Study on Effect of Flux on CeMgAl11O19∶Tb3+ Phosphor

High calcination temperature is an important factor in the preparation process of CeMgAl11O19∶Tb3 . To decrease the temperature, different fluxes(H3BO3, MgF2 and AlF3) were tested in order to compare their influence on the luminescence property and particle size distribution of CeMgAl11O19∶Tb3 . The result shows that when the content of MgF2 is 0.1 mol/mol, the intensity of luminescence can attain a maximum. Furthermore, MgF2 can improve the particle size quality of the phosphor. So MgF2 can take the place of the conventional flux H3BO3 to prepare high quality CeMgAl11O19∶Tb3 phosphor. In addition, the relation between phosphor property and content of AlF3 was also studied. The crystal structure of the phosphor was analyzed by XRD method. The phase composition analysis shows that the reason of decrease of the brightness of CeMgAl11O19∶Tb3 phosphor is the emergence of TbAlO3 and α-Al2O3 during the preparation process.     

Preparation of Stable CaS∶Eu~(2+), Tm~(3+) Phosphor

Alkalineearthsulfides (AES)havebeenfoundtobeexcellentandversatilephosphor ,andrareearthsasactivatorshavebeenintensivelyinvestigated[1～ 7] .Theyholdpromiseforapplicationsinphoto ,electro ,cathoderay ,fieldemissiondisplaysandluminescencepaints[8,9] .However ,alkalineearthsulfidesasaphos phorhosthavebeenfoundtobelimitedinapplica tion ,duemainlytoitssensitivetomoistureandotheratmosphericcomponents .Theirchemicalstabilityagainstatmosphericcarbondioxideandmoisturecouldbeenhancedthroughthegoodcryst…     

Sol-Gel Preparation of Zn2 SiO4 :Mn Phosphor Layers on Silica Spheres and Their Luminescent Properties

The synthesis and luminescence properties of Zn2 SiO4: Mn phosphor layers on spherical silica spheres, i.e.,a kind of core-shell complex phosphor, Zn2SiO4: Mn@ SiO2 were described.Firstly, monodisperse silica spheres were obtained via the Stober method by the hydrolysis of tetraethoxysilane(TEOS) Si ( OC2H5 ) 4 under base condition ( using NH4 OH as the catalyst).Secondly, the silica spheres were coated with a Zn2 SiO4: Mn phosphor layer by a Pechini solgel process.X-ray diffraction ( XRD), scanning electron microscope ( SEM), energy-dispersive X-ray spectrum ( EDS )and photoluminescence (PL) were employed to characterize the resulting complex phosphor.The results confirm that1000 ℃ annealed sample consists of crystalline Zn2SiO4: Mn shells and amorphous SiO2 cores.The phosphor show the green emission of Mn2 at 521 nm corresponding 4T1 (4G) - 6 A1 (6S) transition, and the possible luminescence mechanism is proposed.     

Study on Effect of Flux on CeMgAl_(11)O_(19)∶Tb ~(3 ) Phosphor

Asthebackgroundlightofhighqualityliquidcrystaldisplay (LCD) ,coldcathodefluorescentlamp(CCFL)becametheresearchemphasisalongwiththedevelopmentofthemarketofLCD .AnimportantissueagainsttheapplicationofCCFListhebrightnessandlifetimeofthephosphors .CeMgAl11O19∶Tb3 (CMAT)isaveryimportantgreen emittingphosphorfortheim provementofbrightnessofCCFL .CeMgAl11O19∶Tb3 isakindofhexagonalpoly aluminatewiththestructureasshowninFig .1.Thecrystalstructureissimilartomagnetoplumbite (idealformula…     

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 nitrates 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 3 μm, 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.     

Low Temperature Luminescence Properties of Tm3+ Doped Aluminate Phosphor

(Ba0.66Sr0.33)Mg0.8Al11.47O19:Tm0.013 (BSMA:Tm3 ) phosphor was synthesized by solid-state reactions. The sample was characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), vacuum ultraviolet (VUV) spectra, ultraviolet (UV) spectra and FT-IR spectrum. XRD pattern reveals that BSMA:Tm3 has the same structure as BaAl12O19 phase. SEM image illustrates that the phosphor has the hexagonal shape and deep slice structure. VUV and UV emission spectra at 20, 50 and 100 K show that the low temperature luminescence intensities become weak gradually with the increasing of the temperature under 147 and 254 nm excitation. The strong broadband peaks at around 357 and 397 nm and the peak at 516 nm under 147 nm excitation all correspond to the characteristic transitions of Tm3 ions. However, under UV (254 nm) excitation, the main peak becomes 530 nm which has very high line intensity, and the peaks at about 362 and 403 nm are very weak. The excitation spectrum at 20 K shows that there are three absorption peaks at around 153, 186 and 193 nm when 516 nm emission is monitored. The absorption peaks of [AlO4], [AlO6] and Al-O can be observed in FT-IR spectrum.     

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.     

