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1.
Himansu S. Tripathi 《Materials Research Bulletin》2007,42(2):197-202
Cerium-doped lutetium pyrosilicate (Lu2Si2O7:Ce) powder was synthesized by solid state reaction of Lu2O3 and SiO2. Stoichiometric mixtures of the starting materials were heat treated at various different temperatures and their phase contents were measured by XRD technique. It was found that the first step in the formation of Lu2Si2O7 (LPS) is the appearance of Lu2SiO5 (LSO). This takes place at 1100 °C, fully 300 °C below the first appearance of LPS. Between 1400 and 1500 °C both LSO and LPS coexist in the calcined batch, but by 1550 °C all LSO is completely converted to LPS. LPS formation temperature does not have appreciable effect on the density of the hot pressed samples. Hot pressed samples obtained from powder synthesized at 1650 °C are nearly transparent, although the particle size of the starting powder is higher than that of the powder formed at lower temperatures. 相似文献
2.
Mullite have been actively surveyed, but as luminescent host materials, lanthanide doped mullite receive little attention. In this work, terbium and cerium co-doped mullite nanoparticles have been synthesized by co-precipitation process. These as-prepared mullite nanocrystals were characterized by transmission electron microscopy. The results showed that these nanoparticles are roughly spherical in shape and vary in size from 30 to 45 nm. The phase structures of these nanoparticles were investigated by X-ray diffraction. The results indicated that these nanoparticles crystallized well, and the peak positions and intensities agree well with the data for bulk mullite. Their fluorescence properties have been explored in detail and the resulting Al6Si2O13: 8%Tb,0.1%Ce nanoparticles showed the typical emission bands centered at 490, 542 and 590 nm. 相似文献
3.
Xin Xu Chao Cai Luyuan Hao Yachong Wang Qunxiang Li 《Materials Chemistry and Physics》2009,118(2-3):270-272
Cerium-doped Lu4Si2O7N2 green phosphors were synthesized by a high-temperature solid-state reaction method under nitrogen atmosphere. Compared with Ce-doped Y4Si2O7N2 phosphors, Ce-doped Lu4Si2O7N2 phosphors showed longer wavelengths of both excitation and emission, lower Stokes shift, and much stronger emission intensity. Based on the first-principles calculations of the two phosphors, the strong emission intensity originates from the large density of states. At last, the effects of Ce3+ concentration on photoluminescence were also examined. 相似文献
4.
Jingmei Ma Feng Ye Limeng Liu Haijiao Zhang 《Materials Science and Engineering: A》2009,520(1-2):158-161
Dense short silicon carbide (SiCsf) and carbon fibers (Csf) reinforced BaAl2Si2O8 (BAS) glass-ceramic composites with silicon nitride were fabricated by hot-pressing technique. The phase characterization, microstructure, mechanical properties and fracture behavior of the composites were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and three-point bending tests. The results showed that short silicon carbide and carbon fibers disperse homogeneously in BAS matrix, and had good chemical compatibility with the glass-ceramic matrix. The addition of Si3N4 could successfully eliminate the microcracks in the BAS matrix induced by the thermal mismatch between the fiber and matrix. Both the added short fibers could effectively reinforce the BAS glass-ceramic by the associated toughening mechanisms such as crack deflection, fiber bridging and pullout effects. 相似文献
5.
6.
《Optical Materials》2013,35(12):1969-1974
Single crystalline films (SCFs) of undoped and Ce3+ doped Y2SiO5 (YSO) and Lu2SiO5 (LSO) orthosilicates were crystallized for the first time by liquid phase epitaxy method onto undoped YSO substrates from melt-solution based on PbO–B2O3 flux. The scintillation and luminescent properties of YSO:Ce and LSO:Ce SCFs were compared with the properties of bulk single crystal counterparts. We show that the peculiarities of luminescent properties of YSO:Ce and LSO:Ce SCFs in comparison with the crystal analogues are caused by the different distribution of Ce3+ ions over Y1/Lu1 and Y2/Lu2 positions of YSO and LSO host and strong influence of Pb2+ flux-related impurity on luminescent properties of Ce3+ ions. 相似文献
7.
In this study, various lanthanide and mixed lanthanide oxides (Ln2O3 with Ln = La, Lu, Lu0.5Gd0.5) powders have been synthesized by a coprecipitation method. The luminescence properties and/or the quenching mechanisms of different dopants (europium, cerium, praseodymium) have been studied. Luminescence mechanisms of Ce:Ln2O3 and Pr:Ln2O3, are closely related to the 5d and 4f energy levels positions of the dopant versus materials bandgap and crossing effect between dopant energy levels. Energy level positions have been analyzed through optical spectroscopy and their effect on the luminescence is presented. Eu:Lu2O3 and Eu:LuGdO3 have also been prepared as transparent ceramics and radioluminescence properties are presented. 相似文献
8.
