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1.
Structural, morphological and optical properties of rare earth ions (RE3+=Sm3+ or Dy3+) activated Ca3Ga2Si3O12 (CaGaSi) phosphors synthesized by the sol-gel method are reported. XRD results confirmed the cubic phase structure of RE3+:CaGaSi phosphors. From the SEM images of RE3+:CaGaSi phosphors, it is observed that the particles are agglomerated. Photoluminescence spectra of Sm3+:CaGaSi phosphors have shown bright orange red emission at 598 nm (4G5/2→6H7/2) with an excitation wavelength of λexci=401 nm. In the case of Dy3+:CaGaSi phosphors bright yellow emission has been observed at 574 nm (4F9/2→ 6H13/2) with λexci=451 nm. From the PL spectral results, the rare earth ion concentration of CaGaSi phosphors is optimized. 相似文献
2.
Xin-Yuan Sun Jun-Cheng ZhangXin-Gen Liu Liang-Wu Lin 《Physica B: Condensed Matter》2011,406(21):4089-4093
The Ca2.95−yDy0.05B2O6:yNa+ (0≤y≤0.20) phosphors were synthesized at 1100 °C in air by the solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE), photoluminescence (PL) spectra and thermoluminescence (TL) spectra. The PLE spectra show the excitation peaks from 300 to 400 nm due to the 4f-4f transitions of Dy3+. This mercury-free excitation is useful for solid-state lighting and light-emitting diodes (LEDs). The emission of Dy3+ ions on 350 nm excitation was observed at 480 nm (blue) due to the 4F9/2→6H15/2 transitions, 575 nm (yellow) due to 4F9/2→6H13/2 transitions and 660 nm (red) due to weak 4F9/2→6H11/2 emissions. The PL results from the investigated Ca2.95−yDy0.05B2O6:yNa+ phosphors show that Dy3+ emissions increase with the increase of the Na+ codoping ions. The integral intensity of yellow to blue (Y/B) can be tuned by controlling Na+ content. By the simulation of white light, the optimal CIE value (0.328, 0.334) can be achieved when the content of Na+-codoping ions is y=0.2. The results imply that the Ca2.95−yDy0.05B2O6:yNa+ phosphors could be potentially used as white LEDs. 相似文献
3.
Trivalent dysprosium ions (Dy3+) doped strontium molybdate (SrMoO4) phosphors were synthesized by solid-state reaction and their photoluminescence (PL) properties were investigated. X-ray powder diffraction (XRD) analysis confirmed the formation of SrMoO4:Dy3+. PL measurements indicated that the phosphor exhibited intense emission at 482, 490 (4F9/2→6H15/2) and 575 nm (4F9/2→6H13/2) under UV excitation. The effect of the doping concentration of Dy3+in SrMoO4:Dy3+ on the PL was investigated in detail. Na+ ion was a good charge compensator for SrMoO4:Dy3+. 相似文献
4.
The spectroscopic properties in UV-excitable range for the phosphors of Sr3La2(BO3)4:RE3+ (RE3+=Eu3+, Ce3+, Tb3+) were investigated. The phosphors were synthesized by conventional solid-state reactions. The photoluminescence (PL) spectra and commission international de I'Eclairage (CIE) coordinates of Sr3La2(BO3)4:RE3+ were investigated. The f-d transitions of Eu3+, Ce3+ and Tb3+ in the host lattices are assumed and corroborated. The PL and PL excitation (PLE) spectra indicate that the main emission wavelength of Sr3La2(BO3)4:Eu3+ is 611 nm, and Sr3La2(BO3)4:Ce3+ shows dominating emission peak at 425 nm, while Sr3La2(BO3)4:Tb3+ displays green emission at 487, 542, 582 and 620 nm. These phosphors were prepared by simple solid-state reaction at 1000 °C. There are lower reactive temperature and more convenient than commercial phosphors. The Sr3La2(BO3)4:Tb3+ applied to cold cathode fluorescent lamp was found to emit green light and have a major peak wavelength at around 542 nm. These phosphors may provide a new kind of luminescent materials under ultraviolet excitation. 相似文献
5.
