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1.
The BaGd_(2-2 x)Eu_(2 x)O_4(BG, x = 0.01-0.09) phosphors were successfully synthesized via the sol-gel method,and BaY_(2-2 y)Eu_(2 y)O_4(BY, y = 0.005-0.07) phosphors were included for comparison. The pure phase BG phosphors with the ordered CaFe_2 O_4-type structure are obtained by annealing at 1300℃ for5 h. The phosphors with uniform particle size of 120 nm and good dispersion display typical Eu~(3+)emission with the strongest peak at 613 nm(~5 D_0→~7 F_2 transition of Eu3+) under optimal excitation band at 262 nm(CTB band). The presence of Gd~(3+) excitation bands on the PLE spectra monitoring the Eu3+emission directly proves an evidence of Gd~(3+)-Eu~(3+) energy transfer. Owing to the concentration quenching, the optimum content of Eu3+ addition is 5 at%(x = 0.05), and the quenching mechanism is determined to be the exchange reaction between Eu3+. All the BG samples have similar color coordinates and temperature of(0.64 ± 0.02, 0.36 ± 0.01) and 2000 ± 100 K,respectively. The lifetime value of BaGd_(1.9)Eu_(0.1)O_4 for 613 nm is fitted to be 2.19 ± 0.01 ms, and the Eu~(3+) concentration does not change the lifetime significantly. Owing to the Gd~(3+)-Eu~(3+) energy transfer, the luminescent intensity of the BaGd_(1.9)Eu_(0.1)O_4 phosphor is better than BY system. The BG system served as a new type of phosphor is expected to be widely used in lighting and display areas.  相似文献   

2.
In this work,combustion synthesis was used for the first time to fabricate a phosphor material with red emission for applications in solid-state white-light lamps.We synthesized a material with emission wavelength at λem=617 nm,excited under long UV-blue wavelength based on Eu3+,Tb3+-activated molybdates Li3Ba2(La1-x-yEuxTby)3(MoO4)8 with 0 ≤ x ≤1 and 0 ≤ y ≤ 1.A series of pow...  相似文献   

3.
In this work, the Gd3+/Eu3+ activated Ba3Y4O9 (BYO) phosphors were successfully synthesized via coprecipitation method at 1400 °C. The precursor composition, crystal structure stability, microscopic morphology, photoluminescence (PL)/photoluminescence excitation (PLE) spectra and fluorescence attenuation analysis of the phosphors are discussed in detail. The chemical composition of the precursor was determined by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry (TG) analysis; According to field emission-scanning electron microscopy (FE-SEM) analysis, it is found that the particle size of phosphor is uniform and the agglomeration is few. According to PL/PLE spectra analysis, Ba3Y3.28Eu0.6Gd0.12O9 phosphors has the strongest excitation band at 260 nm and the strongest emission band at 614 nm, and the fluorescence intensity of Ba3Y3.28Eu0.6Gd0.12O9 is higher than that of Ba3Y3.4Eu0.6O9. The quenching concentration of Eu3+ in Ba3Y3.88–4xEu4xGd0.12O9 phosphors is x = 0.15 and the mechanism of quenching concentration of Eu3+ is electric dipole-quadrupole type interactions. The lifetime value of Ba3Y3.88–4xEu4xGd0.12O9 (x = 0.15) phosphors is 0.686 ms and decreases with the increase of Eu3+ content. In addition, the CIE chromaticity diagram of Ba3Y3.28Eu0.6Gd0.12O9 phosphors is (0.66, 0.34). Finally, the lamp beads assembled with Ba3Y3.28Eu0.6Gd0.12O9 phosphors have an ideal luminous effect. Therefore, the Ba3Y3.88–4xEu4xGd0.12O9 phosphors designed in this work may hopefully meet the requirements of various lighting and optical display applications.  相似文献   

4.
A series of Gd5Si2BO13:Eu3+ and non-rare earth Bi3+ ions doped Gd5Si2BO13:Eu3+ phosphors was successfully synthesized via high-temperature solid-state method,and the as-obtained phosphors were studied on their phase structures,luminescence characteristics,thermal stability and luminescence lifetime.Transient fluorescence spectroscopy data show that the addition of Bi3+ can obviously enha...  相似文献   