Hongtao Jiang Xiufeng Wang Gang Hao Lili Wang 《Journal of Materials Science: Materials in Electronics》2013,24(2):814-818
In this paper, Bismuth silicate (Bi4Si3O12, BSO) powders were prepared by reaction in molten salts (NaCl and KCl) using Bi2O3 and SiO2 powders as raw materials. The effects of salt contents and excessive contents of Bi2O3 and SiO2 were characterized by X-ray diffraction and scanning electron microscopy. The properties of Bi4Si3O12 powders were analyzed via fluorescence spectroscopy. Forming mechanism of platelets was discussed. The experimental results suggest that Bi4Si3O12 powders are produced at 780 °C for 4 h with 40 wt% salts and 5 wt% excessive content of Bi2O3. The peaks of excitation spectrum and emission spectrum for BSO powders are separately located at 266 and 457.6 nm. Compared with crystal materials, the excitation spectrum and emission spectrum of Bi4Si3O12 powders indicate blue shift. Interface reacting mechanism can be used to explain the coarsening process of bismuth silicate platelets produced in molten salt synthesis. In addition, dissolution–precipitation mechanism also plays an important role in the synthesis of bismuth silicate platelets. 相似文献
9.
The results of formation of the high density effective scintillation ceramics consisting of two compounds of the cubic symmetry, LuAG:Ce and Lu2O3 (LuAG:Ce + Lu2O3), are described. Powders of a novel material LuAG:Ce + Lu2O3 were synthesized by co-precipitation method. The introduction of Lu2O3 into LuAG:Ce was shown to increase the density of the ceramics obtained and modify its scintillation properties. 相似文献
10.
Hyung Tae Kim Jung Hyun Kim Jung-Kul Lee Yun Chan Kang 《Materials Research Bulletin》2012,47(6):1428-1431
Green light-emitting Lu2.985Al5O12:Ce0.015 (LuAG:Ce) phosphor powders are prepared by spray pyrolysis. The only crystallized phase in the precursor powders and post-treated powders at temperatures below 800 °C is Lu2O3 and the other components are amorphous. Phase pure cubic garnet LuAG:Ce phosphor powders are obtained by post-treatment at 1000 °C. Phosphor powders post-treated at temperatures below 1400 °C retain the spherical shape of the precursor powders. The mean crystallite sizes of phosphor powders post-treated at 1200, 1400, and 1500 °C are 30, 46, and 54 nm, respectively. The excitation spectra contain two bands: a weak band with the maximum peak at 345 nm and a strong broad band in the spectral range from 400 to 490 nm with the maximum peak at 455 nm. The LuAG:Ce phosphor powders have broad emission spectra between 480 and 600 nm, with the maximum peak intensity located at 507 nm. The photoluminescence intensity of the phosphor powders post-treated at 1400 °C is 84.2% of that of the powders post-treated at 1500 °C. 相似文献
11.
RExLu2-x
O3:Eu3+ (RE = Y, Gd) nanophosphors with x = 0.4, 1.0, and 1.6 were synthesized using rare-earth salicylate coordination polymers as precursors for the luminescent species RExLu2-x
O3:Eu3+ (RE = Y, Gd) composed of polyethylene glycol both as a dispersing medium and fuel. Their particle sizes were around 100 nm as determined by scanning electron microscopy and x-ray diffraction.__________From Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 706–710.Original English Text Copyright © 2005 by Zhou, Yan.This article was submitted by the authors in English. 相似文献
12.
Zhiguo Xia Haiyan Du Jiayue Sun Daimei Chen Xuefeng Wang 《Materials Chemistry and Physics》2010,119(1-2):7-10
A blue-emitting Ca2B5O9Br:Eu2+ phosphor for white light-emitting diodes was synthesized via a microwave calcination route. The phosphor powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer, respectively. The obtained results revealed that the Ca2B5O9Br:Eu2+ phosphor prepared by the microwave calcination route possessed a rod-like morphology with the single phase orthorhombic structure. Based on the photoluminescence analysis, it was found that Ca2B5O9Br:Eu2+ phosphor exhibited a broad excitation band chiefly in the near ultraviolet region (270–420 nm) and a blue broad emission band of main peak at 452 nm under the strongest excitation of 411 nm. Further investigation on concentration-dependent emission spectra indicated that Ca2B5O9Br:0.03Eu2+ phosphor exhibited the strongest luminescent intensity, and the concentration quenching for the two Eu-site emission centers was caused by dipole–dipole interactions. 相似文献
13.
