Luminescence and Preparation of LED Phosphor Ca8Mg （ SiO4）4Cl2 ： Eu^2＋

Calcium magnesium chlorosilicate doped by europium, Ca8Mg（SiO4）4Cl2： Eu^2＋, was prepared by the solid state reaction at high temperature. The compound obtained is pure Ca8Mg（SiO4）4Cl2 phase with cubic structure. Its average particle size is 5 μm, and it has good dispersity and morphological form. The excitation spectrum of Ca8Mg（SiO4）4Cl2： Eu^2＋ is a wide band, which covers from 270 to 480 nm. The emission spectrum is also a wide band peaked at 510 nm. The luminescent intensity reaches to the maximum when the concentration of Eu^2 ＋ is 2%. The wavelength of emission and excitation of the phosphor with various Eu^2 ＋ contents keeps constant. This spectrum range matches violet and blue LED chips very well, and its strong luminescence intensity is suitable for a green phosphor of tricolor phosphor of white light 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.     

Luminescent characteristics of Ba3Y2（BO3）4：Eu^3＋ phosphor for white LED

The Ba3Y2（BO3）4：Eu^3＋ phosphor was synthesized using a high temperature solid-state reaction method and the luminescent characteristics were investigated. The emission spectrum exhibited one strong red emission at 613 nm, corresponding to the electric dipole 5D0-TF2 transition of Eu^3＋, under 365 nm excitation. The excitation spectrum of 613 nm indicated that the Ba3Y2（BO3）n：Eu^3＋ phosphor was effectively excited by ultraviolet （UV） （254, 365 and 400 nm） and blue （470 nm） light. The effect of Eu^3＋ concentration on the 613 nm emission of the Ba3Y2（BO3）n：Eu^3＋ phosphor was measured. The results showed that the emission intensity increased with increasing Eu^3＋ concentration, and then decreased. The CIE color coordinates of Ba3Y2（BO3）4：Eu^3＋ phosphor were x=0.641 and y=0.359 at 15 mol.% Eu^3＋.     

Luminescence and Energy Transfer Properties of Ca2 Gd8 （SiO4 ）6O2：A（ A = Pb^2＋, Tm^3＋） Phosphors

Ca2Gd8 (SiO4 )6O2: A (A = Pb^2 , Tm^3 ) phosphors were prepared through the sol-gel process. X-ray diffraction(XRD), scanning electron microscopy( SEM )and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicate that the phosphors crystallized completely at 1000℃. SEM study reveals that the average grain size is 300～1000 nm. In Ca2Gd8 (SiO4)6O2: Tm^3 phosphors, the Tm^3 shows its characteristic blue emission at 456 nm(^1D2-^3F4 )upon excitation into its ^3H6—^1D2 (361 nm), with an optimum doping concentration of 1mol% of Gd^3 in the host lattices. In Ca2Gd8 (SiO4 )6O2: pb^2 , Tm^3 phosphors, excitation into the Pb^2 at 266 nm(^1Oo—^3P1)yields the emissions of Gd^3 at 311 nm(6p—^8S)and Tm^3 at 367 nm (^1D2-^3H6)and 456 nm (^1D2-^3F4 ), indicating that energy transfer processes of Pb^2 -Gd^3 and Pb^2 -Tm^3 have occurred in the host lattices.     

Synthesis and Luminescent Properties of Novel Red Long-Lasting Phosphor Ca2Zn4Ti15O36：Pr^3＋

A novel red long-lasting phosphor Ca2Zn4Ti15O36:Pr were synthesized by solid state reaction and by sol-gel method. It is a new type of Pr^3 -doped titanate red long lasting phosphor. It is difficult to make pure Ca2Zn4Ti15O36 crystalline by solid state reaction and it must be sintered at 1200℃ for 96 h.The analysis results of thermogravimetric curve and Xray powder diffraction revealed that Ca2Zn4Ti15O36 canbe formed by sintering precursor at 700℃ for 12 h,     

Spectral Properties and Upconversion Luminescence of Er^3＋, yb^3＋： BaWO4 Crystal

The optical quality of Er^3＋, yb^3＋： BaWO4 crystal was gown by Czochralski method. Absorption spectra were measured and energy levels were assigned. According to Judd-Ofelt theory, the spectral strength parameters of Er^3＋ ion were fitted to beΩ2 =0.3926 x 10^-20 cm^2, Ω4 =0.0721×10^-20 cm^2, Ω6 =0.0028 ×10.20 cm^2. Emission peaks centered at around 523,544 and 670 nm were observed under 334 nm He-Cd laser excitation and emission peaks centered at 1001 and 1534 nm were detected under 976 nm laser excitation. Strong green emission was also observed when the crystal was pumped with 808 nm and 976 nm laser. The mechanisms of frequency upconversion and sensitization were analyzed.     