5.
A series of red-emitting phosphors of CaBi2Ta2O9:Pr3+ and CaBi2Ta2O9:Eu3+ were synthesized by the solid-state reaction method. The crystal structure and photoluminescence properties were investigated by X-ray diffraction (XRD) and photoluminescence spectra. The emission spectra showed that the red emission peaks were located at 622 nm for Pr3+ and 615 nm for Eu3+, respectively. The optimal doping concentrations for Ca1?xBi2Ta2O9:xPr3+ and Ca1?yBi2Ta2O9:yEu3+ were x=0.02 and y=0.15, respectively. The effect of fluxes (H3BO3, NH4F, CaCl2 and CaF2) and charge compensations (Li2CO3, Na2CO3 and K2CO3) on luminescent properties were investigated in detail. It was found that the relative emission intensity of Ca0.98Bi2Ta2O9:0.02Pr3+ with 10 mol.% H3BO3 flux was about 2.9 times higher than that of the sample without flux. The relative emission intensity of Ca0.7Bi2Ta2O9:0.15Eu3+, 0.15K+ was about the 2.1 times higher than that of Ca0.85Bi2Ta2O9:0.15Eu3+.  相似文献   

6.
In this paper, we report synthesis of pure SrMoO4, Sm3+ (1 at%–5 at%) doped SrMoO4 and Bi3+ (1 at%–3 at%) co-doped in 4 at% Sm3+ doped SrMoO4 (SrMoO4:4Sm3+) phosphors by solution combustion method. The X-ray diffraction (XRD) analysis reveals the tetragonal phase of all samples, also Bi3+ co-doping supports crystallite size growth and reduces lattice strain. Absorption analysis of Sm3+ doped SrMoO4 ascertains a decrease in band gap and Bi3+ co-doping confirms the emergence of an absorbance peak at around 308 nm attributed to Bi3+ energy levels. Photoluminescence (PL) analysis ascertains an increase in emission peaks for Sm3+ doped SrMoO4 up to 4% concentration, which are attributed to an electron transition from 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, and 11/2) energy levels of Sm3+ ions. We have explained the effects of Bi3+ co-doping on the luminescence of Sm3+ doped SrMoO4. The reduced microstrain and increased crystallinity of the phosphors as a result of Bi3+ co-doping and their correlation with the luminescence of Sm3+ ions are discussed.  相似文献   

7.
A series of new double perovskite La2–xEuxCaSnO6 (0 ≤ x ≤ 0.8) red phosphors were synthesized by traditional solid-state reaction. The phase, microstructure, photoluminescence (PL) properties, quantum efficiency, and thermal stability of the phosphors were investigated. La2CaSnO6 matrix has a monoclinic double perovskite structure with space group P21/n. Under near-ultraviolet (UV) light at 395 nm, La2–xEuxCaSnO6 phosphors exhibit the most typical red emission peak at 614 nm, which corresponds to 5D07F2 electric dipole transition of Eu3+. The optimum Eu3+ doping content is attained at x = 0.5, and the La1.5Eu0.5CaSnO6 phosphor shows a moderate quantum efficiency (32.3%) and high color purity (92.2%). Besides, the temperature-dependent spectrum of the phosphor was studied. The emission intensity of Eu3+ at 423 K decreases to 70.94% of the initial intensity at 303 K, and the activation energy ΔE is estimated to be 0.232 eV, suggesting that the phosphors possess good thermal stability. The fabricated w-LED based on the phosphors has higher Ra (89), lower CCT (4539K), and better chromaticity coordinates (0.371, 0.428). These results prove that the Eu3+-doped La2CaSnO6 red phosphor has great potential applications in w-LEDs.  相似文献   

8.
Green emitting Eu2+-doped (Ba3_xSrx)Si6012N2 solid solutions were synthesized through solid state reaction at 1350 ℃ for 10 h under a N2/H2 atmosphere. The XRD patterns revealed that the solid solution series of (Ba3 x-ySrx)Si6Ol2N2:yEu2+ with x value ranging from 0-0.6 were established. An efficient and intense tunable green light was observed by varying the cation Sr/Ba ratio. The emission spectra exhibited an entire shift towards long wavelength with increasing ofx value, which was caused by large crystal field splitting and Stokes shift. The x value dependence of emission intensity was discovered and explained by the enhanced probability of electron from excited 4f state to 5d ground state via nonradioactive transition. Highly thermal stability and feasible color coordinates were verified. White LEDs with excellent photochromic properties were fabricated by packing GaN based blue chips and (Ba Sr)3Si6012N2:Eu2+ phosphors. All results indicated that the (Ba3_xSrx)SirO12N2:Eu2+ phosphors were confirmed to be a promising candidate for pc-white LEDs in solid state lighting.  相似文献   