The paper is dedicated to study the luminescent and scintillation properties of the Al2O3:Ce single crystalline films (SCF) grown by LPE method onto saphire substrates from PbO based flux. The structural quality of SCF samples was investigated by XRD method. For characterization of luminescent properties of Al2O3:Ce SCFs the cathodoluminescence spectra, scintillation light yield (LY) and decay kinetics under excitation by α-particles of Pu239 source were used. We have found that the scintillation LY of Al2O3:Ce SCF samples is relatively large and can reach up to 50% of the value realized in the reference YAG:Ce SCF. Using the synchrotron radiation excitation in the 3.7–25 eV range at 10 K we have also determined the basic parameters of the Ce3+ luminescence in Al2O3 host. 相似文献
14.
通过浮区法制备得到LPS:0.5%Ce单晶样品, 并对其包裹体、开裂、闪烁和光学性能进行了研究,获得了晶体的电子探针谱、透过谱、77~500 K下的紫外激发发射谱、X射线激发发射谱和77~500 K下的衰减时间谱。研究发现晶体中存在解理开裂和热应力开裂, 同时存在两种类型的包裹体, 分别包含[Si3O9]6-、阴离子团和过量的SiO2。由于采用空气为生长气氛, 样品中部分Ce3+被氧化为Ce4+。浮区法LPS:0.5%Ce表现出较高的发光效率, 约为32000 ph/MeV。随着温度的升高, 样品的紫外激发发射谱逐渐向长波方向移动, 发射谱谱线随着温度的升高展宽, 导致自吸收的增加。衰减时间的温度转变点位于450 K, 表明LPS:Ce闪烁晶体适用于高温环境, 是一种性能优异的闪烁晶体。 相似文献
15.
Two series of Lu3Al5O12:Cr3+ and Lu3Al5O12:0.5% Ce3+,Cr3+ luminescent materials were prepared by a sol–gel combustion method. All samples were characterized by powder X-ray diffraction (XRD), infrared (IR) and photoluminescence (PL) measurements. Moreover, luminous efficacies (LE), CIE 1931 colour points, and quantum efficiencies (QE) were calculated and discussed. Luminescence measurements indicated that Ce3+ ions located at Lu3+ site transfers absorbed energy to Cr3+ ions located at Al3+ site. However, with increasing Cr3+ concentration the total light output of Lu3Al5O12:0.5% Ce3+,Cr3+ phosphors decrease. 相似文献
16.
Nathalie Pradal Audrey Potdevin Geneviève Chadeyron Rachid Mahiou 《Materials Research Bulletin》2011,46(4):563-568
Blue-emitting Eu2+-doped barium magnesium aluminate (BaMgAl10O17:Eu2+) for advanced displays and lighting devices was prepared by a microwave induced solution combustion synthesis using urea as combustion fuel and nitrates as oxidizer. Purity control of as-synthesized blue phosphor particles was undertaken by modifying the fuel to oxidizer molar ratio. X-ray diffraction, scanning electron microscopy and photoluminescence were used to investigate powders crystallinity, particles size, morphology and luminescent properties, respectively. Fuel-rich urea reactions preferentially lead to pure phases compared to the powders synthesized with a stoichiometric fuel to oxidizer ratio. In both cases, we produce a nearly pure well-crystallized and nanostructured BaMgAl10O17:Eu2+. Photoluminescence measurements exhibit the characteristic blue emission of Eu2+ under UV light excitation however a weak red emission associated to Eu3+ is also detected. 相似文献
17.
Growth and luminescent properties of Lu2SiO5 and Lu2SiO5:Ce single crystalline films 总被引:1,自引:0,他引:1
Yu. Zorenko M. NiklV. Gorbenko V. SavchynT. Voznyak R. KucerkovaO. Sidletskiy B. GrynyovA. Fedorov 《Optical Materials》2011,33(6):846-852
Single crystalline films (SCF) of Lu2SiO5 (LSO) and Lu2SiO5:Ce (LSO:Ce) silicates with thickness of 2.5-15 μm were crystallized by liquid phase epitaxy method onto undoped LSO substrates from melt-solution based on PbO-B2O3 flux. The scintillation and luminescence properties of LSO:Ce SCF were compared with the properties of LSO:Ce single crystal. The peculiarities of luminescence properties of LSO:Ce SCF in comparison with crystal analog can be due to different distribution of Ce3+ over the Lu1 and Lu2 positions of LSO host and are further influenced by Pb2+ flux-originated contamination. 相似文献
18.
