共查询到19条相似文献,搜索用时 115 毫秒
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Y_(2-x)Ho_x(WO_4)_3的制备及其热膨胀性能研究 总被引:1,自引:0,他引:1
采用固相化学反应法制取Y2-xHox(WO4)3(x=0.0~0.8,1.5~2.0)系列固溶体,利用高、低温X射线衍射方法研究Y2-xHox(WO4)3系列固溶体的热膨胀性能,并用热重法分析Y2-xHox(WO4)3所带的结晶水分子数目。由TOPAS软件计算出的晶胞参数随温度的变化可以看出,Y2-xHox(WO4)3{x=0.2,1.8}的化合物沿着3个晶向都是呈负热膨胀变化的,表明Y2-xHox(WO4)3这一系列固溶体均有负热膨胀性。 相似文献
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本文研究了[Co(NH_3)_4CO_3]Cl、[Co(en)_2CO_3]C1分别与NH_4SCN在100℃发生的固相取代反应.[Co(NH_3)_4CO_3]Cl与NH_4SCN反应生成trans-[Co(NH_3)_4(NCS)_2]~+;[Co(en)_2CO_3]Cl与NH_4SCN反应先生成cis-[Co(en)_2(NCS)_2]~+,然后转化成trans-(Co(en)_2(NCS)_2]~+。采用气相色谱、红外光谱、X粉末衍射和核磁共振法对相应反应体系及其产物进行了测试,推测反应按S_(N~2)机理进行。 相似文献
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在活性炭还原气氛下高温固相法合成了Ba3(PO4)2:Ce3+,Dy3+紫外发射荧光粉。XRD图谱表明,烧结温度为1100℃时保温处理3 h,样品为单相的Ba3(PO4)2型六方晶系结构。荧光光谱显示:单掺Ce3+样品中,Ce3+掺杂浓度为8%(摩尔分数)时样品的发光最强,发射峰的位置处在350 nm附近(Ce3+的2D→2F5/2和2D→2F7/2跃迁发射)。适量的Sr2+取代部分Ba2+离子,改变了基质晶格环境,使样品的发光强度得到提高且发射峰向长波方向红移。引入Dy3+作为敏化剂,样品发射峰红移到386 nm,亮度增强,主要是由于Dy3+和Ce3+之间发生了有效的能量传递过程。确定了Dy3+的最佳掺杂浓度为3%,发光强度提高了27%。 相似文献
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采用高温固相法合成了新型特效Na离子吸附剂Li1 xLaxZr2-x(PO4)3.对不同条件下合成的吸附剂进行了XRD结构分析以及SEM分析和IR分析,并对其吸附性能进行了测定.XRD结构分析表明,当x≤0.4时均能得到与LiZr2(PO4)3相同的晶体结构.SEM分析表明,合成的吸附剂分散性好,粒径范围在5~20μm之间.吸附性能测定结果表明,少量La的加入使Li1 xLaxZr2-x(PO4)3对Na离子产生了特效吸附作用,La离子掺杂是改善LiZr2(PO4)3吸附性能的一条有效途径,当x=0.4时,在pH值为10.0~11.0条件下,Li1 xLaxZr2-x(PO4)3的吸附容量达到48.3mg/g. 相似文献
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为了探究在Dy~(3+)掺杂Ba_3Y(PO_4)_3荧光粉中共掺Eu~(3+)离子对其发光性能的影响,我们采用传统高温固相法制备了一系列Dy~(3+)、Eu~(3+)单掺杂和共掺杂Ba_3Y(PO_4)_3荧光粉。通过X射线衍射(XRD)、荧光发射光谱和荧光衰减曲线对样品进行了表征。结果表明,所制备的荧光粉呈闪铋矿立方相。在近紫外光激发下,Ba_3Y(PO_4)_3∶Dy~(3+)发射光谱在487和578 nm处有两个窄带发射峰,呈冷白光发射;Ba_3Y(PO_4)_3∶Eu~(3+)发射光谱的窄带发射位于594和616 nm处,呈发橙红光。在Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)中,由于Eu~(3+)离子补偿Dy~(3+)冷白光发射所缺的红色组分,从而实现了色纯度高、色温适中的暖白光发射。进一步探索了Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)荧光粉发光机理。所制备的Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)单基质白光荧光粉在白光近紫外激发白光二极管(UVWLED)领域具有潜在应用价值。 相似文献
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制备方法对负热膨胀性ZrW2O8粉体的颗粒大小以及负热膨胀性能影响的研究 总被引:10,自引:0,他引:10
采用共沉淀法、分步固相法和溶胶凝胶法制备负热膨胀性ZrW2O8粉体。以XRD、SEM和TEM对产物结构及形貌进行表征,以原位X射线衍射分析粉体的负热膨胀特性。结果表明3种方法所制备的粉体均为单一立方结构的α-ZrW2O8相,共沉淀法制备的粉体颗粒较大,平均尺寸约为2.5 μm × 3.0 μm,溶胶凝胶法制备的颗粒最小,平均尺寸达到100 nm。所得粉体均表现为较强的负热膨胀特性,当粉体粒径相差不大时,负热膨胀系数变化很小,当颗粒粒径降低到纳米级时,负热膨胀系数有减小的趋势。 相似文献
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E. I. Voit A. V. Voit A. A. Mashkovskii N. M. Laptash V. Ya. Kavun 《Journal of Structural Chemistry》2006,47(4):642-650
Ammonium oxofluorotungstates, (NH4)2WO2F4 and (NH4)3WO3F3, are characterized by vibration spectroscopy and quantum chemistry methods with the use of NMR 19F and 1H data. It is shown in the approximation of the density-functional theory that in isolated octahedrons [WO2F4]2? and [WO3F3]3? the mutual arrangement of oxygen atoms in cis-position corresponds to the energy minimum. The presence of intraspheric disorder in [WO3F3]3? (unlike [WO2F4]2?) explains the complex character of vibrational spectra of this anion and eliminates existent in the literature differences in their interpretation (between C 2v and C 3v structure variants). Models of intraspheric dynamics of [WO3F3]3? are discussed. 相似文献
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Pol SV Pol VG Kessler VG Seisenbaeva GA Solovyov LA Gedanken A 《Inorganic chemistry》2005,44(26):9938-9945
This article reports on the fabrication of WO(3) nanorods using an efficient straightforward synthetic technique, without a catalyst, and using a single precursor. The thermal dissociation of WO(OMe)(4) at 700 degrees C in a closed Swagelok cell under an air/inert atmosphere yielded W(18)O(49) nanorods. Annealing of W(18)O(49) at 500 degrees C under an air atmosphere led to the formation of pure WO(3) nanorods. The obtained products are characterized by morphological (scanning electron microscopy and transmission electron microscopy), structural (X-ray diffraction analysis, high-resolution scanning electron microscopy, and Raman spectroscopy), and compositional [energy-dispersive X-ray and elemental (C, H, N, S) analysis] measurements. The mechanism of the formation of nonstoichiometric W(18)O(49) nanorods is supported by the measured analytical data and several control experiments. 相似文献
