NaGdF_4:Eu~(3 )的结构和VUV荧光性质

利用水热方法合成了纯度较高的六方结构的 NaGdF4,在氧气存在条件下 950℃加热处理可以使其转变为 CaF2型立方结构。在真空紫外光激发下,六方结构的 NaGdF4∶ Eu3＋中的 Gd3＋离子吸收一个光子,并将能量分两步传递给 Eu3＋离子,发生双光子发射。立方结构的 NaGdF4∶ Eu3＋中存在有一定量的氧离子取代缺陷,使 Gd3＋离子 4f-5d跃迁移到 177nm附近,这与惰性气体放电产生的真空紫外光波长一致。     

GdVO4：Eu^3＋的真空紫外激发光谱研究

报道GdVO4:Eu^3 的光致发光光谱和真空紫外－紫外激发光谱。GdVO4:Eu^3 是高效率的真空紫外－紫外激发荧光材料。GdVO4:Eu^3 在60－350nm真空紫外－紫外波段的激发可能主要来源于基质的吸收,有明显的Eu^3 及Gd^3 的4f^n-15d吸收,在GdVO4:Eu^3 中,存在如下能量传递过程：VO4^3-→Eu^3 ,Gd^3 →Eu^3 ,Gd^3 →VO4^3-→Eu^3 ;通过后两个过程,Gd^3 -Eu^3 可实现量子剪裁。     

RbLn2F7的水热合成及RbLn2F7:Eu3+(Ln=Gd,Y)的VUV光谱

利用水热方法合成出RbLn2F7（Ln=Gd，Y，Er，Yb和Lu），均为六方RbEr2F7型结构。掺杂Eu^3＋离子样品的光谱表明水热产物中氧杂质含量极低。在RbGd2F7：Eu^3＋（0．5mol％）的激发光谱中只观测到Gd^3＋离子f-f跃迁，Eu^3＋离子的激发跃迁很弱。激发Gd^3＋离子到^6IJ能级后，观测到Eu^3＋离子的特征发射，Gd^3＋离子与Eu^3＋离子之间存在能量传递过程。Eu^3＋离子的^5D0→^7F1和^5D0→F2跃迁发射较强，表明稀土离子在六方HbLn2F7中处于非中心对称的格位。     

稀土离子(Gd3+,Eu3+)加载于纳米介孔ZrO2中的发光

水热合成法制备的高度有序多孔ZrO2具有规则六角排列，均匀纳米孔洞（约1．8nm)，丰富的表面，界面态及比表面积和强的蓝－（近）紫外光发射，使其较常规体材料有更优异的性质，以稀土离子为探针，研究了Gd^3 ,Eu^3 在这些纳米微孔中的发光行为，结果表明，500摄氏度下，介孔ZrO2与稀土离子相作用并有效地将能量传递给稀土离子，增进稀土离子发光，而在ZrO2:Gd-Eu体系中，Gd^3 在ZrO2与Eu3 间起桥梁作用，使基质ZrO2→Eu^3 的能量传递更为有效。     

GdF3∶Eu3+/NaGdF4∶Eu3+纳米晶的水热合成及发光性质

采用水热法,以聚乙二醇(400)为分散剂,以NaOH和HNO3溶液调节初始溶液pH值,合成GdF3∶Eu3+和NaGdF4∶Eu3+纳米晶。XRD和SEM结果表明:在酸性溶液(pH=3,5)、中性溶液(pH=7)和碱性溶液(pH=9)中,分别获得具有正交结构的GdF3∶Eu3+纳米晶,GdF3∶Eu3+和NaGdF4∶Eu3+混合晶,六方结构NaGdF4∶Eu3+棒状微米晶。根据Scherrer公式估算pH=3和pH=5时制备纳米晶的一次性粒径分别为49和28 nm。样品的发射光谱结果表明:特征发射峰来自于5D2、5D1、5D0到7FJ跃迁。在主晶相为GdF3样品中,主发射峰来自于Eu3+的5D0→7F1的磁偶极跃迁;晶相为NaGdF4样品的主发射峰来自于Eu3+的5D0→7F2电偶极跃迁。5D0→7F1和5D0→7F2跃迁发射相对强度比值显示:Eu3+在NaGdF4晶体中的格位对称性下降。激发光谱显示出Gd3+和Eu3+具有较好的能量传递。     