In the present paper, phosphors with the composition Y3−x−yAl5O12:Bi3+x, Dy3+y were synthesized with solid state reactions. The luminescence properties of Bi3+ and Dy3+ in Y3Al5O12(YAG) and the energy transfer from Bi3+ to Dy3+ were investigated in detail. Bi3+ in YAG emits one broad band peaking at 304 nm which can be ascribed to the transition from excited states 3P0, 1 to ground state 1S0. Dy3+ in YAG emits two groups of peaks around 484 and 583 nm, respectively, which can be ascribed to the transitions from excited state 4F9/2 to ground states 6H15/2 and 6H13/2. The co-doping of Bi3+ enhances the luminescent intensity of Dy3+ by ∼7 times because Bi3+ can transfer the absorbed energy to Dy3+ efficiently. The mechanism of energy transfer was also discussed. 相似文献
6.
K.D OskamK.A Kaspers A Meijerink H Müller-BunzTh Schleid 《Journal of luminescence》2002,99(2):101-105
The luminescence properties of Ce3+ in La3F3[Si3O9] are reported. Excitation and emission bands corresponding to 4f1→5d1 transitions of Ce3+ were identified. The center of gravity of the 5d states lies at remarkable high energy (43.2×103 cm−1) for Ce3+ in a silicate compound. This high value is attributed to the combined oxygen/fluoride coordination of the Ce3+ ion. Emission from the lowest 4f5d level to the 2F5/2 and 2F7/2 levels was found at 32.4×103 and 30.4×103 cm−1. These results are compared with literature data on silicates and fluorides. From the values found for Ce3+, predictions are made for the positions of the 4f5d bands of Pr3+ and Er3+ in La3F3[Si3O9]. For both ions, it is concluded that in this host lattice emission is expected from high lying 4fn energy levels. 相似文献
7.
This report presents the luminescence properties of Ce3+ and Pr3+ activated Sr2Mg(BO3)2 under VUV-UV and X-ray excitation. The five excitation bands of crystal field split 5d states are observed at about 46 729, 44 643, 41 667, 38 314 and 29 762 cm−1 (i.e. 214, 224, 240, 261 and 336 nm) for Ce3+ in the host lattice. The doublet Ce3+ 5d→4f emission bands were found at about 25 840 and 24 096 cm−1 (387 and 415 nm). The influence of doping concentration and temperature on the emission characteristics and the decay time of Ce3+ in Sr2Mg(BO3)2 were investigated. For Pr3+ doped samples, the lowest 5d excitation band was observed at about 42017 cm−1 (238 nm), a dominant band at around 35714 cm−1 (280 nm) and two shoulder bands were seen in the emission spectra. The excitation and emission spectra of Ce3+ and Pr3+ were compared and discussed. The X-ray excited luminescence studies show that the light yields are ∼3200±230 and ∼1400±100 photons/MeV of absorbed X-ray energy for the samples Sr1.86Ce0.07Na0.07Mg(BO3)2 and Sr1.82Pr0.09Na0.09Mg(BO3)2 at RT, respectively. 相似文献
8.
The Sm3+-doped CaWO4 nanoparticles were synthesized by hydrothermal method. The room temperature photoluminescence (PL) spectra of Sm3+-doped CaWO4 nanoparticles doped with different Sm3+ concentrations under 405 nm excitation have been investigated. The PL spectra showed four strong emission peaks at 460, 571, 609, and 653 nm. The first emission peak at 460 nm could be due to a structural defect of the lattice, an oxygen-deficient WO3 complex. The other three emissions at 571, 609, and 653 nm were due to the f-f forbidden transitions of the 4f electrons of Sm3+, corresponding to 4G5/2→6H5/2 (571 nm), 6H7/2 (609 nm), and 6H9/2 (653 nm), respectively. In addition, the optimum Sm3+ concentration in CaWO4 nanoparticles for optical emission was determined to be 1.0%. The Sm3+4G5/2→6H7/2 (609 nm) emission intensity of Sm3+-doped CaWO4 nanoparticles significantly increased with the increase of Sm3+ concentration, and showed a maximum when Sm3+ doping content was 1.0%. If Sm3+ concentration continued to increase, namely more than 1.0%, the Sm3+4G5/2→6H7/2 emission intensity would decrease. The present materials might be a promising phosphor for white-light LED applications. 相似文献
9.
