由稀土氧化物直接制备无水稀土溴化物

以化学气相传输法制取无水LaBr3、GdBr3和LuBr3。以稀土氧化物为原料,与铝粉及溴直接进行反应,可得到LnBr3和Al2O3的混合物。当铝与溴过量时,铝与溴生成的AlBr3,在高温下形成气态Al2Br6,并与LnBr3反应得到气态配合物,该配合物在低温分解。控制适当的温度梯度场,可实现LnBr3与其他固体分离。产物纯度>99.5%。利用化学气相传输法可获得纯度较高的无水LnBr3。     

化学气相传输法制备无水氯化镥

以化学气相传输法制取无水ＬｕＣｌ３。Ｌｕ２Ｏ３（ｓ）与Ａｌ２Ｃｌ６（ｇ）在３００℃反应生成ＬｕＣｌ３（ｓ）。反应完成后,利用４００～１８０℃的温度梯度场,实现ＬｕＣｌ３（ｓ）的气相传输分离。剩余氯化铝在２００℃用Ｃｌ２－Ｎ２混合载气去除。产物纯度〉９９．９％。     

化学气相传输法分离相邻四元混合轻稀土氧化物

基于稀土氯化物在高温时与KCl生成气态配合物KRECl4的热力学行为差异,将稀土氯化物和KCl按摩尔比1:1混合,另将稀土氧化物、NH4Cl和KCl按RE:N:KCl=1:6:1(RE=La、Ce、Pr、ND)的摩尔比混合,进行化学气相传输反应,研究混合稀土化合物的分离特性.实验结果显示,单一轻稀土氧化物-NH4Cl-KCl传输反应在650℃～800℃的温度范围内稀土沉积量PrCl3＞NdCl3＞LaCl3＞CeCl3.四元相邻混合轻稀土氯化物-KCl传输反应,在不同温度区域内最大分离系数分别为SFLa/Ce(5)=2.51,SFPr/La(5)=3.86,SFNd/La(4)=2.61,SFpr/Ce(5)=9.76,SFNd/ce(4)=4.28,SFNd/Pr(2)=2.50.四元相邻混合轻稀土氧化物-NH4Cl-KCl传输反应,在不同温度区域内最大分离系数分别为SFNdLa/ce(2)=3.01,SFPr/La(6)=3.31,SFNd/La(4)=2.47,SFPr/ce(5)=8.84,SFNd/ce(6)=5.02,SFNd/Pr(2)=2.02.     

Luminescence of Eu^3 ＋ in LnAlO3 （Ln = Gd, Y） under UV and VUV Excitation

Single phases of LnAlO3 : Eu^3 ( Ln = Gd, Y ) were obtained by the process of evaporation of their nitric acid solution, and then pyrolysis of their nitrate salts. On monitoring by 613 nm emission, broad bands at around 270 and 170nm were observed in the excitation spectrum of Gd0.95Eu0.05AlO3. These peaks could be assigned to charge transfer (CT)transitions of Eu^3 -O^2- and Gd^3 -O^2- respectively. All the transitions observed in Gd0.95Eu0.05AlO3 are faithfully reproduced in the Y0.95Eu0.05AlO3, but with an exception of the ^8S7/2→^6I11/2 transition of Gd^3 . The 153 nm broad band could be the CT transition of Y^3 -O^2 - . Accordingly, the efficiency luminescence of (Gd, Y) BO3 : Eu^3 was explained as a result of CT transitions of Gd^3 -O^2- and Y^3 -O^2- under 147 nm excitation. Under VUV excitation, Gd0.95Eu0.05AlO3 exhibits a bright red luminescence with CIE chromaticity coordinates of (0.623, 0. 335) with a PL intensity of 30 of the commercial phosphor (Gd, Y) BO3 : Eu^3 (KX-504A). The PL spectrum of Y0.95Eu0.05AlO3 is similar to that of Gd0.95Eu0.05AlO3. Calculation of the color coordinates gives x = 0. 636, y = 0. 340 with a PL intensity of 50 of the (Gd, Y) BO3 : Eu^3 ( KX-504A) for Y0.95Eu0.05AlO3, and confirms that it has the appearance of pure spectral red, corresponding approximately to 608 nm. It can be concluded that LnAlO3:Eu^3 is a promising red VUV phosphor.     