9.
In order to effectively improve the afterglow properties of CaAl_2 O_4:Eu~(2+),Nd~(3+) phosphors,a series of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)(x=0,0.012,0.024,0.036,0.048,0.060 mol) phosphors were prepared by a high-temperature solid-phase approach.Crystalline composition and microstructure were characterized by XRD,TEM,HRTEM,and XPS,luminescence properties were systematically analyzed by fluorescence spectra,afterglow decay curves and TL glow curve.Results show that all of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)phosphors belong to monoclinic CaAl_2 O_4,without other cystalline phase.The blue emission at 442 nm is observed,which is assigned to the 4 f~65 d→4 f~7 transition of Eu~(2+) ions.Doping with appropriate amount of Gd~(3+) ions(x=0.036 mol) significantly improves the afterglow properties of phosphors,but the excessive doping of Gd~(3+) induces the fluorescent quenching.The doping of moderate Gd3+changes the traps states,the trap depth varies from 0.598 to 0.644 eV and the trap concentration is also greatly improved,thus significantly improving afterglow performance.  相似文献   

10.
This work presents the synthesis of Y2O3:Eu3+,xCa2+ (x = 0 mol%, 1 mol%, 3 mol%, 5 mol%, 7 mol%, 9 mol%, 11 mol%) nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic, display, and lighting applications. The X-ray diffraction (XRD) patterns of the proposed nanophosphor reveal its structural properties and crystalline nature. The transmission electron microscope (TEM) results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca2+. Fourier transform infrared spectroscopy (FTIR) and Raman vibrations also confirm the presence of Y–O vibration and subsequently explain the crystalline nature, structural properties, and purity of the samples. All the synthesized nanophosphors samples emit intense red emission at 613 nm (5D07F2) under excitation with 235, 394 and 466 nm wavelengths of Eu3+ ions. The photoluminescence (PL) emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength, respectively. The emission intensity of Y2O3:Eu3+,xCa2+ (5 mol%) is increased 8-fold as compared to Eu:Y2O3. Doping with Ca2+ ions enhances the emission intensity of Eu:Y2O3 nanophosphors due to an increase in energy transfer in Ca2+→Eu3+ through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix. It is also observed that the optical band gap and the lifetime of the 5D0 level of Eu3+ ions in Y2O3:Eu3+,xCa2+ nanophosphor sample gets changed with a doping concentration of Ca2+ ions. Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%, respectively. CIE, CCT, and color purity values (>98%) show an improved red-emitting nanophosphor in the warm region of light, which makes this material superior with a specific potential application for UV-based white LEDs with security ink, display devices, and various other optoelectronics devices.  相似文献   

11.
The Bi3+ doped molybdate-based red-emitting phosphors, LiEu1-xBix(MoO4)2, were successfully synthesized with a sol-gel method. The prepared LiEu1-xBix(MoO4)2 phosphors exhibited pure and intense red emission at 613 nm under the excitation of near-UV 394 nm. It was discussed in detail that the influence of the synthesis conditions such as the doping concentration of Bi3+, the dose of citric acid, pH of the precursor solution and the sintering temperature on the emission intensity of the phosphors. According to the results, the optimal condition was obtained: the doping concentration of Bi3+ was 15 mol.%, molar ratio of citric acid to metal ions was 1.5:1, pH of the precursor solution was 1.0 and the sintering temperature was 800 ?C. The X-ray diffraction (XRD) patterns of the LiEu0.85Bi0.15(MoO4)2 phosphor prepared under the optimal condition indicated that the phosphor was single phase with tetragonal scheelite structure. The Commission Internationale de l’E-clairage (CIE) chromaticity coordinates of LiEu0.85Bi0.15(MoO4)2 were (x=0.655, y=0.345), which were closer to the national television stan-dard committee (NTSC) standard values (x=0.670, y=0.330) than that of a commercial red phosphor of Y2O2S:Eu3+(x=0.630, y=0.350). This LiEu0.85Bi0.15(MoO4)2 red phosphor is a promising candidate for the fabrication of white light-emitting diode (W-LED) with near-UV chips.  相似文献   

