Synthesis and Luminescence Improvement of CaAlSiN_(3) Phosphors Doped with Eu^(2+) and Mn^(2+) for White LEDs

Eu^(2+) and Mn^(2+) co-activated CaAlSiN_(3) red phosphors were produced using the solid-state reaction tech⁃nique in a N2 environment.Excitation spectra,emission spectra,and diffuse reflection spectra were used to study the luminescence characteristics,energy gap,and thermal stability in detail.CaAlSiN_(3)∶Eu^(2+) exhibits an extended emission band when stimulated with 450 nm blue light,which is caused by the 4f65d to 4f7 transition of Eu^(2+).Similar⁃ly,CaAlSiN_(3)∶Mn^(2+) displays a wide emission band centered at 628 nm,which results from Mn^(2+)’s transition from 4T1(4G) to 6A1(6S).When the ions of Mn^(2+)were combined into CaAlSiN_(3)∶Eu^(2+),the photoluminescence intensity of Eu^(2+ )was greatly boosted because there was energy transfer and co-emission between Mn^(2+) and Eu^(2+).Beyond that,CaAlSiN_(3)∶Eu^(2+),Mn^(2+) emerges with splendid thermostability and high quantum efficiency,the quenching temperature surpasses 300℃,and the internal quantum efficiency is determined to be around 84.9%.The white LED was pack⁃aged with a combination of CaAlSiN_(3)∶Eu^(2+),Mn^(2+),LuAG∶Ce3+ and a blue chip.At a warm white-light corresponding color temperature(3009 K) with CIE coordinates(0.4223,0.3748),the color rendering index Ra has reached 93.2.CaAlSiN_(3)∶Eu^(2+),Mn^(2+) would have great application potential as a red-emitting phosphor for white LEDs.

Preparation and characterization of Eu^(3+)-doped CaCO_3 phosphor by microwave synthesis

A Eu^3＋-doped CaCO3 phosphor with red emission was prepared by microwave synthesis. The scanning electron microscopy （SEM） image and laser particle size analysis show that the CaCO3：Eu^3＋ particles are needle-like in the length range of 5.0-10.0 μm. The results of X-ray diffraction （XRD） analysis, Fourier transform infrared spectroscopy （FT-IR）, and Raman spectroscopy indicate that pure aragonite CaCO3：Eu^3＋ is prepared using microwave irradiation and the Eu^3＋ ion as a luminescence center inhabits the site of Ca^2＋. The photoluminescence excitation （PLE） spectrum shows that the strong broad band at around 270 nm and weak sharp lines in 300-550 nm are assigned to the charge transfer band of Eu^3＋-O^2- and intra-configurational 4f-4f transitions of Eu^3＋, respectively. The photoluminescence （PL） spectrum implies that the red luminescence can be attributed to the transitions from the ^5D0 excited level to the ^7FJ （J = 0, 1, 2, 3, 4） levels of Eu^3＋ ions with the mainly electric dipole transition ^5D0 → ^7F2 （614 and 620 nm）, and the Eu^3＋ ions prefer to occupy the low symmetric site in the crystal lattice.

Structure and Luminescence Properties of Eu^(3+) Doped SiO_2 Glass Synthesized by Sol-Gel Process

Under different annealing temperatures, Eu 3+ doped SiO 2 gel and glass were prepared by sol gel method, and the structure and luminescent properties were studied with excitation spectra, emission spectra, IR and DTA TG. The results show that the fluorescent intensity tends to get stable when concentration of Eu 3+ doped is above 1 86 % (mass fraction) most water absorbed by the gel was removed at 300 ℃, and that the emission spectrum of Eu 3+ , with peaks at 614, 588, 577 nm, is due to 5D 0→ 7F 2, 5D 0→ 7F 1, 5D 0→ 7F 0 transitions, and the excitation peaks at 318, 362, 380, 393, 412 and 462 nm were observed. These results illustrate that the temperature range of 300～500 ℃ is critical for the structure conversion from gel to glass, and the fluorescence is strongly quenched by water.