In this paper we report the combustion synthesis of trivalent rare-earth (RE3+ = Dy, Eu and Ce) activated Sr4Al2O7 phosphor. The prepared phosphors were characterized by the X-ray powder diffraction (XRD) and photoluminescence (PL) techniques. Photoluminescence emission peaks of Sr4Al2O7:Dy3+ phosphor at 474 nm and 578 nm in the blue and yellow region of the spectrum. The prepared Eu3+ doped phosphors were excited by 395 nm then we found that the characteristics emission of europium ions at 615 nm (5D0?7F2) and 592 nm (5D0?7F1). Photoluminescence (PL) peaks situated at wavelengths of 363 and 378 nm in the UV region under excitation at around 326 nm in the Sr4Al2O7:Ce3+ phosphor. 相似文献
10.
LiCaBO3:M (M=Eu3+, Sm3+, Tb3+, Ce3+, Dy3+) phosphors were synthesized by a normal solid-state reaction using CaCO3, H3BO3, Li2CO3, Na2CO3, K2CO3, Eu2O3, Sm2O3, Tb4O7, CeO2 and Dy2O3 as starting materials. The emission and excitation spectra were measured by a SHIMADZU RF-540 UV spectrophotometer. And the results show that these phosphors can be excited effectively by near-ultraviolet light-emitting diodes (UVLED), and emit red, green and blue light. Consequently, these phosphors are promising phosphors for white light-emitting diodes (LEDs). Under the condition of doping charge compensation Li+, Na+ and K+, the luminescence intensities of these phosphors were increased. 相似文献
11.
S. SailajaS.J. Dhoble C. Nageswara RajuB. Sudhakar Reddy 《Physica B: Condensed Matter》2012,407(1):103-107
5 mol% of Pr3+ and Tm3+ ions activated calcium gadolinium tungstate (Ca2Gd2W3O14) phosphors were synthesized by traditional solid state reaction method. Crystalline phase structure was identified from the X-ray diffraction (XRD) profiles. From the scanning electron microscopy (SEM) images, we have observed the agglomeration of the particles, and average grain size is around 40-300 nm. Using the energy dispersive X-ray analysis (EDAX) and Fourier transform infrared (FTIR) spectra, identified the elements and functional groups present in the prepared phosphors. The emission spectrum of Pr3+: Ca2Gd2W3O14 powder phosphors have shown an intense red emission at 615 nm with the excitation wavelength λexci=450 nm and thus these red color emitting powder phosphors are used as one of the components in the preparation of WLEDs. The excitation spectrum of Tm3+: Ca2Gd2W3O14 powder phosphor has shown a ligand to metal charge transfer (W-O) band (LMCT) within the WO42− group. Emission spectrum of Tm3+: Ca2Gd2W3O14 phosphors have shown blue emissions at 453 nm (1D2→3F4). 相似文献
12.
Xi Chen 《Journal of luminescence》2011,131(12):2697-2702
In this work, we report preparation, characterization and luminescent mechanism of a phosphor Sr1.5Ca0.5SiO4:Eu3+,Tb3+,Eu2+ (SCS:ETE) for white-light emitting diode (W-LED)-based near-UV chip. Co-doped rare earth cations Eu3+, Tb3+ and Eu2+ as aggregated luminescent centers within the orthosilicate host in a controlled manner resulted in the white-light phosphors with tunable emission properties. Under the excitation of near-UV light (394 nm), the emission spectra of these phosphors exhibited three emission bands: one broad band in the blue area, a second band with sharp lines peaked in green (about 548 nm) and the third band in the orange-red region (588-720 nm). These bands originated from Eu2+ 5d→4f, Tb3+5D4→7FJ and Eu3+5D0→7FJ transitions, respectively, with comparable intensities, which in return resulted in white light emission. With anincrease of Tb3+ content, both broad Eu2+ emission and sharp Eu3+ emission increase. The former may be understood by the reduction mechanism due to the charge transfer process from Eu3+ to Tb3+, whereas the latter is attributed to the energy transfer process from Eu2+ to Tb3+. Tunable white-light emission resulted from the system of SCS:ETE as a result of the competition between these two processes when the Tb3+ concentration varies. It was found that the nominal composition Sr1.5Ca0.5SiO4:1.0%Eu3+, 0.07%Tb3+ is the optimal composition for single-phased white-light phosphor. The CIE chromaticity calculation demonstrated its potential as white LED-based near-UV chip. 相似文献
13.