12.
Eu2+,Dy3+ and Zr4+ ions co-doped strontium aluminate(i.e.,SrAl2O4:Eu2+,Dy3+,Zr4+)/molybdate(i.e.,Ho2MoO6 or Nd2MoO6) with photo-/mechano-luminescence and allochroic effect as multi-optical functional hybrid pigments were prepared via solid state reactions and subsequent mixing.The phosphor and hybrid pigments were characterized by X-ray diffraction,scanning electron...  相似文献   

13.
The luminescent properties of Sr2.97MgSi2O8:Eu2+0.01 phosphors were investigated with different Ln3+0.02(Ln3+:Dy3+,Er3+,Ho3+) co-dopants. The co-dopants had no influence on both the structure of the lattice and the position of the emission peak. However, the afterglow properties of samples were enhanced with different co-dopants. The afterglow duration of the Dy3+ co-doped sample was longer than that of the others. Furthermore, the co-doping samples had stronger thermoluminescence (TL) intensity and therefore longer afterglow duration. At last, the self-reduction of Eu3+→Eu2+ was observed in an silicate compound of Sr3-xMgSi2O8:xEu phosphor in air condition. This is the first time to show a blue long afterglow phosphor synthesized avoiding reducing atmosphere.  相似文献   

14.
In this work,calcium niobium gallium garnet(Ca3 Nb1.6875Ga3.1875O12-CNGG) ceramic samples singledoped with Tb3+ and co-doped with Tb3+ and Yb3+ ions were sintered by the solid-state reaction method.The structural characterization of the samples was carried out by X-ray diffraction measurements.The optimal concentration of Tb3+ ions corresponding to the maximum luminescence in the green spectral range in CNGG:...  相似文献   

15.
A series of Tb~(3+) and Eu~(3+) co-doped NaY(WO_4)_2 phosphors were synthesized by hydrothermal reactions.The crystal structure,morphology,upconversion luminescent properties,the energy transfer from Tb~(3+) to Eu~(3+)ions and the ~5 D_4→ ~7 F_5 transition of the Tb~(3+) ion in NaY(WO_4)_2:Tb~(3+),Eu~(3+) phosphors were investigated in details.The results indicate that all the synthesized samples are of pure tetragonal phase NaY(WO_4)2.Furthermore,the micrometer-sized needle spheres and excellent dispersion of the particles are obtained by adding polyethylene glycol(PEG-2000) as the surfactant.Phosphors of NaY(WO_4)_2:Tb~(3+),Eu~(3+) exhibit the492 nm blue emission peak,546 nm green emission peak,595 nm orange emission peak and 616 nm red emission peak under 790 nm excitation.The energy transfer from Tb~(3+) to Eu~(3+) is a resonant transfer,in which electric dipole-dipole interaction plays a leading role.By adjusting the doping concentration of Eu~(3+) in NaY(WO_4)_2: 1.0 mol%Tb~(3+),xmol%Eu~(3+) phosphors,the emitting color of UC phosphors can be tuned from green to red.  相似文献   

16.
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-→Eu3+. 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-→Gd3+. 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 Eu3+. When excited with 254 nm, the integral emission intensity of Eu3+ increased after Al3+ or Sc3+ substituting Gd3+ partly in BaGd0.9Eu0.1B9O16. Under 147 nm excitation, the integral emission intensity of Eu3+ decreased after some Gd3+ was replaced by Sc3+, but increased after adding appropriate Al3+ into BaGd0.9Eu0.1B9O16.  相似文献   