Stepwise Chlorination-Chemical Vapor Transport Reactions for Bastnaesite Concentrate

Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination-chemical vapor transport reactions mediated by vapor complexes LnAlnC13n 3(Ln = RE elements). The bastnaesite was heated to 800 K and chlorinated between 800- 1300 K with ,C C12 SiClr to remove CO2, SiF4 and high volatile chlorides. At the temperature of 1300 K for 6 h, the resulted RE chlorides were chemically transported and mutual separated with the vapor complexes while CaC12 and BaC12 were remained in the residues. Significantly different CVT characteristics were observed for gradually decreased and wave form temperature gradients.     

Growth of ZnO Single Crystal by Chemical Vapor Transport Method

ZnO crystals were grown by CVT method in closed quartz tube under seeded condition. Carbon was used as a transport agent to enhance the chemical transport of ZnO in the growth process. ZnO single crystals were grown by using GaN/sapphire and GaN/Si wafer as seeds. The property and crystal quality of the ZnO single crystals was studied by photoluminescence spectroscopy and X-ray diffraction technique.     

Metathesis synthesis,characterization, spectral and photoactivity studies of Ln2/3MoO4 (Ln=La,Pr, Nd,Sm, Eu,Gd, Tb,Dy, Er and Y)

Rare earth ortho-oxomolybdates of composition Ln2/3MoO4 (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er and Y) were prepared by metathesis reaction. All these materials were characterized by powder X-ray diffra...     

Enhanced photoluminescence properties of （Y,Bi） BO_3：RE~（3＋） （RE=Eu,Tb） phosphors synthesized at low temperature

Eu3+ or Tb3+ doped Y(1-x)BixBO3 (0.1≤x≤0.4) phosphors were synthesized using the simple solid state method at low temperature from 700 to 870 ℃. The analysis of the X-ray diffraction (XRD) indicated that the system of Y(1-x)BixBO3 (0.1≤x≤0.4) had the same structure as that of YBO3. The excitation spectra, emission spectra and decay lifetimes of all samples were measured in detail. All the samples exhibited characteristic luminescence of Eu3+ or Tb3+. Y0.65Bi0.2Eu0.15BO3 and Y0.8Bi0.1Tb0.1BO3 samples had the...     

Separation of Neighboring REElementsfrom Sm_2O_3Eu_2O_3Gd_2O_3 System by a Stepwise ChlorinationChemical Vapor Transport Reaction

Ａｔｐｒｅｓｅｎｔ，ｒａｒｅｅａｒｔｈｓｅｐａｒａｔｉｏｎａｎｄｐｕｒｉｆｉｃａｔｉｏｎｆｏｒｃｏｍｍｅｒｃｉａｌｕｓｅａｒｅｍａｉｎｌｙｃａｒｒｉｅｄｏｕｔｂｙｓｏｌｖｅｎｔｅｘｔｒａｃｔｉｏｎａｎｄｉｏｎｅｘｃｈａｎｇｅｃｈｒｏｍａｔｏｇｒａｐｈｙ．Ｔｈｅｓｅｗｅｔｐｒｏｃｅｓｓｅｓ，ｈｏｗｅｖｅｒ，ｒｅｑｕｉｒｅｎｏｔｏｎｌｙｃｏｍｐｌｉｃａｔｅｄｔｒｅａｔｍｅｎｔｓｂｕｔａｌｓｏｍａｎｙｒｅｐｅａｔｅｄｏｐｅｒａｔｉｏｎｓ．Ｔｈｕｓ，ａｓｅａｒｃｈｆｏｒｎｏｖｅｌｐｒｏｃｅｓｓｅ…     

Synthesis and photoluminescence studies of Ba(Gd,Ln)B9O16:Eu3+(Ln=La,Y) phosphors for n-UV LED lighting and display devices

BaGdB9O16:Eu3+ and Ba(Gd,Ln)B9O16:Eu3+(Ln=La, Y) phosphors were synthesized by solid state diffusion method. The X-ray diffraction, scanning electron microscopy(SEM) and photoluminescence properties were investigated. The as-synthesized BaGdB9O16:Eu3+ and Ba(Gd,Ln)B9O16:Eu3+(Ln=La, Y) phosphors showed strong red emission under ultraviolet light excitation. By partially substituting Gd3+ by La3+ and Y3+ ions in the host BaGdB9O16:Eu3+ materials, the maximum emission intensity was observed for the optimum composition of BaGd0.91La0.8B9O16Eu0.01 phosphor. The experimental results indicated that the Eu doped BaGdB9O16 and Ba(Gd,Ln)B9O16(Ln=La, Y) phosphors were promising red phosphors, which might find potential applications in near-UV excited LED lighting as well as display devices. Comparison of as-synthesized phosphors with standard phosphor used in CFL(compact fluorescent lamp) was also done. Energy transfer mechanism of Gd3+ to Eu3+ was also discussed in this paper.     