Annealing Temperature-Dependent Luminescence Color Coordination in Eu-Doped AlN Thin Films

AlN was used as a host material and doped with Eu grown on Si substrate by pulsed laser deposition (PLD) with low substrate temperature. The X-ray diffraction (XRD) data revealed the orientation and the composition of the thin film. The surface morphology was studied by scanning electron microscope (SEM). While raising the annealing temperatures from 300˚C to 900˚C, the emission was observed from AlN: Eu under excitation of 260 nm excitation. The photoluminescence (PL) was integrated over the visible light wavelength shifted from the blue to the red zone in the CIE 1931 chromaticity coordinates. The luminescence color coordination of AlN: Eu depending on the annealing temperatures guides the further study of Eu-doped nitrides manufacturing on white light emitting diode (LED) and full color LED devices.

Interpretation of the 4f-5d Excitation Spectra of Eu^(3+) and Tb^(3+) Doped in Crystals

The structure of the low-temperature 4f^N→4f^N-15d excitation spectra of Eu^3＋ and Tb^3＋ doped in crystals LiYF4, YPO4 and CaF2 measured by van Pieterson et al. in 2002 was analyzed and assigned based on the simple model proposed by Duan and co-workers in the last few years. Some complemental discussion on effects of J-mixing on the f-d transition intensities for Eu^3＋ due to the f-electron crystal-field interaction Hcf（f）, which was ignored in the simple mod- el, was presented. Some previously unexplained peaks for Tb^3 ＋ were interpreted to be spin-forbidden transitions to higher 5d crystal-field levels, or assigned to be f→d excitations with the core 4f7 excited from ^8S to ^6P, ^6I and ^6D, respectively. It is shown that the main structure of 4f-Sd excitation spectra of Eu^3＋ and Tb^3＋ can be well interpreted with the simple model.

Influence of annealing temperature on luminescent properties of Eu^(3+)/V^(5+) co-doped nanocrystalline Gd_2Ti_2O_7 powders

Nanosized Gd2(1–x)Eu2xTi2O7:yV5+ phosphors were prepared via sol-gel method and characterized with X-ray diffraction,Raman spectroscopy,diffuse reflectance spectra and photoluminescence spectra.Their PL properties were investigated as functions of the Eu3+ doping concentration and annealing temperature.The results indicated that the as-prepared samples showed a strong emission of Eu3+ under the irradiation of 303 nm.For Eu3+-doped Gd2Ti2O7,the orange emission at 586 nm was the strongest,which was correspond...

Effects of Heat-treatment Temperature on Eu^(3+) and Li^+ Co-doped ZnO Photoluminescence by Sol-gel Process

The photoluminescence （PL） characteristics of Eu^3＋ and Li^＋ co-doped ZnO PL materials against heat-treatment temperature were discussed. The PL xerogel and powder samples were prepared by solgel process. The emission spectra of all samples showed two broad bands peaking at 590 nm and 620 nm under UV-Vis excitation. But the relative intensity of red PL （620 nm） was much greater than that of green PL （590 nm） of the same sample, that s to say, the red color was the main luminescence. With heat-treatment temperature increase, the two kinds of colors PL intensity decreased, and both the red and green PL intensity of the xerogel samples was much greater than those of powder samples respectively. The XRD patterns revealed that Eu^3＋ ions were successfully incorporated in ZnO crystals in xerogel samples. When heat-treatment temperature reached 350 ℃, the Eu^3＋ began to separate out of the ZnO crystals and Eu2O3 crystals came into being. When the powder sample was subjected to UV-Vis excitation, the energy transfered from the host ZnO emission to Eu^3＋ became weaker than the xerogel sample.

Effect of co-doped metal caions on the properties of Y_2O_3:Eu^(3+) phosphors synthesized by gel-combustion method

Y2O3：Eu3＋ phosphors co-doped with different metal cations （Li＋, Na＋, K＋, Mg2＋, Ca2＋） are prepared by the gel- combustion method with Y2O3：Eu3＋, and R（NO3）x （R = Li, Na, K, Mg, Ca） serving as raw materials and glycine as fuel, calcined at 1000 ℃ for 2 h. The synthesized Y203 ：Eu3＋ phosphors doped with different metal cations and doping ratios are characterized by x-ray diffractometry （XRD）, fluorescence and phosphorescent spectrophotometer. The co-doping metal cations are advantageous to the development of Y203：Eu3＋ lattice. All the samples can emit red light peaked at 611 nm under 254-nm excited. The luminescence intensities of co-doping samples are increased because the cations increase the electron transition probability of Eu3＋ from 5D0 level to 7F level. The fluorescence lifetime of Eu3＋ （SD0 --＋7F2） is increased by doping metal cations.