Co-Precipitation Synthesis and Spectral Characteristics of Long Afterglow Phosphor Y2O2 S： Sm^3＋, Mg^2＋ , Ti^4＋

Y2O2S：Sm^3＋, Mg^2＋, Ti^4＋ phosphor was synthesized by co-precipitation method. The crystalline structure of all synthesized phosphors was investigated by XRD. The result showed that all synthesized phosphors had a hexagonal crystal structure, which was the same as Y2O2S. The emission spectrum and excitation spectrum were measured, and the effect of Sm^3 ＋ molar ratio on the spectra was discussed. The emission spectra of the phosphors showed three emission peaks due to typical transitions of Sm^3 ＋ （4G5/2→6HJ ,J = 5/2, 7/2, 9/2）, and the emission peaks at 606 nm was stronger than others. With the increase of Sm^3 ＋ molar ratio, the emission intensity was strengthened. The excitation peaks were ascribed to the representative energy transition 4f→4f of Ti^4＋ phosphor prepared by co-precipitation method was Sm^3＋ ions. The results indicated that the Y2O2S ： Sm^3＋ , Mg^2＋ , an efficient long afterglow phosphor.     

Synthesis and Upconversion Luminescence of LaF3 ： Yb^3＋ , Er^＋/SiO2 Core/Shell Microcrystals

LaF3：Yb^3＋ , Er^＋ microcrystals were synthesized by a hydrothermal method, and then, the LaF3： Yb^3＋ , Er^＋ microcrystals were coated with silica. Phase identification of LaF3： Yb^3＋ , Er^＋ and LaF3： Yb^3＋ , Er^＋/SiO2 was performed via XRD. The TEM image showed that the size of LaF3： Yb^3＋ , Er^＋ was 150 nm and LaF3： Yb^3＋ , Er^＋/SiO2 presented clearly a core/shell structure with 20 nm shell thickness. The upconversion spectra of LaF3： Yb^3＋ , Er^＋ and LaF3： Yb^3＋ , Er^＋/SiO2 in solid state and in ethanol were studied with a 980 nm diode laser as the excitation source. The upconversion spectra showed that the silica shell had little effect on the properties of fluorescence of the LaF3：Yb^3＋ , Er^＋ microcrystals. At the same time, the green luminescence photo of LaF3： Yb3＋, Er3＋/SiO2 in the PBS buffer was obtained, which indicated that the LaF3： Yb^3＋ , Er^＋/SiO2 could be used in biological applications.     

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 hitrates 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 3μm, 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.     

Preparation of Stable CaS： Eu^2＋ , Tm^3＋ Phosphor

Different fluxes were used to synthesize long persistence phosphors, calcium sulfides activated by Eu^2 and Tm^3 , by convenient solid-state method. The phosphor using NH4F as a flux has good crystallinity and large particle size, its stability against water and other atmospheric components is enhanced, and its afterglow is longer and fluorescent inten-sity is more intense than those of the phosphor using NH4Cl as flux. Their PL intensities varied with time in moist air were measured, no remarkable change was found for those prepared with NH4F flux in contrast with NH4Cl as flux. So using NH4F as flux is a good method to enhance the stability of alkaline earth sulfides.     

Luminescence Properties of Eu~(2 ) and Mn~(2 ) Co-Doped Ca_8Mg(SiO_4)_4Cl_2

The green phosphor for white LED, Ca8Mg(SiO4)4Cl2∶Eu2+, Mn2+, was synthesized by high temperature solid state reaction under reducing atmosphere. During the process of the phosphor prepared, the excess CaCl2 can improve the intensity of emission. The experimental results indicate that there is an effective energy transfer from Eu2+ to Mn2+in Ca8Mg(SiO4)4Cl2 host. This kind of energy transfer may be due to resonance transfer, and this energy transfer is limited.     

Study on Ca8Mg(SiO4)4Cl2:Eu2+ Doped with Sr2+

Ca8Mg(SiO4)4Cl2:Eu2 phosphor doped with Sr2 cation for Ca2 partially, was synthesized by solid-state reaction at high temperature under reducing atmosphere, and its luminescent properties were investigated. The experimental results indicate that the emission intensity of the phosphor increases after being doped with a few amount of Sr2 ion. The emission peak of the phosphor blue shift to about 464 nm when the phosphor is doped with large quantity of Sr2 ions. The excitation spectrum indicates that the phosphor can be well excited by UV and blue light from 300 to 460 nm, and the phosphor was fitted well for the excitation by UV or blue-LED.     