Study on spectroscopic properties of GdOBr:RE3+ (RE=Eu, Tb, Ce)

Rare earth ions doped gadolinium oxybromide phosphors GdOBr:RE3 (RE=Eu, Tb, Ce) were synthesized by the method of solid-state reaction at high temperature, and the VUV-VIS spectroscopic properties of the phosphors were systematically investigated. Under the excitation of VUV or UV source, the phosphors doped with Eu3 and Tb3 show a bright and sharp emission at around 620 nm corresponding to the forced electric dipole 5D0→7F2 transition of Eu3 , and at around 544 nm corresponding to the 5D4→7F5 transition of Tb3 , respectively. For GdOBr:Ce3 , a broader and intense emission spanned 370-500 nm corresponding to the d-f transition of Ce3 was observed. The excitation spectra were also analyzed.     

Preparation and Electrical Transport Properties of Perovskite Oxide Ln0.5Sr0.5CoO3

The superfine powders of Ln0.5 Sr0.5 CoO3 （Ln = La, Pr, Nd, Sm, Eu） were obtained by solid state reactions. The crystal structure and electrical transport properties of samples doped with different rare earth elements as well as the forming process of the Perovskite structure were studied. The result shows that when the temperature reaches 1200 ℃, the samples will become a steady and unitary Perovskite phase by solid state reactions. The conductive behavor at low temperature is consistent with small polaron mechanism （i. e., localized electronic carriers having a thermally activated mobility）. However, the maximum of conductivity appears at about 700 ℃, and the conductivity of La0.5Sr0.5CoO3 is the biggest in the intermediate-temperature （600 - 850 ℃ ）, so it is fit for cathode material of intermediate-temperature solid oxide fuel cells.     

Synthesis, Characterization and Thermal Decomposition of Ln (Me2dtc)3(phen) (Ln=La, Pr, Nd, Sm)

Four solid complexes of Ln(Me2dtc)3(phen) (Ln=La, Pr, Nd, Sm) were synthesized in anhydrous ethanol by the reaction of lanthanide chloride low hydrate with the mixed ligand of sodium dimethyldithiocarbamate and 1, 10-phenanthroline·H2O (phen·H2O), and characterized by elemental analysis, IR spectroscopy, TG-DTG, and X-ray diffraction analysis. TG-DTG with X-ray powder diffraction showed that these compounds could decompose to lanthanide sulfides at relatively lower temperature, which indicated that the title complexes could be favorable precursors to prepare lanthanide sulfides.     

Preparation and luminescent properties of CaF2:Ln3+ (Ln:Er,Er/Yb)/Nafion composite films

In this work, CaF_2:Ln~(3+)(Ln:Er,Er/Yb)/Nafion composite films were prepared using Nafion as modifications and matrices by dripping method. The composite films were characterized by Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD) and scanning electron microscopy(SEM). Composite films are transparent and CaF_2:Ln~(3+)(Ln:Er,Er/Yb) nanoparticles are well dispersed in Nafion films.The thicknesses of CaF_2:Er~(3+)/Nafion and CaF_2:Er~(3+),Yb~(3+)/Nafion composite film are about 77 and 73 μm,respectively. The nanoparticles in composite film possess cubic phase. CaF_2:Er~(3+),Yb~(3+)/Nafion composite film has stronger characteristic emission of Er~(3+) around 1530 nm with full width at half-maximum(FWHM) of 73 nm and longer luminescence lifetimes of 22.04 μs(25.03%) and 100.77 μs(74.97%).     