New red phosphor （Y, Gd, Lu）BO3： Eu^3＋ for PDP applications

Highly efficient phosphors under vacuum ultraviolet excitation are still demanded for the development of plasma display panels and Hg-free fluorescent lamps. The phosphors of Eu3+ doped (Y, Gd, Lu)BO3 were synthesized with solid state reaction method and the con-tents of Y3+, Gd3+, and Lu3+ for plasma display panel red phosphor were optimized under vacuum ultraviolet excitation. Two new potential candidates, which were (Y1-S-7TGdSLuT)BO3: Eu3+ (0相似文献   

Modification of Luminescent Properties of Red Sulphide Phosphors for White LED Lighting

A kind of sulphide, CaS:Eu2 , activated by europium ion for white LED lighting was synthesized via solid-state reaction route in reducing atmospheres. The phosphors were then encapsulated with silicone resin. Moreover, chemical structure of the phosphors was characterized by XRD. Microstructure of the powders was observed by SEM. Spectra of excitation and emission for the phosphors were also obtained by a spectrophotometer. Effect of processing parameters on the luminescent properties of the powders was systematically studied to result in the phosphors with good chemical stability and maximal relative luminescent intensity.     

Sol-Gel Synthesis and Luminescent Characteristic of Doped Eu^3 ＋ Silicate-Silica Phosphor

Silicagelphosphorsdopedrareearthionshave attractedgreatattentionofmanyresearchersdueto theseadvantages,suchashighersamplehomogeneity,purityandstable,efficientandenvironmentallyfriend lyphotoluminescencematrixmaterials,whichisless toxicleadtonetconversione…     

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.     

Luminescence Properties of Green-Emitting Phosphor (Ba1-x,Srx)2SiO4:Eu2+ for White LEDS

The (Ba1-xSrx)2SiO4∶Eu2 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 4f65d1→4f7 transition of the Eu2 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-xSrx)2SiO4∶Eu2 is a promising phosphor for green white-lighting-emission diode by ultraviolet chip.     

Preparation,Structural Analysis and Luminescence Properties of Nanocrystalline Phosphor Gd2O3∶Eu

Nanocrystalline monoclinic and cubic Gd2O3∶Eu with different Eu3 concentration were prepared using glycine-nitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, pure monoclinic and cubic Gd2O3∶Eu with particle size less than 40 nm can be easily formed. Under ultraviolet excitation, main emission of Eu3 (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 Gd3 and Eu3 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.     

Luminescent Properties of Green Phosphor Ca8Mg（SiO4 ）4 Cl2：EU^2＋ , DY^3＋ for LED Applications

The new phosphor calcium magnesium chlorosilicate, codoped with Eu^2＋ and Dy^3＋, was synthesized with the help of the high temperature solid state reaction in reducing atmosphere. The excitation and emission spectra were very similar to that of Ca8Mg（SiO4）4Cl2 ：Eu^2＋, and the Dy^3＋ concentration influenced the emission intensity of this phosphor. The intensity of Eu^2＋ and Dy^3＋ codoped CMSC was stronger than that of Eu^2＋ singly doped CMSC. The emission spectrum of the Dy^3＋ ion overlapped the absorption band of the Eu^2＋ ion, indicating that an energy transfer from Dy^3＋ to Eu^2＋ took place in CMSC：Eu^2＋, Dy^3＋ phosphor. The mechanism of the energy transfer from Dy^3＋ tO Eu^2＋, in this phosphor, might be resonant energy transfer.     

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.     

Synthesis and Properties of Eu Activated Strontium Molybdate Phosphor

In order to prepare fluorescent material for white Light Emitting Diodes （LEDs）, a new Eu^3＋ activated molybdate phosphor SrMoO4 was fabricated with solid-state method. X-ray diffraction （XRD） showed that the doping of trivalent europium ion reduced the lattice parameters. The excitation and emission spectra indicated that this phosphor could be excited effectively by the visible light, and then emitted red light with the peaks located at 616 and 624 nm. The influence of Eu^3＋ concentration on the luminescent properties of Eu^3＋ doped SrMoO4 was investigated and the 25% （mole fraction） was the appropriate molar concentration. The reaction time and temperature had obvious effect on the luminescent properties. The luminescent intensity reached the strongest when it was sintered at 800 ℃ for 3 h.     

Citric Gel Synthesis and Luminescent Properties of Ce^3＋-Activated SrGa2O4 Phosphor

Ce^3＋-activated SrGa2O4 phosphor was synthesized by a method of citric gel,wherein citric acid served as a chelate agent,and the as-synthesized powder was calcined in a slightly reduced ambient.The crystallization characteristics of the sample varied with the calcining temperature.Compared with the phosphor prepared by the solid-state reaction,the phosphor synthesized by citric gel was calcined at a relatively lower temperature.Consequently,the volatilization of Ga2O3 during high-temperature calcining process was avoided.The typical double-peak emission of Ce^3＋ originated from 2D（5d）→4F5/2（4f）,and 2D（5d）→4F7/2（4f）was observed,and the intrinsic emission of SrGa2O4 host was much restricted.The emission intensity varied with the calcining temperature because the different crystallinity and the optimal concentration of Ce-dopant was determined at 3%.     

Effect of Organic Solvent and Resin on Luminescent Capability of SrAl2O4:Eu2+, Dy3+ Phosphor

Organic substance such as solvent and resin's effect on luminescent capability of SrAl2O4:Eu2 , Dy3 phosphor was studied. Some organic solvents and resins were selected for experimentation. The results indicate that those organic solvents will not have negative effect on the applied capability of SrAl2O4:Eu2 , Dy3 phosphor. Adopting the organic resins and covering method, the afterglow luminance of SrAl2O4:Eu2 , Dy3 phosphor was increased by 85.01% and 82.51%.