首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The luminescent properties of alkaline earth orthosilicates M2SiO4 (M=Ba, Sr, Ca) doped with Eu2+ ions are investigated. Two emission bands are assigned to the f-d transitions of Eu2+ ions doped into two different cation sites in host lattices confirmed by electron paramagnetic resonance signal. Two emission bands show the different emission color variation with substituting M2+ cations with smaller cations. This behavior is discussed in terms of two competing factors of the crystal field strength and covalence. Also the decay times are in order of 600-1000 ns. These phosphors with maximum excitation of around 370 nm can be applied as a color-tunable phosphor for light-emitting diode based on ultraviolet chip/phosphor technology.  相似文献   

2.
Divalent europium-activated strontium orthosilicate Sr2SiO4:Eu2+ and Mg0.1Sr1.9SiO4:Eu2+ phosphors were synthesized through the solid-state reaction technique. Their luminescent properties under ultraviolet excitation were investigated. The X-ray diffraction (XRD) results show that these phosphors are of α′-Sr2SiO4 phase with a trace of β-Sr2SiO4. Doping of Eu2+ ion into the crystal lattice results in the lattice constant being expended, while Mg2+ makes the lattice constant shrinking. A solid solution with the same crystal structure is formed when Eu2+ or Mg2+ substitutes part of Sr2+ ions and occupies the same lattice sites. The Sr2SiO4:Eu2+ phosphors show two emission spectra peaked at 535 and 473 nm originated from the 5d-4f transition of Eu2+ ion doped in two different Sr2+ sites in the host lattice. By substitution of 0.1 mol of Sr2+ with Mg2+, these two emission bands are tuned to be in the blue and yellow region (459 and 564 nm for Mg0.1Sr1.88SiO4:Eu0.02), respectively. The tuning effect is discussed. With a combination of the blue and yellow emission bands the phosphors show white color, indicating that these phosphors may become promising phosphor candidates for white light-emitting diodes (LEDs).  相似文献   

3.
Spherical SiO2 particles have been coated with Zn2SiO4:Eu3+ phosphor layers by a Pechini sol-gel process. The microstructure and luminescent properties of the obtained Zn2SiO4:Eu3+@SiO2 particles were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and lifetime. The results demonstrate that the Zn2SiO4:Eu3+@SiO2 particles, which have regular and uniform spherical morphology, emitted an intensive red light emission at 613 nm under excitation at 395 nm. Besides, the effects of the Eu3+ concentration, annealing temperature and charge compensators of Li+ ions on the PL emission intensities were investigated in detail.  相似文献   

4.
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+5D47FJ and Eu3+5D07FJ 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   

5.
Green-emitting phosphors Ca3SiO4Cl2:Eu2+ were prepared by the high temperature solid-state method. Sol-gel process was adopted to encapsulate the as-prepared phosphors with tetraethylorthosilicate (TEOS) as silicon coating reagent. Fluorescence spectrometer, scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) patterns were employed to characterize the emission spectra, the surface morphologies and the phase structures, respectively. The chemical stability testing was operated by the method of soaking the phosphors in deionized water and roasting them at different temperatures. The results indicated that the surfaces of the green phosphors were evenly coated by SiO2 and the phase structure of the coated phosphors remained the same as the uncoated samples. The luminance centre of Eu2+ did not shift after surface treatment and the luminance intensity of coated phosphors was lower than that of the uncoated samples. The results demonstrated that the water-resistance stability of the coated phosphor was improved to some degree because the pH value and the luminance intensity variation were both smaller than the uncoated phosphor after steeping within the same time. Moreover, the thermal stability of coated phosphors was enhanced obviously compared to the original samples based on the temperature dependent emission spectra measurement.  相似文献   

6.
Zinc silicate phosphors co-doped with Eu3+ ions and also with both Eu3+ and Tb3+ ions were prepared by high temperature solid state reaction in air or reducing atmosphere. The luminescence characteristics of the prepared phosphors were investigated. While in the samples prepared in air, Eu3+ emission was found to be dominant over Tb3+ emission, in the samples prepared in reducing atmosphere, intense Eu2+ emission at 448 nm was found to be predominant over narrow Tb3+ emission. Luminescence studies showed that Eu3+ ions occupy asymmetric sites in Zn2SiO4 lattice. The intense f-f absorption peak of Eu3+ at 395 nm observed in these phosphors suggests their potential as red emitting phosphors for near ultra-violet light emitting diodes.  相似文献   

