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1.
Intense red-emitting phosphors for LED solid-state lighting 总被引:1,自引:0,他引:1
Xiao-xiao Wang 《Materials Research Bulletin》2007,42(9):1669-1673
The phosphors Gd2−xEux(MoO4)3 (x = 0.20, 0.40, 0.60, 0.80, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0), Gd0.8−xYxEu1.2(MoO4)3 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8) and Gd0.2Y0.6−xEu1.2Smx(MoO4)3 (x = 0.02, 0.024, 0.028, 0.032, 0.036, 0.04) were prepared by solid-state reaction technique at 950 °C. The presence of the Y3+ and Sm3+ ions strengthen and broaden the absorption of the phosphors at ∼400 nm. The intense red-emitting phosphor Gd0.2Y0.572Eu1.2Sm0.028(MoO4)3 with orthorhombic structure was obtained. Both Eu3+ and Sm3+ f-f transition absorptions are observed in the excitation spectra, the main emission line is at 616 nm (5D0 → 7F2 transition of Eu3+) and the chromaticity coordinates (x = 0.66, y = 0.33) is very close to the NTSC standard values (x = 0.67, y = 0.33). It is considered to be an efficient red-emitting phosphor for GaN-based light emitting diode (LED). 相似文献
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3.
《Materials Research Bulletin》2013,48(11):4476-4480
CeO2 microspheres, with an average diameter of 1 μm, have been successfully prepared through a facile 1,4-dioxane-assisted solvothermal synthesis, where 1,4-dioxane is acted as a capping agent for the first time. By varying the solvent ratio, the formation mechanism for the CeO2 microspheres has been proposed on an isotropic growth through the capping function of 1,4-dioxane. The strong UV–vis spectra result indicates that the CeO2 microspheres are suitable as an UV blocking and shielding material. The cyclic voltammetric measurements of hemoglobin immobilized on CeO2-Nafion modified glassy carbon electrode reveal a typical characteristic of surface-controlled thin-layer electrochemical behavior of the CeO2 microspheres. 相似文献
4.
New red phosphors, Na5Eu(MoO4)4 doped with boron oxide were prepared by the solid-state reaction. Their structure and photo-luminescent properties were investigated. With the introduction of boron oxide, the red emission intensity of the phosphors under 395 nm excitation is strengthened, with high color-purity (x = 0.673, y = 0.327). The single red light-emitting diode was obtained by combining InGaN chip with the red phosphor, bright red light can be observed by naked eyes from the red light-emitting diodes under a forward bias of 20 mA. 相似文献
5.
The present investigation aims at the luminescence properties of Ca9Y(VO4)7:Eu3+, Bi3+ red phosphor materials. The red emission at 613 nm originating from 5D0–7F2 transition of Eu3+ in Ca9Y(VO4)7 is enhanced strongly with Bi3+–V5+ couple as the sensitizer, under excitation either into the 5L6 state or the 5D2 state. The energy transfer from Bi3+–V5+ to Eu3+ is discussed. For a fixed Eu3+ concentration, there is an optimal Bi3+ concentration with 15 mol%, at which the maximum luminescence intensity of Eu3+ is achieved. The red emission of Ca9Y(VO4)7:0.8Eu3+, 0.15Bi3+ (under 395 nm and 465 nm excitations) is stronger than that of commercial Y2O3:Eu3+ phosphor (under 395 nm and 467 nm excitations). Based on the ratios of the red emission at 613 nm to orange one at 592 nm, it is considered that the symmetry of Eu3+ site decreases with doping of Bi3+, leading to more opposite parity components. Lifetime and diffuse reflection spectra measurements indicate that the red emission enhancement is due to the enhanced transition probabilities from the ground state to 5L6 and 5D2 states of Eu3+ in the distorted crystal field. Therefore the present material is a promising red-emitting phosphor for white-light diodes with near-ultraviolet/blue GaN-based chips. 相似文献
6.