B.M. Mothudi O.M. Ntwaeaborwa A. Kumar K. Sohn H.C. Swart 《Physica B: Condensed Matter》2012,407(10):1679-1682
Long persistent SrAl2O4:Eu2+ phosphors co-doped with Dy3+ were prepared by the solid state reaction method. The main diffraction peaks of the monoclinic structure of SrAl2O4 were observed in all the samples. The broad band emission spectra at 497 nm for SrAl2O4:Eu2+, Dy3+ were observed and the emission is attributed to the 4f65d1 to 4f7 transition of Eu2+ ions. The samples annealed at 1100–1200 °C showed similar broad TL glow curves centered at 120 °C. The similar TL glow curves suggest that the traps responsible for them are similar. The long afterglow displayed by the phosphors annealed at different temperatures, may be attributed to the Dy3+ ions acting as the hole trap levels, which play an important role in prolonging the duration of luminescence. 相似文献
14.
In the present paper, KMgSO4Cl:Ce3+, KMgSO4Cl:Ce3+,Dy3+, and KMgSO4Cl:Ce3+,Mn2+, new halosulphate phosphors were synthesized by wet chemical method. X-ray powder diffraction (XRD) and photoluminescence (PL) characterization of phosphors have been reported in this paper. The effects of Dy3+ co-doping on the PL characteristics of KMgSO4Cl:Ce phosphor were studied. Energy transfer from Ce3+→Dy3+and Ce3+→Mn2+ results in increase in PL peak intensity suggesting that Ce3+ plays an important role in PL emission in the present matrix. The PL emission spectra have two peaks (482 and 571 nm) and a single peak (564 nm), which could be attributed to the Ce3+→Dy3+and Ce3+→Mn2+ emissions, respectively. 相似文献
15.
Oxonitridosilicate phosphors with compositions of (Y1−xCex)2Si3O3N4 (x=0−0.2) have been synthesized by solid state reaction method. The structures and photoluminescence properties have been investigated. Ce3+ ions have substituted for Y3+ ions in the lattice. The emission and excitation spectra of these phosphors show the characteristic photoluminescence spectra of Ce3+ ions. Based on the analyses of the diffuse reflection spectra and the PL spectra, a systematic energy diagram of Ce3+ ion in the forbidden band of sample with x=0.02 is given. The best doping Ce content in these phosphors is ∼2 mol%. The quenching temperature is ∼405 K for the 2 mol% Ce content sample. The luminescence decay properties were investigated. The primary studies indicate that these phosphors are potential candidates for application in three-phosphor-converted white LEDs. 相似文献
16.
A series of green phosphors Zn1.92−2xYxLixSiO4:0.08Mn2+ (0≤x≤0.03) were prepared by solid-state synthesis method. Phase and lattice parameters of the synthesized phosphors were characterized by powder X-ray diffractometer (XRD) and the co-doped effects of Y3+/Li+ upon emission intensity and decay time were investigated under 147 nm excitation. The results indicate that the co-doping of Y3+/Li+ has favorable influence on the photoluminescence properties of Zn2SiO4:Mn2+, and the optimal photoluminescence intensity of Zn1.90Y0.01Li0.01SiO4:0.08Mn2+ is 103% of that of commercial phosphor when the doping concentration of Y3+/Li+ is 0.01 mol. Additionally, the decay time of phosphor is much shortened and the decay time of Zn1.90Y0.01Li0.01SiO4:0.08Mn2+ is 3.39 ms, shorter by 1.83 ms than that of commercial product after Y3+/Li+ co-doping. 相似文献
17.