7.
Ba2+-doped Sr2SiO4:Eu2+ phosphors were synthesized with the high-temperature solid-state reaction technique. The experimental results, summarized in the successful production of a single-phase powder with fine microstructure of spherical particles with smooth surface, suggest that Ba2+-doping favors the stabilization of α′-Sr2SiO4. Rietveld refinement of X-ray diffractograms suggests that Ba2+ and Eu2+ ions occupy the sites of Sr2+ in the lattice of α′-Sr2SiO4. The produced phosphors show two intense emission bands at green and yellow regions of spectrum, originated from Eu2+ ions accommodated at two different sites in the host crystal, whose peaks depend on the concentrations of Ba2+ and Eu2+. Intense and broad excitation spectra extend from ultraviolet to the blue region.  相似文献   

8.
Eu2+ and Mn2+ co-doped Ca8Zn(SiO4)4Cl2 phosphors have been synthesized by a high temperature solid state reaction. Energy transfer from Eu2+ to Mn2+ is observed. The emission spectra of the phosphors show a green band at 505 nm of Eu2+ and a yellow band at 550 nm of Mn2+. The excitation spectra corresponding to 4f7-4f65d transition of Eu2+ cover the spectral range of 370-470 nm, well matching UV and/or blue LEDs. The shortening of fluorescent lifetimes of Eu2+ followed by simultaneous increase of fluorescent intensity of Mn2+ with increasing Mn2+ concentrations is studied based on energy transfer. Upon blue light excitation the present phosphor can emit intense green/yellow in comparison with other chlorosilicate phosphors such as Eu2+ and Mn2+ co-doped Ca8Mg(SiO4)4Cl2 and Ca3SiO4Cl2, demonstrating a potential application in phosphor converted white LEDs.  相似文献   

9.
A yellow phosphor, Sr3SiO5:Eu2+, was synthesized by a high temperature solid-state method. Sr3SiO5:Eu2+ exhibits a single yellow emission under the blue radiation excitation. However, Sr3SiO5:Eu2+ shows a two-peak emission under the ultraviolet radiation excitation when Eu2+ doping content is less than 0.01 mol. Moreover, the blue emission disappears and the yellow emission reaches the peak value when Eu2+ doping content is 0.01 mol. Namely, the energy transfer takes place between the Eu2+ activators, which is located at two different crystallographic sites in the Sr3SiO5. And the energy transfer mechanism is the dipole-dipole interaction.  相似文献   

10.
采用高温固相法制备了Ca2SiO4:Dy3+发光材料.在365nm紫外光激发下,测得Ca2SiO4:Dy3+材料的发射光谱为一多峰宽谱,主峰分别位于486nm,575nm和665nm处;监测575nm发射峰,测得材料的激发光谱为一多峰宽谱,主峰分别位于331nm,361nm,371nm,397nm,435nm,461nm和478nm处.研究了Dy3+掺杂浓度对Ca2SiO4:Dy3+材料发射光谱及发光强度的影响,结果显示,随Dy3+浓度的增大,黄、蓝发射峰强度比(Y/B)逐渐增大,利用Judd-Ofelt理论解释了其原因;随Dy3+浓度的增大,Ca2SiO4:Dy3+材料发光强度先增大,在Dy3+浓度为4 mol%时到达峰值,而后减小,根据Dexter理论其浓度猝灭机理为电偶极-电偶极相互作用.研究了电荷补偿剂Li+,Na+和K+对Ca2SiO4:Dy3+材料发射光谱的影响,结果显示,不同电荷补偿剂下,随电荷补偿剂掺杂浓度的增大,Ca2SiO4:Dy3+材料发射光谱强度的演化趋势相同,即Ca2SiO4:Dy3+材料发射峰强度先增大后减小,但不同电荷补偿剂下,材料发射峰强度最大处对应的补偿剂浓度不同,对应Li+,Na+和K+时,浓度分别为4mol%,4mol%和3mol%. 关键词: 白光LED 2SiO4:Dy3+')" href="#">Ca2SiO4:Dy3+ 发光特性 电荷补偿  相似文献   

