properties of Nanocrystalline Phosphor Gd203 ： Eu

Nanocrystalline monoclinic and cubic Gd2O3:Eu with different Eu^3 concentration were prepared using glycinenitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, pure monoclinic and cubic Gd203:Eu with particle size less than 40 nm can be easily formed. Under ultraviolet excitation, main emission of Eu^3 (^5D0→^7F2) locates at 624 nm in monoclinic Gd2O3:Eu and 611 nm in cubic sample, In excitation spectrum two broad bands corresponding to the host absorption and charge transfer state (CTS) and f-f transitions of Gd^3 and Eu^3 were observed and discussed. The quenching concentration of monoclinic and cubic Gd2O3:Eu is 10% and 15 %, respectively,both of which are much higher than that of bulk Gd2O3 : Eu.     

Eu^2＋ Luminescence in BaZnAl10O17 ： Eu Phosphor

Eu^2 -doped BaZnAl10O17 phosphor was successfully obtained by coprecipitation method, in which oxalic acid and ammonia were used as precipitants, and precipitates were calcined at 1400 ℃ for 3 h. Its luminescent intensity was much stronger than the one obtained by solid-state reaction at high temperature. According to XRD, the crystal was identified as BaZnAl10O17 with β-Al2O3 structure.     

（Zn, Ca） Solid-Solution Behavior and Its Effect on Luminescence Properties in Ca1-x Znx TiO3 ： 0.002Pr^3＋ Phosphors

Nominal composition of Ca1-xZnxTiO3 ： 0. 002Pr^3 ＋ （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-xZnxTiO3：0.002Pr^3＋ phosphors. The effect of solid-solution structure formed by substitution between Ca^2 ＋ and Zn^2＋ 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- xZnxTiO3：0.002Pr^3＋ 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 Ca^2＋ and Zn^2＋ ions has significant effect on the luminescence properties of single phase Ca1-xZnxTiO3：0.002Pr^3＋ phosphors.     

Luminescence Properties of （ Y, Gd） Al3 （BO3） 4 ： Eu^3＋ under VUV excitation

(Y, Gd)Al3 (BO3)4:Eu^3 samples were prepared by the conventional solid state reaction. The XRD results indicate that the crystal symmetry is low. The excitation spectrum is composed of two broad bands centered at about 170 and 250 nm respectively. In the emission spectra, the peak wavelength is about 616 nm under 147 nm VUV excitation. The luminescent chromaticity coordinate and the relative intensity change along with Gd^3 mole concentration in the range of 0.15 to 0.85 mol (and Eu^3 mole concentration, 0.02 to 0. 1 mol). The correlative data show that the concentration quenching occurs when the Eu^3 mole concentration ranges from 0.02 to 0.1 mol, and the Gd^3 →Gd^3 , Gd^3 →Eu^3 and host→Eu^3 , Gd^3 energy transfers exist, and Gd^3 mole concentration influences Eu^3 emission.     

Characterization of Y2O2S： Eu^3＋, Mg^2＋, Ti^4＋ Long-Lasting Phosphor Synthesized by Flux Method

Long-lasting phosphor Y₂O₂S: Eu³⁺, Mg²⁺, Ti⁴⁺ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu₂O₃ content in Y₂O₂S: Eu_x³⁺ (0.01 ≤ x ≤ 0.10). On the other hand, the change of unit cell parameter a is not linear dependence. In the Y₂O₂S: Eu³⁺ crystal structure, Eu³⁺ ions only replaced Y³⁺ ions' places in which it posited center position of c axis. With the increase of Eu₂O₃ content, the position of the strongest emission peak changed from 540 nm (⁵D₁→⁷F₂ transition) to 626 nm (⁵D₀→⁷F₂ transition), and the maximum intensity was obtained when x = 0.09 in Y₂O₂S: Eu_x³⁺ (0.01 ≤ x ≤ 0.10). This is due to the environment of trivalent europium in the crystal structure of Y₂O₂S. Doping with Mg²⁺ or Ti⁴⁺ ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg²⁺ and Ti⁴⁺ ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence (LLP) was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye (0.32 mcd · m⁻²). Thus the LLP mechanism was analyzed.     