Phosphors of La2TeO6 doped with Eu3+ ions have been synthesized by the oxidation of the corresponding rare-earths oxytellurides of formula La2−xEuxO2Te (x = 0.02, 0.06, and 0.1) at 1050 K. Powder X-ray diffraction confirms that the as prepared materials consist of the orthorhombic La2TeO6 as main phase. The photoluminescence (PL) of red-emitting La2−xEuxTeO6 powder phosphors is reported. The emission spectrum, exhibits an intense emission peak due to 5D0 → 7F2 transition at 616 nm, which indicates that the Eu3+ ion occupies a non-centrosymmetric site in the host lattice. These materials could find application for use as lamp phosphors in the red region. 相似文献
7.
Yurong Shi 《Materials Research Bulletin》2011,46(7):1148-1150
Novel red phosphors Na2CaSiO4:xEu3+ were synthesized using high temperature solid-state reaction and their luminescence characteristics were investigated for the first time. The excitation spectra indicate that the Na2CaSiO4:xEu3+ phosphors can be effectively excited by ultraviolet (393 nm) light. The emission spectra of Na2CaSiO4:xEu3+ phosphors invariably exhibit four peaks assigned to the 5D0-7FJ (J = 1, 2, 3 and 4) transitions of Eu3+ under 393 nm excitation. The Commission Internationale de l’Eclairage (CIE) chromaticity coordinates and quantum efficiency (QE) are (0.66, 0.34) and 58.9%, respectively. The good color saturation and high quantum efficiency indicate that Na2CaSiO4:Eu3+ phosphors are potential candidate for light-emitting diodes. 相似文献
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ZnS:Cu,Cl phosphors were prepared by conventional solid state reaction with the aid of NaCl-MgCl2 flux. The copper activator was introduced into the phosphor precursors by three different methods: co-precipitated with ZnS (CP), wet-coated onto ZnS powders (WC), and simply mixed with ZnS in a mortar (SM). The samples were characterized by X-ray powder diffraction, photoluminescence spectra and X-ray excited luminescence spectra. The results show that both photo- and X-ray excited luminescence intensities of the as-prepared ZnS:Cu,Cl phosphors are in the decreasing order of CP > WC > SM. The different copper activator distribution in the phosphors resulting from the different methods was the main reason responsible for the different luminescence intensity, and uniform distribution is beneficial to the luminescence of the phosphors. 相似文献
9.
Eu2+-doped borate fluoride BaAlBO3F2 was synthesized by the conventional high temperature solid state reaction. The crystal phase formations were confirmed by X-ray powder diffraction (XRD) measurements and the structure refinement. The photoluminescence (PL) excitation and emission spectra, and the decay curves were investigated. Eu2+-doped BaAlBO3F2 phosphor can be efficiently excited by near-UV light and presents narrow blue luminescence band centered at 450 nm. The maximum absolute quantum efficiency (QE) of BaAlBO3F2:0.05Eu2+ phosphor was measured to be 76% excited at 398 nm light at 300 K. The thermal stability of the blue luminescence was evaluated by the luminescence decays as a function of temperature. The phosphor shows an excellent thermal stability with high thermal activation-energy on temperature quenching effects because of the rigid crystal lattices. 相似文献
10.
A novel phosphor K2Gd(WO4)(PO4):Tb was prepared via a solid-state reaction. The crystal structure of K2Gd(WO4)(PO4) as a new host matrix for luminescence was defined to be the orthorhombic system with space group Ibca (73). Visible quantum cutting under Tb3+ 4f8–4f75d1 excitation and host excitation in K2Gd(WO4)(PO4):Tb3+ via a downconversion was identified. In order to rationalize the quantum cutting effect, the proper mechanism was proposed. According to calculations, the quantum efficiency was up to 183.2% and 176.4% under excitation at 235 nm and 150 nm, respectively. When compared with Zn2SiO4:Mn2+ (P1-G1S), KGWP:0.5Tb3+ is slightly less bright over 450–650 nm but has a shorter decay time. 相似文献
11.