Bobo Yang Jun Zou Mingming Shi Fengchao Wang Yang Li Wenbo Li Lei Yang Yujie Lin 《Journal of Materials Science: Materials in Electronics》2017,28(5):4075-4082
Green Lu2.94?xYxAl5O12: 0.06Ce phosphors were prepared by conventional solid-state reaction. The influence of Y concentration on the photoluminescence (PL), thermal stability and reliability properties of the phosphors were studied. The PL emission bands of Lu2.94?xYxAl5O12: 0.06Ce showed red shift from 520 to 540 nm with increasing Y content (x value) under excited at 450 nm. As the temperature increases from 298 to 473 K, the PL intensity of Lu2.94?xYxAl5O12: 0.06Ce phosphor decreases by 21.72, 11.10, 5.45, 9.01 and 16.30% with x value is 0, 0.2, 0.4, 0.6 and 0.8, respectively. The thermal cycling testing results show that the relative PL intensity of Lu2.94?xYxAl5O12: 0.06Ce phosphor decrease to 86.97, 91.94, 97.22, 95.69 and 92.75% with x value is 0, 0.2, 0.4, 0.6 and 0.8 after storing the phosphors into an ambient condition of 120 °C for 1 h and ?40 °C for 1 h by turns for five times. Reliability test results show that the relative PL intensity of Lu2.94?xYxAl5O12: 0.06Ce phosphor decrease to 90.76, 95.17, 96.54, 93.37 and 91.12% with x value is 0, 0.2, 0.4, 0.6 and 0.8 after the ambient condition of 85 °C/RH 85% for the exposure time of 336 h; The relative PL intensity of Lu2.94?xYxAl5O12: 0.06Ce phosphor decrease to 88.63, 94.24, 95.74, 92.60 and 86.95% with x value is 0, 0.2, 0.4, 0.6 and 0.8 after soaking into boiled water for 3 h. It can be summarized that the appropriate addition of Y could enhance both the thermal stability and reliability of Lu2.94?xYxAl5O12: 0.06Ce phosphors remarkably. 相似文献
19.
Wenzhi Huang Jili Yang Chunjie Wang Binglin Zou Xiangsheng Meng Ying Wang Xueqiang Cao Zhen Wang 《Materials Research Bulletin》2012,47(9):2349-2356
ZrO2–CeO2 mixed oxides were synthesized via sol–gel process. Thermal stability, structure and morphology of samples were investigated by powder X-ray diffraction, FT-Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. In this approach, the solvent composition and Zr/Ce molar ratio have great influences on the structure and morphology of final products. With decreasing water content in the mixed solvent, specific surface area of powders increased and the single tetragonal phase was obtained. Only when the volume ratio of water and ethanol and the Zr/Ce molar ratio were 1:1, tetragonal t″-Zr0.5Ce0.5O2 could be stabilized in powders at temperature as high as 1000 °C. Meanwhile, tetragonal (t′) and (t″) phases coexisted in Zr0.5Ce0.5O2 solid solution without peak splitting after calcination at 1100 °C, further transforming into cubic and tetragonal (t′) phases at 1200 °C. The effective activation energy for Zr0.5Ce0.5O2 nanocrystallite growth during annealing is about 5.24 ± 0.15 kJ/mol. 相似文献
20.
Yinrong Fu Shaoan Zhang Yihua Hu 《Journal of Materials Science: Materials in Electronics》2017,28(7):5262-5269
A series of novel red-emitting Na2Ca3???x Si2O8:xEu3+ phosphors were synthesized by solid state reactions. The phosphors can strongly absorb 395 nm light, and show red emission with a good color purity. The excitation and emission spectra properties of Na2Ca3Si2O8:Eu3+ were characterized. Na2Ca3Si2O8:Eu3+ with self-compensated and alkali metal ions charge compensated approaches (2Ca2+→Eu3+ + M+, M?=?Li+, Na+, K+) have investigated, which found that the red emission of luminescent intensity can be greatly enhanced, and shows superior luminescent property to the commercial Y203S:Eu3+. The present work implies that the efficient charge compensated phosphors are promising candidates as red-emitting phosphor for w-LEDs. 相似文献