A series of Dy3+-doped calcium magnesium silicate phosphors: CaMgSi2O6:Dy3+, Ca2MgSi2O7:Dy3+, and Ca3MgSi2O8:Dy3+ with white long-lasting afterglow were prepared and investigated. The characteristic intra-configurational 4f emissions of Dy3+ were observed in the emission spectra as well as the afterglow spectra under ultraviolet excitation. The combination of the 480 nm blue emission corresponding to the 4F9/2→6H15/2 transition and the 575 nm yellow emission corresponding to the 4F9/2→6H13/2 transition yielded white-light emission. The white-coloured afterglow emission can last more than 1 h for most of the samples under study. The concentration dependence of the ratio of the yellow emission intensity with blue emission intensity was also examined and found to be varied for the different hosts. The thermoluminescence spectra above room temperature are employed for the discussion of the origin of the traps and the mechanism of the persistent luminescence. 相似文献
18.
A novel green phosphor, Tb3+ doped Bi2ZnB2O7 was synthesized by conventional solid state reaction method. The phase of synthesized materials was determined using the XRD, DTA/TG and FTIR. The photoluminescence characteristics were investigated using spectrofluorometer at room temperature. Bi2ZnB2O7:Tb3+ phosphors excited by 270 nm and 485 nm wavelengths. The emission spectra were composed of three bands, in which the dominated emission of green luminescence Bi2ZnB2O7:Tb3+ attributed to the transition 5D4 → 7F5 is centered at 546 nm. The dependence of the emission intensity on the Tb3+ concentration for the Bi2−xTbxZnB2O7 (0.01 ≤ x ≤ 0.15) was studied and observed that the optimum concentration of Tb3+ in phosphor was 13 mol% for the highest emission intensity at 546 nm. 相似文献
19.
Yue Tian Baojiu Chen Bining Tian Jiashi Sun Xiangping Li Jinsu Zhang Lihong Cheng Haiyang Zhong Hua Zhong Qingyu Meng Ruinian Hua 《Physica B: Condensed Matter》2012,407(13):2556-2559
Micro-sized NaY(MoO4)2:Tb3+ phosphors with dendritic morphology was synthesized by a ionic liquid-assisted hydrothermal process. X-ray diffraction (XRD) indicated that the as-prepared product is pure tetragonal phase of NaY(MoO4)2. Field emission scanning electron microscopy (FE-SEM) images showed that the as-prepared NaY(MoO4)2:Tb3+ phosphors have dendritic morphology. The photoluminescent (PL) spectra displayed that the as-prepared NaY(MoO4)2:Tb3+ phosphors show a stronger green emission with main emission wavelength 545 nm corresponding to the 5D4→7F5 transition of Tb3+ ion, and the optimal Tb3+ doping concentration for obtaining maximum emission intensity was confirmed to be 10 mol%. Based on Van Uitert's and Dexter's models the electric dipole–dipole (D–D) interaction was confirmed to be responsible for the concentration quenching of 5D4 fluorescence of Tb3+ in the NaY(MoO4)2:Tb3+ phosphors. The intrinsic radiative transition lifetime of 5D4 level is found to be 0.703 ms. 相似文献
20.
Non-radiative energy transfers (ET) from Ce3+ to Pr3+ in Y3Al5O12:Ce3+, Pr3+ and from Sm3+ to Eu3+ in CaMoO4:Sm3+, Eu3+ are studied based on photoluminescence spectroscopy and fluorescence decay patterns. The result indicates an electric dipole-dipole interaction that governs ET in the LED phosphors. For Ce3+ concentration of 0.01 in YAG:Ce3+, Pr3+, the rate constant and critical distance are evaluated to be 4.5×10−36 cm6 s−1 and 0.81 nm, respectively. An increase in the red emission line of Pr3+ relative to the yellow emission band of Ce3+, on increasing Ce3+ concentration is observed. This behavior is attributed to the increase of spectral overlap integrals between Ce3+ emission and Pr3+ excitation due to the fact that the yellow band shifts to the red spectral side with increasing Ce3+ concentration. In CaMoO4:Sm3+, Eu3+, Sm3+-Eu3+ transfer occurs from 4G5/2 of Sm3+ to 5D0 of Eu3+. The rate constant of 8.5×10−40 cm6 s−1 and the critical transfer distance of 0.89 nm are evaluated. 相似文献