Luminescence and Preparation of LED Phosphor Ca8Mg(SiO4)4Cl2:Eu2+

Calcium magnesium chlorosilicate doped by europium, Ca8Mg(SiO4)4Cl2:Eu2 , was prepared by the solid state reaction at high temperature. The compound obtained is pure Ca8Mg(SiO4)4Cl2 phase with cubic structure. Its average particle size is 5 μm, and it has good dispersity and morphological form. The excitation spectrum of Ca8Mg(SiO4)4Cl2:Eu2 is a wide band, which covers from 270 to 480 nm. The emission spectrum is also a wide band peaked at 510 nm. The luminescent intensity reaches to the maximum when the concentration of Eu2 is 2%. The wavelength of emission and excitation of the phosphor with various Eu2 contents keeps constant. This spectrum range matches violet and blue LED chips very well, and its strong luminescence intensity is suitable for a green phosphor of tricolor phosphor of white light LED.     

Influence of Molten Salt on Luminescent Intensity and Particle Size of Y2O3 ：Eu^3＋ Phosphor

The Y-Eu oxalate precursor was prepared with a homogeneous precipitation method. And the additives, Na2CO3, S, NaCl or their combination, were introduced into the precursor to prepare Y2O3 ：Eu^3＋ red phosphors at 1000 1300 ℃ for 2 h. The effect of molten salts on particle size and luminescent intensity was studied. The experimental results showed that the complex molten salt （Na：CO3 ＋ S ＋ NaCl） was conductive to enhance the luminescent intensity of Y2O3 ：Eu^3＋. The emission intensity of the phosphor prepared with these additives at 1300 ℃ was about 45% higher than that of the one prepared without molten salt, and about 11% higher than that of the corresponding commercial phosphor. Meanwhile, the particle size of Y2O3 ：Eu^3＋ phosphor was controlled effectively with the molten salt.     

Synthesis and luminescence properties of SrAleO4：Eue＋,Dy3＋ hollow microspheres via a solvothermal co-precipitation method

SrAl2O4:Eu2+,Dy3+ hollow microspheres were successfully prepared through a facile and mild solvothermal co-precipitation combining with a postcalcining process.The structure and particle morphology were investigated by X-ray diffraction(XRD),scanning and transmission electron microscopy(SEM and TEM)pictures,respectively.The mechanism for the formation of spherical SrAl2O4:Eu2+,Dy3+ phosphor was preliminary presented.After being irradiated with ultraviolet(UV)light,the spherical phosphor emitted long-lasting green phosphorescence.Both the photoluminescence(PL)spectra and luminance decay,compared with that of commercial bulky powders,revealed that the phosphors had efficient luminescent and long lasting properties.It was considered that the SrAl2O4:Eu2+,Dy3+ hollow microspheres had promising long-lasting phosphorescence with potential scale-dependent applications in photonic devices.     

Photoluminescence Characteristics of Gd2Mo3O9 ： Eu Phosphor Particles by Solid State Reaction Method

Eu^3＋-doped Gd2Mo3O9 was prepared by solid-state reaction method using Na2CO3 as flux and characterized by powder X-ray diffractometry. According to X-ray diffraction, this material belonged to a tetragonal system with space group I41/α. The effects of flux content and sintering temperature on the luminescent properties were investigated with the emission and excitation spectra. The results showed that flux content and sintering temperature had effects on the luminescent properties, the optimized flux content and the best temperature was 3 % and 800 ℃ respectively. The excitation and emission spectra also showed that this phosphor could be effectively excited by C-T band （280 nm）, ultraviolet light 395 nm and blue light 465 nm. The wavelengths at 395 and 465 nm were nicely fitting in with the widely applied output wavelengths of ultraviolet or blue LED chips. Integrated emission intensity of Gd2Mo3O9 ： Eu was twice higher than that of Y2O2S ： Eu^3 ＋ under 395 nm excitation. The Eu^3＋ doped Gd2Mo309 phosphor may be a better candidate in solid-state lighting applications.     

Luminescent Properties of A Novel Terbium Complex Tb（o-BBA）3（phen）

A novel rare earth complex of terbium ion with 2-benzoylbenzoic acid and 1, 10-phenathroline （Tb（o-BBA）3 （phen）, o-BBA-2-benzoylbenzoic acid, phen = 1, 10-phenathroline） was used as an electroluminescent material for the first time. The Tb complex was blended with poly（N-vinylcarbazole） （PVK） in different weight ratios and spinn to coated into films （noted as PVK ：Tb films）. The photoluminescence （PL） properties of films were investigated and the optimum weight ratio between PVK and Tb（o-BBA）3（phen） was found to be 3：1. Monolayer devices with the structure ITO/PVK： Tb/AI were fabricated and emitted green light, which was characteristic of Tb^3＋ emission. The results show that mecha- nisms for PL and EL are different. The PL is considered to be caused because of energy transfer and direct excitation to the Tb（o-BBA）3（phen） molecule, while EL is mainly on charging trapping.     

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…