Eu3+掺杂YPO4的合成、结构及发光特性研究

以Eu^3＋掺杂YPO4为研究对象,通过简单水热法在200℃下制备了不同Eu^3＋掺杂浓度的YPO4纳米颗粒。采用X射线粉末衍射、透射电镜和荧光光谱对样品进行了表征,研究了Eu^3＋掺杂浓度对相结构、发光性能的影响。实验结果表明,通过调节掺杂Eu^3＋离子的浓度可以对样品的相结构进行调控。随着Eu^3＋掺杂浓度的提高,样品发生了从四方相到六方相,最后到单斜相的转变。因此通过不同Eu^3＋离子浓度的掺杂可以实现相结构的调控。荧光光谱测量发现所有发射均为Eu^3＋的f-f能级之间的特征跃迁,并且确定掺杂浓度为10％的样品具有最强的发光强度。     

Eu:GGG纳米荧光粉体制备及其光学特性

采用液相共沉淀方法并在不同烧结温度下制得了Eu：GGG荧光粉体。用X射线衍射分析了样品的结构，计算了其晶格常数，为1．2371nm。室温下，测量了Eu：GGG的光致发射光谱、激发光谱和荧光衰减曲线。激发光谱在波长240～287nm的谱带内和393。。处有强的激发，分别来自于Eu^3＋O2^-间的电荷迁移态吸收和Eu“的^7F0→^5L6的跃迁吸收，同时在274nm处也出现了Gd^3＋的^8S7/2→^6I1的特征吸收。393nm激发下，591nm处的发射峰最强，对应Eu^3＋的^5D0→^7F1的磁偶极跃迁，可能由于部分Eu^3＋处于反演中心对称格位所致。随着烧结温度升高，Eu：GGG的发光强度增强，这可能由于随着烧结温度升高，样品晶粒尺寸变大，单位体积内被激发的Eu^3＋离子数增加引起，而591nm发光的荧光寿命变短，可能是由Eu^3＋离子的能量共振传递过程中发光被陷阱捕获所致。     

尖吻蝮蛇毒抗凝血因子I的稀土离子荧光探针研究

稀土离子（Nd^3 ,Sm^3 ,Eu^3 ,Gd^3 ,Tb^3 )对抗凝血因子（ACFI）的内源荧光有不同程度的淬灭作用。稀土离子与ACI I 光滴定的结果表明，ACFI分子中有两个稀土离子结合位点，稀土离子和钙离子在ACF I分子中两个结合位点是共同的竞争结合位点。每个稀土离子与ACF I的结合常数K1和K2相接近，说明两个结合位点的结构可能基本一致。不同的稀土离子与ACF I之间有相近的结合常数K1或K2，表明ACF I分子中的两个结合位点在结构上都有较的柔性，这种结构柔性为钙离子在ACF I与活化凝血因子X的结合反应中所起的激活作用提供了结构基础。     

M2B5O9X：Eu，Tb（M=Ca,Sr;X=Cl,Br）荧光体的光谱特征

利用Eu^3 和Tb^3 稀土离子之间存在电子组态共轭性的特征,将其双掺于同一基质中,由于电子转移而产生Eu^2 ,使Eu^3 ,Tb^3 和Eu^2 共存于同一体系中,在空气中合成了M2B5O9X：Eu,Tb荧光粉,研究了其发光特征及影响作用。结果表明,Eu^3 ,Tb^3 和Eu^2 共存于同一基质中,且稀土离子的掺杂量对其光谱产生影响。     

乳清酸/异乳清酸体系荧光法测定铕、铽、镝

对比研究了乳清酸和异乳清酸对某些稀土离子特征荧光的增敏情况，发现异乳清酸比乳清酸更有效地使Eu^3 、Tb^3 、Dy^3 的特征荧光增敏。建立了乳清酸，异乳清酸体系荧光法测定Eu^3 、Tb^3 、Dy^3 的新方法，在乳清酸体系中Eu^3 、Tb^3 、Dy^3 的检出限分别是0．73、0．065mg，L，在异乳清酸体系中Eu^3 、Tb^3 、Dy^3 的检出限分别是0．88、0．0023、0．59mg/L。该方法用于混合稀土氧化物中Eu^3 、Tb^3 、Dy^3 含量的测定，结果满意。     

Phase relations in the K2W2O7-K2WO4-KPO3-Bi2O3 system and structure of K6.5Bi2.5W4P6O34

