共查询到20条相似文献,搜索用时 15 毫秒
1.
Hom Nath Luitel Toshio Torikai Rumi Chand Kazuhiro Nanoka 《Applied Surface Science》2010,256(8):2347-1893
A novel and efficient method of providing moisture resistance of inorganic particles such as divalent europium activated strontium aluminate phosphors (Sr4Al14O25:Eu2+/Dy3+) was developed by firing the phosphor in the presence of appropriate amount of ammonium fluoride at a temperature of 600-700 °C. Scanning electron microscopy, X-ray diffraction, FT-IR, EDAX and Photoluminescence measurements were carried out to characterize the uncoated and coated samples. The pH measurements were carried out for the water resistivity measurements. The phosphor particles became coated with a moisture-impervious thin coating that did not suppress the luminescence of the phosphor and can withstand complete immersion in water for long periods of time, showing very high water resistivity. 相似文献
2.
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
3.
A coating method with precipitating process was developed to reduce the particle size and to improve the particle dispersion of Y3Al5O12:Tb3+ phosphor prepared by sol-gel method. The particle morphology was observed by using SEM and TEM; and the particle size and its dispersion was measured by using laser scattering technique. Several coating materials were tested. Among them, Al2(SiO3)3 coating not only reduced the particle size from several micrometers to ∼1 μm and improved the particle dispersion, but also well kept luminescent intensities and improved the duration of the phosphor under the bombardment of cathode ray. The mechanism of the particle size reduction was proposed. 相似文献
4.
Haoyi Wu Guifang Ju Li Chen Xiaojuan Wang Zhongfu Yang 《Journal of luminescence》2011,131(12):2441-2445
The Ca2Al2SiO7 samples doped with Ce3+ and Eu2+ are synthesized via a high temperature solid-state reaction. Ca2Al2SiO7: Ce3+ emits a strong UV-violet emission while Ca2Al2SiO7: Eu2+ emits a blue-green emission. The Stokes shift of the latter is greater due to a stronger crystal repulsion from ligands to Eu2+ ions. Ca2Al2SiO7: Ce3+ exhibits a stronger initial intensity and longer duration of afterglow due to the higher liberated probability of the trapped carriers. The thermoluminescence curves reveal that at least three traps exist in the phosphors. Ca2+ vacancies may enhance the electron trapping and then lead to a stronger afterglow. A possible explanation will be provided. 相似文献
5.
Xianqing Piao Ken-ichi Machida Takashi Horikawa Bonggoo Yun 《Journal of luminescence》2010,130(1):8-12
A novel synthesis method was developed for the efficient red phosphor, Eu2+-activated Sr2Si5N8, by employing the strontium acetate as both the reducing agent and strontium source. The phase purity of final product was strongly dependent on the heating rate of the precursors. Sr2Si5N8:Eu2+ (2 at%) phosphor presented a broadband excitation spectrum in the range 300–500 nm, matching well with the blue emission (400/460 nm) of current InGaN light-emitting diodes (LEDs). The red emission peaking at 619 nm gave the relatively high (about 155%) intensity compared with the Y3Al5O12 (YAG) (P46-Y3) standard phosphor. In addition, the saturated chromatic coordinates (0.638, 0.359) allowed it a promising candidate as a red phosphor in white LEDs application for illumination or display. 相似文献
6.
研究了Er1.0P5O14铒非晶玻璃的红外量子剪裁现象. 从吸收谱和激发光谱的计算比较中肯定了Er1.0P5O14非晶 玻璃的1537.0 nm红外荧光为多光子量子剪裁荧光. 从Er1.0P5O14非晶玻璃的可见和红外荧光发射光谱中发现激发2H11/2, 4G11/2和4G9/2能级所导致的4I13/2→4I15/2量子剪裁红外荧光很强;基于自发辐射速率、无辐射弛豫速率和能量传递速率等参数的计算,对其量子剪裁机理进行了分析.发现起源于基态的强下转换能量传递{2H11/2→4I9/2,4I15/2→4I13/2},{4G11/2→4I13/2, 4I15/2→2H11/2},{4G9/2→4F7/2,4I15/2→4I13/2}和{4G9/2→4I13/2, 4I15/2→2H11/2}是导致Er1.0P5O14非晶玻璃具有强的三光子和四光子量子剪裁红外荧光的原因.研究结果对改善太阳能电池效率有一定意义. 相似文献
7.
Li-Ming Shao 《Journal of luminescence》2011,131(6):1216-1221
The phosphors in the system Y3−xAl5-yO12:xCe3+,yCr3+ were synthesized by solid-state reactions and their photoluminescence properties were investigated. These phosphors have absorption in the visible light region and give luminescence in the far-red region (∼688 nm), which are suitable for the application in the device of luminescent solar concentrator (LSC). In these phosphors, Ce3+ located at Y3+ site can effectively transfer its absorbed energy to Cr3+ at Al3+ site. 相似文献
8.
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
9.
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
10.