11.
Eu2+激活的Ca3SiO5绿色荧光粉的制备和发光特性研究   总被引:3,自引:0,他引:3       下载免费PDF全文
杨志平  刘玉峰 《物理学报》2006,55(9):4946-4950
研究了Eu2+激活的绿色发光材料Ca3SiO5的制备条件和发光性质. Eu2+中心形成主峰值为501 nm和次峰值为570 nm的特征宽带,两峰值叠加形成发射峰值为502nm的绿色发射光谱带. 利用这些光谱结果和Van Uitert 经验公式,确认Ca3SiO5:Eu2+中存在两种性质有差异的Eu2+发光中心,它们分别占据基质中八配位的Ca2+(Ⅰ)格位和四配位的Ca2+(Ⅱ)格位. 其激发光谱分布在250—450 nm的波长范围,峰值位于375 nm处,可以被InGaN管芯产生的350—410 nm辐射有效激发. 关键词: 发光 荧光粉 绿色荧光粉 3SiO5')" href="#">Ca3SiO5 2+')" href="#">Eu2+  相似文献   

12.
The temperature dependence of emission spectra of alkaline earth ortho-silicates M2SiO4 (M=Ca, Sr, Ba) doped with Eu2+ ions is investigated. Two emission bands of Sr2SiO4:Eu2+ show the normal redshift with broadening bandwidth and decreasing emission intensity as an increase in temperature. On the other hand, emission bands of Ca2SiO4:Eu2+ and Ba2SiO4:Eu2+ show the anomalous blueshift with increasing temperature. For Ca2SiO4:Eu2+ and Ba2SiO4:Eu2+, the temperature dependence of the emission color can be described in terms of back tunneling from the excited state of low-energy emission band to the excited state of high-energy emission band in the configuration coordinate diagram. Our phosphors have a promising potential as phosphors for green or greenish white-light-emitting diode pumped by ultraviolet chip.  相似文献   

13.
This paper reports the preparation of long persistent Sr2Al2SiO7:Eu2+ and Sr2Al2SiO7:Eu2+, Dy3+ phosphors and the comparison of their photoluminescent properties. The silicate phosphors prepared by solid-state reaction routine showed a broad blue emission peaking at 484 nm when activated by UV illumination. Such a bluish-green emission can be attributed to the intrinsic 4f-5d transitions of Eu2+. After the UV source was switched off, long persistent phosphorescence could be observed by naked eyes for both samples in darkness. Afterglow measurements revealed that Eu/Dy codoped phosphor possesses better afterglow properties than the Eu single doped one, since the maximum lifetime (τmax=99 s) of the photons calculated from the decay profile is much larger than that of the Eu single doped phosphor (τmax=82 s). TSL results suggested that the difference in afterglow properties was caused by the difference in the electron traps within the crystal lattice. For Eu/Dy codoped phosphor, the doping of Dy ions produced electron traps with trap depth of 0.52 eV, which is suitable and therefore leads to good persistence. However, in the case of Eu single doped phosphor, the trap depth is 0.88 eV, which is really too deep an energy barrier to overcome, and therefore a poor persistence was observed in the experiment.  相似文献   

14.
用高温固相法合成了Eu2+,Mn2+共激活的Ca2SiO3Cl2高亮度白色发光材料,并对其发光性质进行了研究. 该荧光粉在近紫外光激发下发出强的白色荧光,Eu2+中心形成峰值为419 nm和498 nm的特征宽带,通过Eu2+中心向Mn2+中心的能量传递导致了峰值为578 nm的发射,三个谱带叠加从而在单一基质中得到了白光. 激发光谱均分布在250—415 nm的波长范围,红绿蓝三个发射带的激发谱峰值分别位于385 nm,412 nm,370 nm和396 nm处,可以被InGaN管芯产生的紫外辐射有效激发. Ca2SiO3Cl2:Eu2+,Mn2+是一种很有前途的单一基质白光LED荧光粉.  相似文献   