The phase relations in the cross-section of the K₂W₂O₇-K₂WO₄-KPO₃ containing 15 mol% Bi₂O₃ were undertaken using flux method. Crystallization fields of K_6.5Bi_2.5W₄P₆O₃₄, K₂Bi(PO₄)(WO₄), Bi₂WO₆, KBi(WO₄)₂ and their cocrystallization areas were identified. Novel phase K_6.5Bi_2.5W₄P₆O₃₄ was characterized by single-crystal X-ray diffraction: sp. gr. P−1, a=9.4170(5), b=9.7166(4), c=17.6050(7) Å, α=90.052(5)°, β=103.880(5)° and γ=90.125(5)°. It has a layered structure, which contains {K₇Bi₅W₈P₁₂O₆₈}_∞ layers stacked parallel to ab plane and sheets composed by potassium atoms separating these layers. Sandwich-like {K₇Bi₅W₈P₁₂O₆₈}_∞ layers are assembled from [W₂P₂O₁₃]_∞ and [BiPO₄]_∞ building units, and are penetrated by tunnels with K/Bi atoms inside. FTIR-spectra of K₂Bi(PO₄)(WO₄) and K_6.5Bi_2.5W₄P₆O₃₄ were discussed on the basis of factor group theory.     

Sol-gel synthesis of K3InF6 and structural characterization of K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18

K₃InF₆ is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K₂InC₁₀O₁₀H₆F₉, K₃InC₁₂O₁₄H₄F₁₈ and K₃InC₁₂O₁₂F₁₈. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K₃InF₆ by decomposition at high temperature. The crystal structure of K₃InC₁₂O₁₄H₄F₁₈ is characterized by complex anions [In(CF₃COO)₄(OH_x)₂]^(5−2x)− and isolated [CF₃COOH_2−x]^(x−1)− molecules with x=2 or 1, surrounded by K⁺ cations. The crystal structure of K₃InC₁₂O₁₂F₁₈ is only constituted by complex anions [In(CF₃COO)₆]³⁻ and K⁺ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K₂InC₁₀O₁₀H₆F₉ and K₃InC₁₂O₁₂F₁₈ were also performed at room temperature on pulverized crystals.     

KCl-KBO2-K2CO3, K2MoO4-KBO2-K2CO3, and K2WO4-KBO2-K2CO3 ternary systems

phase diagrams of KCl-KBO₂-K₂CO₃, K₂MoO₄-KBO₂-K₂CO₃, and K₂WO₄-KBO₂-K₂CO₃ ternary systems were studied by a calculation-experimental method and differential thermal analysis (DTA). The coordinates of ternary eutectics were determined to be E ₁: 622°C, 8.5 mol % KBO₂, 56.5 mol % KCl, and 35 mol % K₂CO₃; E ₂: 710°C, 23 mol % KBO₂, 43 mol % K₂CO₃, and 34 mol % K₂MoO₄; E ₃: 710°C, 23 mol % KBO₂, 43 mol % K₂CO₃, and 34 mol % K₂WO₄. The specific heats of melting of the eutectics were determined.     

Li2SO4-Na2SO4-H2O和Li2SO4- K2SO4-H2O溶液的体积性质

本文用高精度数字式振荡管密度计测定了288K至318K温度范围内Li₂SO₄ + Na₂SO₄ + H₂O和 Li₂SO₄ + K₂SO₄ + H₂O三元体系的密度。混合溶液的离子强度范围从0.1到4.5 mol.kg_–1,混合溶液中Na₂SO₄和K₂SO₄的离子强度分数为0.2,0.4,0.6和0.8。用密度实验值拟合得到了不同温度下Pitzer离子相互作用模型混合参数θ_V和 ψ_V,模型的计算值与实验值的偏差在±0.002 g.cm_–3以内。用Pitzer模型计算了不同离子强度下三元体系的混合体积。     

Solubility in the Na2Cr2O7-(NH4)2Cr2O7-K2Cr2O7-H2O system

Solubility in the Na₂Cr₂O₇-(NH₄)₂Cr₂O₇-K₂Cr₂O₇-H₂O four-component water-salt system at 25, 50, and 75°C was studied for the first time. Phase field boundaries for individual salts and potassium and ammonium dichromate solid solutions, monovariant lines, and invariant points were determined. Experimental data were used to optimize the looped isohydric process of potassium dichromate preparation involving additional salts.     