Study on Luminescence Properties of High-Density Phosphors BiTaO4：Pr^3＋ and BiTaO4

The photoluminescence properties of BiTaO4:Pr^3 and BiTaO4 at room temperature were studied, and the infrared transmission and diffusion reflection spectra of BiTaO4 were measured. The photoluminescence spectrum of BiTaO4 peaks at about 420, 440 and 465nm. There has an obvious excitation band from 330 to 370nm. The photoluminescence spectrum of BiTaO4:Pr^3 consists of the characteristic emission of Pr^3 , and its main peak is at 606 nm from ^3P0→^3H6 transition of Pr^3 . Its excitation spectrum consists of the wide band with maximum at 325nm, the wide band in the range of 375-430nm, and the characteristic excitation of Pr^3 .The bands at 325nm and 375-430nm may be from the absorption of the charge transfer transition of the tantalate group and defect energy levels in its forbidden band, respectively.There is energy transfer from host to Pr^3 . Because both the host density and photoluminescence peak intensity of BiTaO4:Pr^3 are superior to PbWO4, BiTaO4:Pr^3 may be a potential heavy scintillator.     

Synthesis and Luminescence of Complexes EuxY1-x（phen）L3

A series of binuclear complexes with different molar ratio of europium to yttrium with cinnamic acid and o-phenanthroline were synthesized in anhydrous alcohol. Elemental analysis shows that the composition of the complexes areEuxY1-x(phen)L3(L: C6H5CH=CHCOO, x = 1.0, 0.7, 0.5, 0.3 and 0.1). The IR absorption spectra indicate that cinnamate is coordinated to the rare earth ions and chemical bonds are formed between rare earth ions and nitrogen atoms of o-phenanthroline. Fluorescent spectra show that the emission of Eu^3 ion can be greatly enhanced if some of europium ions in the complexes are substituted by yttrium ions.     

Photoluminescent and Electroluminescent Properties of Ligand Emitting y^3＋, La^3＋, Gd^3＋ and Lu^3＋ Complexes

The photolumineseent (PL) and eleetroluminescent (EL) properties of a series of ligand emitting rare earth complexes (including y^3 , La^3 , Gd^3 and Lu^3 ) were systematically studied. These complexes have the same anionic ligand, 1-phenyt-3-methyl-4-isobutyryl-5-pyrazoloneate (PMIP), and three neutral ligands, triphenyl phosphine oxide(TPPO), 2, 2‘-dipyridine (Bipy) and phenanthroline (Phen). Measured with 60 nm thin film of these complexes vaporized in vacuum on quartz substrates, a good regularity in the PL properties was observed. For rational comparison, the same structural EL devices based on these complexes, ITO/PVK (40 nm)/the complex (80 nm)/Mg: Ag (200 nm)/Ag (100 nm), were fabricated. Excluding the exeiplex emission happens, the EL luminance usually increases with the increasing of PL efficiency.     

Improvement of Luminescent Properties of PbWO4 by Doping with Gd3＋ Ions

The luminescent properties of PbW04: Gd3 were studied. The luminescence of Gd3 in PbWO4: Gd3 was quenched. It is possible that the excitation states of Gd3 locate in the conduction band of PbW04 crystal. The luminescent intensity of the green and the blue band of PbW04 emission increases by doping with about 0.005% and 0.01% (molar fraction) Gd3 respectively. Mechanism of this enhancement of PbWO4:Gd3 luminescence is probably due to energy transfer from Gd3 to PbW04 host in the crystal. The PbW04 doped with low concentration of Gd (about 0.005% -0.01% ) is a good scintillating material.     

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.