Simas Sakirzanovas Artūras Katelnikovas Danuta Dutczak 《Journal of luminescence》2011,131(11):2255-2262
Complete and partial samarium reduction was achieved under strong reducing atmosphere by solid-state and combustion synthesis of Sr3.96Sm0.04Al14O25. Dependence of different fluxing agents on the formation of various strontium aluminates was examined. The samples were investigated by X-ray powder diffraction, temperature dependent luminescence decay and photoluminescence measurements. Excitation with UV radiation resulted in sharp and well resolved emission lines of samarium ions. Distinct temperature behavior for Sm2+ and Sm3+ were detected in the range of 100-500 K. Estimated emission thermal quenching values (TQ1/2) for divalent samarium were approximately 270 K while for trivalent state around 660 K. Measured luminescence decay values of Sm2+ are substantially lower than for Sm3+,≈1.7 and ≈2.7 ms, respectively. The spectral feature of Sm2+ emission spectrum indicates that dopant occupies low symmetry site in Sr4Al14O25 compound. 相似文献
11.
Ultrafine particles of BaMgAl10O17:Eu2+ (BAM) phosphor were synthesized by a solid-state combustion reaction in a powder bed of 0.9BaCO3+MgO+5Al2O3+0.05Eu2O3+k(KClO3+1.5C) composition. A large exothermic reaction of the mixture (KClO3+1.5C) leads to a self-sustaining combustion mode. Under optimized combustion conditions, the product consisted of BAM powder and KCl was obtained. BAM ultrafine particles resulting from the combustion process were easily obtained by simply washing the salt by-product with water. Combustion-processed BAM phosphor shows a homogeneous grain size of 100-500 nm, good dispersity, regular morphology, and improved luminescence properties. 相似文献
12.
H. Chudo H. Sakai S. Kambe Y. Homma Y. Haga T.D. Matsuda H. Yasuoka 《Physica B: Condensed Matter》2009,404(19):3216-3219
We present 27Al NMR studies for a single crystal of the Np-based superconductor NpPd5Al2. We have observed a five-line 27Al NMR spectrum with a center line and four satellite lines separated by first-order nuclear quadrupole splittings. The Knight shift clearly drops below Tc. The temperature dependence of the 27Al nuclear spin-lattice relaxation rate shows no coherence peak below Tc, indicating that NpPd5Al2 is an unconventional superconductor with an anisotropic gap. The analysis of the present NMR data provides evidence for strong-coupling d-wave superconductivity in NpPd5Al2. 相似文献
13.
The pseudo-potential plane-wave method using the generalized gradient approximation (GGA) within the framework of the density functional theory is applied to study the structural and thermodynamic properties of Y 3Al5O12. The lattice constants and bulk modulus are calculated. They keep in good agreement with other theoretical data and experimental results. The quasi-harmonic Debye model, in which the phononic effects are considered, is applied to the study of the thermodynamic properties. The temperature effect on the structural parameters, bulk modulus, thermal expansion coefficient, specific heats and Debye temperatures in the whole range from 0 to 20 GPa and temperature range from 0 to 1500 K. 相似文献
14.
采用新型超声喷雾共沉淀法技术,以Lu2O3、Eu2O3、Al(NO3)3·9H2O为原料,制备了不同浓度Eu3+离子掺杂的Lu3Al5O12纳米粉体.用X射线粉末衍射表征了获得纳米粉体的相,用扫描电镜观察了纳米粒子的形貌.测定了粉体的激发光谱、7F0-5D2声子边带谱与发射光谱.研究了不同高温烧结温度与Eu3+掺杂浓度对纳米粒子的发光强度与粒子形貌的影响规律.研究表明,当烧结温度高于900 ℃时,粉体发光强度明显增强,并且随着煅烧温度的增加,发光强度有所增强.Eu3+离子的最佳掺杂浓度为5~7 mol%.根据稀土离子Eu3+光学跃起矩阵元的特点,从发射光谱获得Eu3+光学跃起的J-O参量Ω2与Ω4.在Eu3+掺杂浓度均为5 mol%时,其强度参量达最小,电-声子耦合最强.然后随着掺杂浓度的进一步提高,强度参量略有增加,电-声子耦合减弱.说明Eu-O键强增加,共价性增强,Eu3+的局域环境对称性降低.Ω2值低于Eu3+在玻璃与晶体基质中的情况,这是由于纳米粒子中存在着大量的缺陷以及晶体的结构畸变导致纳米粒子的对称性下降所致. 相似文献
15.
Long afterglow Sr3MgSi2O8: Eu, Dy phosphor with high brightness was prepared by sintering at high temperature and weak reductive atmosphere. The luminescent properties of this photoluminescent pigment were studied systematically by investigating concentration effects. The analytical results indicated that the main emission peaks appear at 482 nm. The excitation and emission spectra of this phosphor show that both of them are broadband. This is ascribed to the 4f7→4f65d1 transition of Eu2+ in the pigment matrix, which is in good agreement with the calculated value of 470 nm, and implies that luminescent centers Eu2+ occupy the deca-coordinated Sr2+ sites with the host of Sr3MgSi2O8. 相似文献
16.