The photoluminescent properties of a series of Tb3+-doped Na3GdP2O8 phosphors excitable by vacuum ultraviolet and ultraviolet light are reported. The host related absorption, f-f and f-d transitions of Gd3+ and Tb3+, and charge transfer of O2− → Gd3+ and O2− → Tb3+ are assigned. Under 147 nm light excitation, Na3GdP2O8:Tb3+ phosphors show efficient green emissions with a dominant peak at 545 nm. The optimal sample Na3Gd0.4Tb0.6P2O8 shows a shorter decay time and a comparable brightness when compared with the commercial Zn2SiO4:Mn2+ green phosphor. These results demonstrate that it is a potential candidate for plasma display panels application. 相似文献
12.
New red Ca10K(PO4)7:Eu3+, K+ phosphors were synthesized by solid state reaction and their photoluminescence properties as well as those by co-doping Mo6+ under near ultraviolet excitation were investigated. From the excitation spectra monitored at 611 nm, it can be seen that the strongest excitation peak is situated at 393 nm, well matching with the emission wavelength of near-ultraviolet chips for white LEDs. Upon 393 nm excitation, the brightness of Ca9K(PO4)7:0.5Eu3+, 0.5 K+ with the optimal Eu3+-doping concentration is about 2.3 times stronger than that of the commercial red Y2O3:Eu3+ phosphor. The introducing of Mo6+, which results in a possible variety for the excited energy level of the host, can enhance the brightness of Eu3+ to be maximized by about 15%. The CIE chromaticity coordinates of Ca9K(PO4)7:0.5Eu3+, 0.5 K+ are calculated to (0.654, 0.345), which are close to the (0.67, 0.33) standard of the National Television System Committee. All the above results indicate Eu3+-activated Ca10K(PO4)7 is a potential candidate for white LEDs. 相似文献
13.
Novel Eu2+-doped bromosilicate phosphors, (CaO-CaBr2-SiO2):0.03Eu2+, were prepared by the traditional solid-state method under a different calcination temperature. The as-prepared (CaO-CaBr2-SiO2):0.03Eu2+ phosphors obtained under various reaction temperatures all indicated a broad excitation in the near ultraviolet region (350-450 nm). The phosphor system exhibits bluish-green light with a peak wavelength at 498 nm when the calcination temperature is below 800 °C, while it shows a strong blue emission light with a peak wavelength at 474 nm as the calcination temperature is above 800 °C, and it also gives an interesting greenish-yellow long-lasting phosphorescence with a peak wavelength at 540 nm in the dark. 相似文献
14.
《Materials Research Bulletin》2013,48(11):4749-4753
A series of single-phased emission tunable NaBa4(BO3)3:Ce3+, Tb3+ phosphors were synthesized by solid-state reaction. The crystal structure, photoluminescence properties, concentration quenching and energy transfer of NaBa4(BO3)3:Ce3+, Tb3+ were systematically investigated. The wavelength-tunable bluish-green light can be realized by coupling the emission bands centered at 425 and 543 nm ascribed to the contribution from Ce3+ and Tb3+, respectively. The energy transfer from Ce3+ to Tb3+ in NaBa4(BO3)3 host was studied and demonstrated to be a resonant type via a dipole–dipole interaction mechanism. The energy transfer efficiency (Ce3+ → Tb3+) obtained by decay curves was consistent with the result calculated by the emission intensity, which gradually increased from 0% to 84.5% by increasing the Tb3+ doping content from 0 to 0.45. The results indicate that the NaBa4(BO3)3:Ce3+, Tb3+ phosphors have potential applications as an ultraviolet-convertible phosphor due to its effective excitation in the ultraviolet rang. 相似文献
15.
The effect of hydrostatic pressure (varying up to 91 kbar) at room temperature emission spectra and fluorescence lifetime of the Cr3+ R1 line (2E → 4A2 transition) in tiospinel ZnAl2S4 was studied for the first time. The studies performed reveal the shift of the R1 line with increasing pressure. Such a red shift was accompanied by a significant change of the fluorescence lifetime. Both trends were successfully explained by a simple model, which resulted in adequate agreement between the calculated and the observed. 相似文献
16.