Preparation of Stable CaS∶Eu~(2+), Tm~(3+) Phosphor

Alkalineearthsulfides (AES)havebeenfoundtobeexcellentandversatilephosphor ,andrareearthsasactivatorshavebeenintensivelyinvestigated[1～ 7] .Theyholdpromiseforapplicationsinphoto ,electro ,cathoderay ,fieldemissiondisplaysandluminescencepaints[8,9] .However ,alkalineearthsulfidesasaphos phorhosthavebeenfoundtobelimitedinapplica tion ,duemainlytoitssensitivetomoistureandotheratmosphericcomponents .Theirchemicalstabilityagainstatmosphericcarbondioxideandmoisturecouldbeenhancedthroughthegoodcryst…     

化学气相沉积技术与材料制备

概述化学气相沉积技术是一般原理与技术，总结化学气相沉积技术在材料制备方面的发展与应用状况，着重介绍化学气相沉积技术在制备贵金属薄膜和涂层领域的最新进展。     

Study on spectroscopic properties of GdOBr:RE (RE=Eu, Tb, Ce)

Rare earth ions doped gadolinium oxybromide phosphors GdOBr:RE³⁺ (RE=Eu, Tb, Ce) were synthesized by the method of solid-state reaction at high temperature, and the VUV-VIS spectroscopic properties of the phosphors were systematically investigated. Under the excitation of VUV or UV source, the phosphors doped with Eu³⁺ and Tb³⁺ show a bright and sharp emission at around 620 nm corresponding to the forced electric dipole ⁵D₀ → ⁷F₂ transition of Eu³⁺, and at around 544 nm corresponding to the ⁵D₄ → ⁷F₅ transition of Tb³⁺, respectively. For GdOBr:Ce³⁺, a broader and intense emission spanned 370–500 nm corresponding to the d-f transition of Ce³⁺ was observed. The excitation spectra were also analyzed.     

纳米YVO4:Ln(Ln=Eu,Tm,Dy)发光粉的研制及与相应块体发光粉的光谱对比

采用络合溶胶—凝胶法合成出3种YVO4∶Ln(Ln=Eu,Tm,Dy)纳米发光粉,并且对纳米YVO4∶Ln与自合成的块体YVO4∶Ln的红外光谱(FTIR),荧光光谱和X-射线衍射以及粒径的分布进行了对比研究。实验结果证明,当钒基稀土发光材料粒径达到纳米级以后,由于纳米粒子的一些特性,导致发光材料的光谱与块体材料相比有了较大的不同,出现了不同程度的蓝移现象。并且纳米发光材料的发光强度较块体发光材料的强度有一定程度的增强。     

Luminescence studies of MBrCl： Eu2＋ （M=Ca, Sr, Ba）

Europium doped MBrCl (M=Ca, Sr, and Ba) phosphors were prepared by solid state reaction in reductive atmosphere. Photolu-minescence (PL), photostimulated luminescence (PSL) after X-ray irradiation and optical absorption studies of MBrCl:Eu2+ (M=Ca, Sr, and Ba) revealed that: (1) blue light emission, under the excitation of 300 nm, was observed in all these phosphors; (2) the shape of the emission spectra in CaBrCl:Eu2+ could be changed by varying the bromine/chlorine ratio during synthesis, while that in SrBrCl:Eu2+ and BaBrCl:Eu2+ showed no change; and (3) PSL was observed in SrBrCl:Eu2+ and BaBrCI:Eu2+ after X-ray irradiation. Difference absorption spectrum (DAS) in SrBrCl:Eu2+ showed two broad bands centered at about 470 and 570 nm, and DAS in BaBrCI:Eu2+ showed two bands at about 550 and 675 nm, respectively. This enabled the use of He-Ne laser (633 nm) or even semiconductor light-emitting diodes (LED) instead of gas lasers for photostimulation.     

Co-Precipitation Preparation and Luminescent Behavior of (Y,Gd)BO3∶ Eu Phosphor

(Y,Gd)BO3∶ Eu phosphors were prepared by co-precipitation precursors, and luminescent properties were investigated. The precursors were synthesized by introducing hydroxyl ion to mixed solution of rare earth nitrates and boric acid, either through adding ammonia(precursor 1)or through controlled release of hydroxyl ion of urea(precursor 2). The precursors were fired in air at 1000 ℃ for 2 h. Resulted phosphor synthesized with precursor 1 has non-uniformed particle with mean diameter of about 3 μm, while that with precursor 2 exhibits uniformed near spherical-like morphology with mean diameter of about 300 nm. Phosphors with the two methods exhibit same crystal structure as that of commercial one. Emission spectra of the samples indicate that the sample prepared with precursor 2 shows relative higher intensity(exited by 172 nm VUV)than that prepared with the other precursor.