Zhongfei Mu Yihua Hu Haoyi WuChujun Fu Fengwen Kang 《Physica B: Condensed Matter》2011,406(4):864-868
A series of phosphors with the composition Y3MnxAl5−2xSixO12 (x=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6) was prepared through solid state reactions. X-ray powder diffraction analysis of samples shows that when co-doping content does not exceed 16% of Al3+, equimolar co-doping of Mn2+ and Si4+ does not change the garnet structure of phosphors, but makes the interplanar distance to decrease a certain extent. However, if the co-doping content exceeds 16%, new phases will form in the samples. The excitation and emission spectra of samples show that Mn2+ in Y3MnxAl5−2xSixO12 emits broadband orange light (peak wavelength varies from 586 to 593 nm). With an increment in co-doping content, the emission intensity of the phosphors increases when the value of x is lower than 0.1 while it decreases when it is higher than 0.1 and the emission peak moves to a longer wavelength. 相似文献
17.
A series of phosphors with the composition Y3−xMnxAl5−xSixO12 (x=0, 0.025, 0.050, 0.075, 0.150, 0.225, 0.300) were prepared with solid state reactions. The X-ray powder diffraction analysis of samples shows that the substitution of Mn2+ and Si4+ does not change the garnet structure of phosphors, but makes the interplanar distance decrease to a certain extent. The emission spectra show that Mn2+ in Y3Al5O12 emits yellow-orange light in a broad band. With the increment of substitution content, the emission intensity of the phosphors increases firstly then decreases subsequently, and the emission peak moves to longer wavelength. Afterglow spectra and decay curves show that all the Mn2+ and Si4+ co-doped samples emit yellow-orange light with long afterglow after the irradiation of ultraviolet light. The longest afterglow time is 18 min. Thermoluminescence measurement shows that there exist two kinds of traps with different depth of energy level and their depth decreases with the increment of substitution content. 相似文献
18.
Low thermal quenching and high-efficiency Ca3Sc2Si3O12:Ce3+ (CSSO:Ce3+) phosphors with co-doping Tb3+ ion were prepared by a solid state method and the properties of these phosphors were investigated. The results showed that co-doping of Tb3+ not only enhances the photoluminescence remarkably and decreases the thermal quenching of the phosphor, but also heightens the performances of the LEDs fabricated with the phosphor. A high-efficiency and low color temperature white LED was fabricated with the prepared CSSO:1%Ce3+, 0.5%Tb3+ and a red phosphor, indicating that CSSO:1%Ce3+,0.5%Tb3+ phosphor is a suitable green phosphor for the fabrication of high-efficiency white LEDs. 相似文献
19.
Vengala Rao Bandi Kiwan Jang Sang-Su Kim Yong-Ill Lee Taekwon Song 《Journal of luminescence》2011,131(11):2414-2418
CaZrSi2O7 (CZS), a modification of the thortveitite family, was prepared as a polycrystalline powder material by the conventional solid-state reaction method. Structural, thermal and photoluminescence (PL) properties of the prepared material were investigated in order to evaluate its potentiality. XRD patterns confirm the monoclinic phase of CaZrSi2O7: Eu2+ phosphors.. Emissions arising from transitions between the 5d and 4f orbital gaps of Eu2+ are manifested in the broadband excitation and emission spectra with major peaks at 363 and 512 nm, respectively. The excitation wavelength matches well with that of the emission of the ultraviolet-light emitting diode (UV-LED). Concentration quenching occurs when the Eu2+ concentration is beyond 0.05 and the dipole-dipole interaction was the reason for the corresponding quenching mechanism. The temperature dependence of emission intensity of CZS: Eu2+ phosphor was investigated and it showed better thermal stability than the standard YAG: Ce3+ phosphor. 相似文献
20.
Nanocrystalline Y3Al5O12: Ce3+/Tb3+ (average crystalline size 30 nm) phosphor layers were coated on non-aggregated, monodisperse and spherical SiO2 particles by the sol-gel method, resulting in the formation of core-shell structured SiO2@Y3Al5O12:Ce3+/Tb3+ particles. X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, photoluminescence,
cathodoluminescence spectra, as well as lifetimes were utilized to characterize the core-shell structured SiO2@Y3Al5O12:Ce3+/Tb3+ phosphor particles. The obtained core-shell structured phosphors consist of well-dispersed submicron spherical particles
with a narrow size distribution. The thickness of the Y3Al5O12:Ce3+/Tb3+ shells on the SiO2 cores (average size about 500 nm, crystalline size about 30 nm) could be easily tailored by varying the number of deposition
cycles (100 nm for four deposition cycles). Under the excitation of ultraviolet and low-voltage electron beams (1–3 kV), the
core-shell SiO2@Y3Al5O12:Ce3+/Tb3+ particles show strong yellow-green and green emission corresponding to the 5d–4f emission of Ce3+ and 5D4–7F
J
(J = 6, 5, 4, 3) emission of Tb3+, respectively. These phosphors may have potential application in field emission displays. 相似文献