15.
In this research we prepared Zn2SiO4:Eu3+ phosphor nanopowders using a combination of sol-gel and combustion synthesis with the aim to examine the influence of synthesis conditions on the optical properties of the phosphor. As combustion fuels we used polyethylene glycol (PEG) with different average molecular weights, and the combustion was performed in two ways—in a microwave oven and a conventional furnace. Optical properties were examined by photoluminescence spectroscopy and spectra of all samples showed intense red emission, typical for f-f electronic transitions of the Eu3+ ions. Emission decays exhibited classical one exponential behavior at longer times and nonlinear nature at short times, with average lifetimes varied from 0.49 to 0.71 ms between samples. Judd-Ofelt theory was applied to experimental data for the quantitative determination of optical parameters such as Ω2,4 Judd-Ofelt parameters, radiative and nonradiative transition rates and emission quantum efficiency. Calculated parameters vary moderately between samples prepared with different PEGs and combusted in different manner.  相似文献   

16.
Tb3+- or Eu3+-doped magnesium silicate phosphors were prepared for the first time by using a novel approach, combined sol-gel-microwave heating. X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric analysis (TGA) and photoluminescence analyses were used to characterize the phosphors. XRD confirmed a forsterite lattice of Mg2SiO4 for the phosphors. TEM observation indicated that the phosphors have a spherical-like shape with little aggregation and the particle size is about 50 nm, and the small size is favorable to the potential application in field emission displays. The luminescent colors of Mg2SiO4:Tb3+ and Mg2SiO4:Eu3+ phosphors are green and red respectively, furthermore the luminescent intensities of them are relatively higher than the traditional Zn2SiO4:Tb3+ and Zn2SiO4:Eu3+ phosphors. In addition, Eu3+ ion emissions as a structural probe suggest that the rare earth ions replace the Mg2+ ions in the site of M2 (Cs) in the forsterite lattice of Mg2SiO4.  相似文献   

17.
Electronic energy relaxation and decay dynamics of Eu3+ in Zn2SiO4:Eu3+ phosphors display evidence of intra-ion energy transfer from the 5D1 to the 5D0 manifold. The energy transfer timescale does not depend on Eu3+ concentration, or the addition of Mn2+ as a co-dopant and is estimated to be about 11 μs in Zn2SiO4. Evidence for intra-ion Eu3+ electronic energy transfer has also been observed in Eu-doped MgS as well as Eu3+ encapsulated in zeolite-Y. The energy transfer timescale in these other materials is shorter than in Zn2SiO4, most likely due to differences in Eu3+ surroundings or site symmetry.  相似文献   

18.
A novel red-emitting phosphor CaSrAl2SiO7:Eu3+ was firstly synthesized through the high temperature solid state reaction at 1300 °C. The structure, diffuse reflection spectra, photoluminescence spectra, color-coordinate parameters and quantum efficiencies (QE) of phosphors were investigated. The obtained CaSrAl2SiO7:Eu3+ phosphors have the same structure with that of the Ca2Al2SiO7 and Sr2Al2SiO7 phosphor, which have the melilite structure. Optical properties were studied as a function of Eu3+ concentration x, when x>0.14, the intensity of absorption of the f–f transitions of Eu3+ at 393 nm is stronger than that of the broad charge transfer transition band (CTB) around 254 nm, and which matches well with the output lights of NUV–LEDs, whereas, the concentration of Eu3+x≤0.14, the absorption of 393 nm is weaker than that of CTB. The underlying reason of Eu3+ concentration on their luminescent properties was investigated and discussed in detail. As a result, comparing with the commercial red phosphor Y2O2S:Eu3+, the CaSrAl2SiO7:xEu3+ (x>0.14) phosphor exhibited excellent color purity and much higher brightness and could be considered as promising red phosphors for NUV–LEDs.  相似文献   

19.
A novel deep-blue phosphor, Ba1.2Ca0.8SiO4:Ce3+, has been developed for white-light-emitting diodes. The phosphor exhibits two absorption bands at 280 and 325 nm, and an intense deep-blue emission peaking at 400 nm. With increasing Ce/Li concentrations, the lattice expands, and the emission peak is blueshifted. This correlation is explained in terms of the crystal field effect and the configurational coordinate diagram. This phosphor shows much higher thermal quenching temperature (225 °C) due to a weak electron-phonon interaction. Thus, it can be used as a sensitizer phosphor to excite other green or red phosphors, or a promising deep-blue phosphor for white-light-emitting diodes.  相似文献   

20.
Jidi Liu  Xue Yu  Jie Li 《Journal of luminescence》2010,130(11):2171-2174
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号