Long Lasting Phosphorescence in Eu^(2+) and Ce^(3+) Co-Doped Strontium Borate Glasses

Long lasting phosphorescence (LLP) was observed in Eu2+, Ce3+ co-doped strontium borate glasses prepared under the reducing atmosphere due to the emission of both Eu2 + and Ce3+ . The methods of photoluminescence, thermolu-minescence and phosphorescence were used to study the samples, and possible mechanism was suggested. The co-doping of Ce3 + ions poisoned the phosphorescence emission of Eu2 + because of the competition to obtain the trapped electron . The phosphorescence of Ce3 + in the sample decays more quickly than that of Eu2 + , which is suggested for the reason that the emission energy of Ce3 + is higher or the distance between Ce3 + and electron traps of the glasses is longer.

Luminescence properties of YAl_3(BO_3)_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%.

Extended X-ray Absorption Fine Structure Study of Eu-Doped BaPbO_3

The neighbor structure of Pb and Eu atoms in the Eu doped BaPbO 3 polycrystal powder has been studied with the extended X ray absorption fine structure(EXAFS). Mean distances of Pb O and Eu O are obtained. Furthermore by means of XRD and ICP analysis, it is proved that Eu 3+ partially replaces Pb 4+ and results in the formation of oxygen vacancies in the system of Eu doped BaPbO 3.

Effect of Al^3＋ on Photoluminescence Properties of Eu^3＋-Doped BaZr（BO3）2 Phosphors

We discuss the influence of Al^3＋ on the charge transfer state （CTS） and the photoluminescence properties of BaZr（BO3）2：Eu. The results reveal that there is a red shift which is about 20nm for the charge transfer state when doping with Al^3＋ and indicate the formation of ‘free＇ electrons due to the change of microstructures. In addition, the influence or Al^3＋ doping on the PPR is analysed and a new explanation is raised based on the photo luminescent mechanism. It is the CTS intensity rather than the CTS energy that influences the peak-peak ratio.

Improving luminescent property of SrIn_2 O_4 :Eu^(3+) by co-doped A^+ (A = Li, Na, K) or Sm^(3+)

A series of SrIn2 O4 ：Eu^3＋ phosphors are synthesized by a high temperature solid-state method, and their luminescent properties are investigated. They can be excited by 395-nm radiation, and produce red emission （619 nm）; however, they have a low absorption of near-ultraviolet light with the wavelength of 400nm–405 nm. When co-doped with A^＋ （A=Li, Na, K）, the emission intensity of SrIn2O4 ：Eu^3＋ is significantly enhanced, but its emission and excitation spectral profile is unchanged. With co-doping Sm^3＋ , not only is the emission intensity of SrIn2 O4 ：Eu^3＋ enhanced, but also the absorption is broadened and strengthened in the range of 400 nm–405nm. The effect of Sm^3＋ -doped content on the emission intensity of SrIn2O4 ：Eu^3＋ , Sm^3＋ is investigated, and the optimal Sm^3＋ content is 0.02 mol.

Photoluminescence of BaGdB_9O_(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-→Eu^3＋.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-→Gd^3＋.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 Eu^3＋.When excited with 254 nm, the integral emission intensity of Eu^3＋ increased after Al^3＋ or Sc^3＋ substituting Gd^3＋ partly in BaGd0.9Eu0.1B9O16.Under 147 nm excitation, the integral emission intensity of Eu^3＋ decreased after some Gd^3＋ was replaced by Sc^3＋, but increased after adding appropriate Al^3＋ into BaGd0.9Eu0.1B9O16.

Enhanced Emission of Eu^(3+) in Boron Ions-Doped Sol-Gel SiO_2 Phosphors

Al-doped and B, Al-codoped silica xerogel was fabricated by sol-gel process. The influence of B ions and annealing temperature on luminescent properties of phosphors were studied by using fluorescence spectrum, X-ray diffraction, DSC, TG/DTG analysis and IR spectrum. The heat treatment has a large effect on the luminescent properties. Under 248 nm excitation, the emission spectrum of samples heated shows characteristic emission peaks of Eu^3＋ ions are, which are due to the transitions of ^5D0→^7FJ（J = 0, 1, 2, 3, 4） of Eu^3＋ , respectively. The transition of ^5D0→^7F1 is split into two peaks.