Porous TiO2-based nanofiber was fabricated via a combined electrospinning and alkali-dissolution method. TiO2/SiO2 composite nanofiber was firstly prepared by electrospinning and sintering, and then silica was leached out with alkaline solution from the bulk of TiO2/SiO2 composite nanofiber to produce porous microstructure. The thermal decomposition and phase structure of the composite nanofiber precursor was investigated with TG/DSC and XRD, and optimal sintering temperature was obtained. SEM-EDX and FT-IR characterization show that most silica can be dissolved out from the composite nanofiber and thus porous nanofiber with excellent microstructure can be spontaneously formed. The effect of composite nanofiber composition on porous microstructure was studied, and it is found that the composite nanofiber with 20wt% silica can produce better porous microstructure compared to those with 10wt% and 30wt% silica. Meanwhile, porous TiO2 nanofiber with 20wt% silica shows higher degradation efficiency to Congo Red. 相似文献
17.
Yongjun He 《Materials Research Bulletin》2005,40(4):629-634
ZnS hollow microspheres were prepared via a novel emulsifier-free emulsion route for the first time. The aqueous solution of zinc nitrate and the toluene solution of thioacetamide were emulsified under sonication to form water in toluene emulsion, and then the emulsion was processed at elevated temperature under sonication for 45 min, by which ZnS nanoparticles were generated and assembled spontaneously at the surface of water droplets; after the subsequent separation, wash and desiccation process, ZnS hollow microspheres were obtained. ZnS hollow microspheres were characterized by TEM, XRD, UV-vis and particle size analyzer; the effect of the reaction temperature on the products was investigated. The results showed that ZnS hollow microspheres were made up of ZnS nanoparticles and had cubic structures (β-ZnS); with the rise of reaction temperature, the ZnS hollow microspheres became smaller and more compact. This study provided a promising route for the preparation of a variety of hollow microspheres. 相似文献
18.
The degradation behavior of ZnS:Ag, Cl as a phosphor for CL by EB irradiation at 7 kV was examined by TL measurement. After EB irradiation, TL intensity decreased and the TL peak shifted to the lower temperature side. By comparing TL thermograms of mechanically damaged ZnS:Ag, Cl, ZnS:Cl with varying Cl concentration as well as ZnS:Ag, Al after EB irradiation, we conclude that the decrease in the effective concentration of Cl−, serving as active luminescence center, is responsible for the CL degradation of ZnS:Ag, Cl by EB irradiation. 相似文献
19.
Y2O2S co-doped with Bi3+,Eu3+ phosphors were prepared and their luminescence properties under vacuum ultraviolet (VUV) excitation were investigated. Much stronger red emission for Y2O2S:Eu3+,Bi3+ were observed under 147 nm excitation than that for Y2O2S:Eu3+. Investigation on photoluminescence and calculation of electronic structure of Y2O2S:Eu3+,Bi3+ revealed that the Bi3+ acts as a medium in energy transfer process and the great VUV luminescence enhancement of Y2O2S:Eu3+ by doping Bi3+ is due to effective energy transfer process: charge transfer (CT) transition of Y3+-O2− → Bi3+ → Eu3+. The Y2O2S:Eu3+,Bi3+ showed excellent optical properties when compared with the commercial (Y,Gd)BO3:Eu3+. Thus, the Y2O2S:Eu3+,Bi3+ would be a promising VUV-excited red phosphor. 相似文献
20.
Bi2YVO8 was prepared by solid-state reaction for the first time. The structural and photocatalytic properties of Bi2YVO8 were studied. The results showed that this compound has the tetragonal crystal system with space group I4/mmm. The band gap of Bi2YVO8 was estimated to be about 2.09 eV by plotting (αhν)2 versus hν and obtaining the hν axis intercept value according to Tauc's equation. For the photocatalytic water splitting reaction, H2 or O2 evolution was observed from pure water with Bi2YVO8 as the photocatalyst under ultraviolet light irradiation (wavelength = 390 nm). Degradation of aqueous methylene blue photocatalyzed by this compound was investigated under visible light irradiation. Bi2YVO8 showed higher photocatalytic activity compared to Bi2YTaO7, Bi2InTaO7 or TiO2 (P-25). Complete removal of aqueous methylene blue was achieved after visible light irradiation for 170 min. The decrease of the total organic carbon and the formation of inorganic products such as SO42− and NO3− revealed the continuous mineralization of aqueous methylene blue during photocatalytic reaction. 相似文献