17.
A broadband blue-emitting Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro perties,external quantum efficiency,the rmal stability and application perfo rmance of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+),by partially substituting Sr~(2+) with Ca~(2+)(x=0-0.2),were studied by various analytical techniques.When the Ca/Sr ratio of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) gradually increases,the emission peak of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) red-shiftes from 459 to 465 nm,corrected external quantum efficiency increases from 31.8% to 42.9%,and the thermal stability is also improved.The mechanism of the changes of the photoluminescence emission and excitation spectra,external quantum efficiency and thermal stability properties was also investigated in detail.In addition,a w-LED was fabricated by using SrLu_2 O_4:Ce~(3+)(blue),β-sialon:Eu~(2+)(green) and(Sr,Ca)AlSiN_3:Eu~(2+)(red) phosphors combined with a 405 nm near-UV LED chip,and its color rendering index(CRI) reaches 96.0.When Sr_(0.8)Ca_(0.2)Lu_2 O_4:Ce~(3+)is applied as blue phosphor to substitute SrLu_2 O_4:Ce~(3+),the obtained w-LED devices have high luminous efficiency,and CRI greater than 95.0.These re sults show that the Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.  相似文献   

18.
Gd2InSbO7:Eu3+ red phosphors were successfully synthesized via high-temperature solid–state reaction. The phase purity, particle size, and luminescence properties of obtained phosphors were measured and analyzed in detail. The Gd2InSbO7 lattice possesses cubic structure with Fd-3m (227) space group. The phosphors emit bright red emission at 628 nm under 393 nm excitation, and this phenomenon is attributed to the 5D07F2 transition. The Judd–Ofelt parameters (Ω2, Ω4), transition ratio, and branching ratios (β) of Eu3+-doped Gd2InSbO7 phosphor were calculated on the basis of the emission spectra and decay lifetimes. The optimal content in Gd2InSbO7:xEu3+ is identified to be 15 mol%. The thermal quenching of Gd2InSbO7:Eu3+ is found to be over 500 K, and its activation energy is 0.26 eV. The Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of Gd2InSbO7:15%Eu3+ are (0.629, 0.371), which are close to ideal red chromaticity coordinates (0.670, 0.330). The fabricated w-LED exhibits good color rendering index (Ra) (86), correlated color temperature (CCT) (6997 K), and CIE chromaticity coordinates (0.302, 0.330). The obtained results demonstrate that Gd2InSbO7:Eu3+ phosphors have potential applications in white LEDs.  相似文献   

19.
The hardystonite phosphors of Eu2+ activated M2ZnSi2O7 (M=Sr, Ba) were synthesized by combustion-assisted method. They were systematically characterized by photoluminescence excitation and emission spectra. The emission spectra of these two phosphors showed that the main emission peaks are at 475 and 503 nm due to 4f65d1→4f7 transition of Eu2+. Both phosphors could be efficiently excited in the wavelength range of 250-425 nm where the near ultraviolet light-emitting diode was well matched. The (x, y) color coordinates were determined with the emission values (x, y)=(0.41, 0.21) and (0.16, 0.45) for the M2ZnSi2O7: Eu2+ (M=Sr, Ba) phosphors.  相似文献   

20.
Rare earth (RE) pentaborates, both α- and β-polymorphs, are good candidates for photoluminescent hosts suitable for various RE activators. Ce3+ acts not only as an activator itself, but also as a sensitizer to other rare earth activators, like in the case of commercial green phosphor CeMgAl11O19:Tb3+. In this work, two solid solutions of β-La0.9–xCe0.1TbxB5O9 (0 ≤ x ≤ 0.15) and β-La0.9–yCe0.1DyyB5O9 (0 ≤ y ≤ 0.07) were prepared by sol–gel method with high crystallinity, and the phase purity was confirmed with careful analyses on powder X-ray diffraction patterns. Energy transfers are expected due to the overlapping of Ce3+ emission with the Tb3+/Dy3+ excitation. Indeed, the steady photoluminescence spectra indicate the decrease of the Ce3+ emission and the increase of the Tb3+/Dy3+ emission, and the fluorescence decay curves exhibit the decrease of the average lifetime of Ce3+. The energy transfer efficiency is estimated to be 60% at x = 0.15 and 55% at y = 0.07, respectively. The mechanism is likely through the dipole–dipole electric interactions for both cases. With this rationale, the Tb3+ and Dy3+ emissions are greatly enhanced, in particular, the white emission of Dy3+ in β-La0.85Ce0.1Dy0.05B5O9 is enhanced by 20 times.  相似文献   

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