Site Selective Spectra of Eu^(3+)-Doped Y_2SiO_5 Crystal

By using a whitelight lamp, an Ar+ ion laser whosewavelength was tuned to 457. 9 nmand a tunable Rh 6G dye laser(linewidth: 0. 5 cm-1) pumped bythe second harmonic of a Nd: YAGlaser as light sources and using amonochromator, a phase-lockingamplifier and a computer as the data detecting system, the transmission spectrum, fluorescence spectra, excitation spectrum and siteselective fluorescence spectra ofthe Eu3+: Y2SiO5 crystal were observed. More than thirty out of thetotal fifty spectral lines were observed for 5D0→7F0,1,2,3,4 transitions. The Eu3+ ions occupy twokinds of the Y3+ sites with the lowsymmetry in this crystal. The difference of the wavelengths of thetwo Eu3+ sites for 7F0→5D0 transition is about 0. 2 nm. It was foundthat the two sites were nonequivalent optical ones at room temperature. Crystal lattice constants a,b, c, and β of Eu3+: Y2SiO5 werealso measured by the X-ray diffraction method. The results show thatthe lattice constants a, b, and cof the crystal doped Eu3+ ions isvery close to those of the Y2SiO5crystal undoped Eu3+ ions.

Persistent Spectral Hole Burning of Eu^3＋ Doped Y2SiO5 Crystal at 579.62 nm

By using an Ar^＋ ion laser, a tunable Rh6G dye laser（linewidth： 0.5 cm^-1） pumped by the second harmonic of a YAG：Nd laser and an 899-21 dye laser as light sources and using a monochromator, a phase-locking amplifier and a computer as the data detecting system, the spectra and spectral hole burning of Eu^3＋：Y2SiO5 crystal were researched in this paper.Photoluminescence excitation spectrum and site selective fluorescence spectrum were detected at room temperature and 77 K. Hole burning experiments were reached at 16 K. A spectral hole with hole width of about 80 MHz were detected and it could be kept for 10 h.

Spectral Properties and Sensitization of Ce^(3+) and Eu^(2+) Codoped Calcium Zinc Chlorosilicate

The Ce^3+ and Eu^2+ ions codoped calcium zinc chlorosilicate Ca_8Zn(SiO_4)_4Cl_2 phosphors have been synthesized for the first time. The diffuse reflection, excitation and emission spectra of Ca_8Zn(SiO_4)_4Cl_2∶Ce^3+, Eu^2+ have been measured at room temperature. The luminescence sensitizaiton of Eu^2+ by Ce^3+ inCa_8Zn(SiO_4)_4Cl_2∶Ce^3+, Eu^2+ has been expounded under the excitation of ultraviolet light and the efficient nonradiative energy transfer from Ce^3+ to Eu^2+ in this system is confirmed.

Quenching Study on Iron Impurity in Eu^(2+), Dy^(3+) Doped Strontium Aluminate Phosphor Prepared by Nano-Coating Process

A series of long afterglow phosphors, Eu2+, Dy3+, with different iron content were prepared by nano-coating process. The resulted precursors were characterized by Transmission Electron Microscope (TEM), which suggested that the precursor particles had nanometer size distribution. The optical quenching of iron impurity on the phosphor powders were investigated by X-Ray powder Diffraction (XRD) and photoluminescence methods. The XRD indicates that a pure monoclinic SrAl2O4∶Eu2+, Dy3+ was formed at 1200 ℃ and iron impurity up to 296.36×10-4% had no effect on the SrAl2O4∶Eu2+, Dy3+ phase structure. However, the luminescence intensity were strongly dependent on the trace iron impurity, which might be explained that iron displace the aluminium and form Fe-O bond, which competed energy with Eu2+ and transfer red them to infrared sites.

红色荧光粉CaAlSiN_(3)∶Eu^(2+)的结构精修和性能

运用高温固相法合成系列掺铕(Eu)的氮化物荧光粉Ca1-xAlSiN_(3)∶xEu^(2+),对所得到的最佳样品Ca_(0.99)AlSiN_(3)∶0.01Eu^(2+)进行系列表征和结构精修.结果表明,样品Ca_(0.99)AlSiN_(3)∶0.01Eu^(2+)的晶粒尺寸为10μm左右,各元素分布均匀,其精修图与实测XRD谱图基本吻合,属于正交晶系结构.该样品的色坐标为(0.645 1, 0.354 5),落在红光区域,色纯度高达100%,相关色温为2 449 K,属于低色温.该荧光粉在298~473 K范围内表现出良好的热稳定性,活化能为0.26 eV,具有广阔的市场前景.