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The hydroxy yttrium hexaborate,Y[B2O3(OH)]3,has been synthesized under mild hydrothermal conditions at 458 K.The crystal structure was solved and refined from single-crystal X-ray diffraction.It adopts a trigonal space group R3c(No.161) with a = 8.3942(4),c = 20.6484(12) ,V = 1260.03(12) 3,YB6H3O12,Mr = 348.79,Z = 6,Dc = 2.758 g/cm3,F(000) = 1008,μ = 7.015 mm-1,R = 0.0321 and wR = 0.0772.Its crystal structure is made up of six-membered rings,alternating three-connected [BO3(OH)] tetrahedra and planar [BO3] trigonal groups,which are interconnected with each other by sharing their common oxygen corners to form a three-dimensional framework structure with six-membered ring channels that are occupied by the yttrium atoms and run along the c axis.FT-IR,Raman,and TG-DTA results are also presented. 相似文献
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A New Structure Type for the Rare Earth Oxotungstate FeCe(WO4)W2O8 = FeCe(WO4)3 Single crystals of the hitherto unknown compound FeCe(WO4)3 have been prepared by crystallization from melts of Fe2O3, CeO2 and WO3. It crystallizes with triclinic symmetry, space group P1 , a = 7,486(3); b = 7,528(1); c = 16,502(4) Å, α = 101,00(2); β = 96,62(3); γ = 98,62°; Z = 2. Tungsten shows octahedral and tetrahedral coordination by oxygen. The crystal structure is characterized by layers related to the Scheelite and Wolframite type. Thermogravimetric measurements led to a lost of oxygen during reaction. It results in a decrease of the oxidation states of Fe3+ and Ce4+ respectively, as will be discussed using magnetic measurements and calculations of the Coulomb terms of lattice energy. The structure contains a one-fold coordinated oxygen. 相似文献
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A. Ya. Neiman A. V. Karapetyan N. N. Pestereva 《Russian Journal of Electrochemistry》2014,50(1):58-69
Composites {Me2(WO4)3 ? xWO3} (Me = Sc, In) (x = 0.5–99%) are synthesized and characterized by XRD and electron microscopy methods and also by the density and specific surface measurements. Temperature dependences of the total conductivity of composites are measured. The contributions of σtot and σel are assessed by the $\sigma (a_{O_2 } )$ and EMF methods. The concentration dependences of conductivity and activation energy are plotted based on the σtot and σion data. It is shown that (a) in the interval x = 0–30 vol % WO3 (0–70 mol %), the conductivity is independent of composition and the ionic component prevails; (b) in the interval x = 60–94.5 vol % (90–99 mol %), the electron conductivity prevails and increases with the increase in x; (c) in the x interval of 30–60 vol % WO3 (70–90 mol %), the conductivity is mixed, i.e., electron(n-type)-ionic; the latter region represents the transition interval from ionic to electron conductivity as x increases. These data are compared with the results obtained earlier for MeWO4-WO3 composites (Me = Ca, Sr, Ba). As regards the structural topology, the {Me2(WO4)3 ? xWO3} composites pertain to the randomly distributed type. It is shown that in contrast to {MeIIWO4 · xWO3} composites, the composites under study do not form the nonautonomous interface phase with the high ionic conductivity. The possible reasons for the observed differences in the topology and the conduction type of composites based on MeWO4 and Me2(WO4)3 are analyzed. 相似文献
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The parameters of ligand field of laser crystal Na~(3+):KY(WO_4)_2 and Nd~(3+):KGd(WO_4)_2are obtained by a scheme which involved intermediate coupling and ligand field interaction.Thecalculated Stark-levels are in good agreement with the experimental values. 相似文献