NaBO2-NaCl-Na2CO3, NaBO2- Na2CO3-NaMoO4, NaBO2- Na2CO3-NaWO4, and NaBO2-NaCl-Na2WO4 ternary systems

The phase diagrams of the NaBO₂-NaCl-Na₂CO₃, NaBO₂-Na₂CO₃-Na₂MoO₄, NaBO₂- Na₂CO₃-Na₂WO₄, and NaBO₂-NaCl-Na₂WO₄ ternary systems were studied by a calculation-experimental method and differential thermal analysis. The coordinates of ternary eutectics were determined: E ₁: 612°C, 16 mol % NaBO₂, 42 mol % NaCl, and 42 mol % Na₂CO₃; E ₂: 568°C, 12 mol % NaBO₂, 28 mol % Na₂CO₃, and 60 mol % Na₂MoO₄; E ₃: 575°C, 12 mol % NaBO₂, 32 mol % Na₂CO₃, and 56 mol % Na₂WO₄; E ₄: 628°C, 8 mol % NaBO₂, 20 mol % NaCl, and 72 mol % Na₂WO₄; and E ₅: 655°C, 9 mol % NaBO₂, 53 mol % NaCl, and 38 mol % Na₂WO₄.     

Extension of the La7Mo7O30 structural type with La7Nb3W4O30 and La7Ta3W4O30 compounds

Two compounds of formula La₇A₃W₄O₃₀ (with A=Nb and Ta) were prepared by solid-state reaction at 1450 and 1490 °C. They crystallize in the rhombohedric space group R-3 (No. 148), with the hexagonal parameters: , and , . The structure of the materials was analyzed from X-ray, neutron and electronic diffraction. These oxides are isostructural of the reduced molybdenum compound La₇Mo₇O₃₀, which are formed of perovskite rod along [111]. An order between (Nb, Ta) and W is observed.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

Structural chemistry of Sr3Cr2WO9, Ca3Cr2WO9, and Ba3Cr2WO9

We have studied the preparation and crystallographic structure of three perovskite-type compounds: Sr₃Cr₂WO₉, cubic, the lattice parameter of which is a = 7.812Å; Ca₃Cr₂WO₉, tetragonal, the lattice parameters of which are a = 5.408 Å and c = 7.635Å; and Ba₃Cr₂WO₉, hexagonal, the lattice parameters of which are a = 5.691 Å and c = 13.957Å. We have compared these three structures and shown the relationship between the dimensions of the alkaline-earth metal and the existence of the different structures.     

Theoretical study of polyoxide clusters B20O30, Al20O30, V20O50, Si20O30H20, and Si20O30F20

The structural, electronic, and vibrational characteristics and energies of the isolated polyoxide clusters B₂₀O₃₀, Al₂₀O₃₀, V₂₀O₅₀, Si₂₀O₃₀H₂₀, and Si₂₀O₃₀F₂₀ and their complexes with the H⁻ ion and ammonia complexes Al₂₀O₃₀ · nNH₃ have been calculated by the density functional theory B3LYP method with different basis sets. The computation results show that the symmetric closo structure I _h with oxygen bridges located above the centers of the faces of an empty [M₂₀] dodecahedron is more favorable for V₂₀O₅₀, Si₂₀O₃₀H₂₀, and Si₂₀O₃₀F₂₀. For B₂₀O₃₀, the cage closo isomer is also more favorable than the other isomers, but its structure is severely distorted as compared to a dodecahedron and has a symmetry close to C ₃ . For Al₂₀O₃₀, the I _h structure corresponds to a high-lying local minimum of the potential energy surface. For Al₂₀O₃₀, a set of unusual puckshaped isomers of symmetry C _i , with different numbers of four-coordinate atoms ^IVAl and three-coordinate atoms ^IIIO, was localized; these structures are more than 90 kcal/mol more favorable than the dodecahedron I _h . The most favorable isomer of Al₂₀O₃₀ contains twelve four-coordinate atoms ^IVAl and four five-coordinate atoms ^VAl. The energies of dissociation of the most favorable M₂₀O₃₀ clusters into the M₂O₃ (C _2v ) and M₄O₆ (T _d ) fragments and, in the case of Al₂₀O₃₀, also into the Al₈O₁₂ (O _h ) and Al₁₂O₁₈ (D _3d ) fragments, have been estimated. The conclusion has been drawn that these clusters can, in principle, exist and can be experimentally detected in the isolated state. Analogous calculations have been performed for ammonia complexes Al₂₀O₃₀ · nNH₃ with n varying from 1 to 20. The effect of solvation on the relative stability of the dodecahedral and puckshaped isomers of the Al₂₀O₃₀ cluster is observed. The isomers with ammonia molecules in their first coordination sphere become much closer to one another on the energy scale; however, the dodecahedron remains a considerably less favorable intermediate. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 4, pp. 624–635.