用3种方法合成Y_3Al_5O_(12)∶RE~(3 )(RE=Eu,Dy)发光粉的对比研究

以金属硝酸盐为反应原料 ,分别采用柠檬酸 凝胶法、共沉淀法和固相法制备了YAG和YAG∶RE3 (RE =Eu ,Dy) (1% ,摩尔分数 )发光粉 ,并通过XRD ,TG DTA和发光光谱对样品进行了表征。柠檬酸 凝胶法、共沉淀法和固相法制备的YAG和YAG∶Eu的晶相形成温度分别是 80 0和 90 0℃。Eu3 在非晶态和晶态YAG中其激发和发射光谱有明显差异 ,在一定温度范围内 ,发光强度随烧结温度的升高而增强。由于碳杂质的存在 ,90 0和 10 0 0℃下柠檬酸 凝胶法制备样品的发射强度较其他两种方法低。     

三种方法制备CaGdAlO_4∶Eu~(3+)荧光粉及其发光性质研究

分别采用柠檬酸溶胶-凝胶法、半干半湿法和高温固相法制备了CaGdAlO4∶Eu3+荧光粉,并用X射线衍射(XRD)分析、场发射扫描电镜(FE-SEM)观察和荧光光谱分析研究了不同制备方法和制备条件对CaGdAlO4∶Eu3+形貌、粒径和发光性质的影响。XRD结果表明,柠檬酸溶胶-凝胶法、半干半湿法和固相法制备CaGdAlO4∶Eu3+生成纯相的温度分别为900,1200和1400℃。FE-SEM照片显示CaGdAlO4∶Eu3+颗粒粒径随温度的升高而增大,在同一烧结温度下,粒径大小为柠檬酸溶胶-凝胶法最小,半干半湿法居中,高温固相法最大而且团聚现象严重。以280 nm近紫外光激发,CaGdAlO4∶Eu3+发出明亮的橙红色荧光,以Eu3+的5D0→7F2跃迁为主,发光强度随烧结温度的升高而增加,在1400℃烧结温度下,以半干半湿法得到的样品发光最强。室温和低温发射谱中Eu3+的5D0→7Fj发射峰的数目都表明:Eu3+在CaGdAlO4中只占据偏离反演中心的一种格位。     

三种方法制备CaGdAlO4:Eu3+荧光粉及其发光性质研究

分别采用柠檬酸溶胶-凝胶法、半干半湿法和高温固相法制备了CaGdAlO4：Eu^3＋荧光粉，并用X线衍射（XRD）分析、场发射扫描电镜（FE—SEM）观察和荧光光谱分析研究了不同制备方法和制备条件对CaGdAlO4：Eu^3＋形貌、粒径和发光性质的影响。XRD结果表明，柠檬酸溶胶-胶法、半干半湿法和固相法制备CaGdAlO4：Eu^3＋生成纯相的温度分别为900，1200和1400℃。FE—SEM照片显示CCaGdAlO4：Eu^3＋颗粒粒径随温度的升高而增大，在同一烧结温度下，粒径大小为柠檬酸溶胶-凝胶法最小，半干半湿法居中，高温固相法最大而且团聚现象严重。以280nm近紫外光激发，CaGdAlO4：Eu^3＋发出明亮的橙红色荧光，以Eu^3＋的^5D0→^7F2跃迁为主，发光强度随烧结温度的升高而增加，在1400℃烧结温度下，以半干半湿法得到的样品发光最强。室温和低温发射谱中Eu^3＋的^5D0→^7Fj，发射峰的数目都表明：Eu^3＋在CaGdAlO4中只占据偏离反演中心的一种格位。     

不同方法制备CaMoO4∶0.05Eu3+红色荧光粉的对比研究

分别以高温固相法、溶胶-凝胶法、水热法和共沉淀法合成Eu3+掺杂的CaMoO4红色荧光粉,通过X-射线衍射(XRD)、场发射扫描电镜(FESEM)、傅立叶变换红外光谱(FTIR)、光致荧光光谱(PL)进行表征,考察荧光粉晶相、形貌及发光性能对制备方法的依赖性。实验表明,由于Ca2+的半径(0.099 nm)与Eu3+半径(0.094 7 nm)大小相差不大,Eu3+容易取代Ca2+的位置进入晶格,Eu3+掺杂的CaMoO4在晶体结构上保持白钨矿结构。FESEM结果表明:未经后处理的水热法所得样品为片状、多孔结构;高温固相法所得样品尺寸大、团聚严重;溶胶-凝胶法所得样品分散度好、呈条形结构;共沉淀法所得样品形貌、尺寸比较均一。荧光光谱显示,四种样品发光强度差异很大,共沉淀法制得样品的发光强度为未经后处理的水热法制得样品的6-7倍,该现象主要是由样品形貌及表面缺陷的差异引起的。     

Er3+,Sm3+掺杂纳米晶体NaNbO3的合成和上转换发光研究

首先用水热法合成了NaNbO3样品,然后用固相法分别合成了NaNbO3,NaNbO3:Er3+,NaNbO3:Sm3+样品,X射线衍射结果表明所制备的粉体NaNbO3(水热法200℃和固相法900℃退火),NaNbO3:Er3+(900℃退火),NaNbO3:Sm3+(900℃退火)为立方相结构,在退火温度800,950和1000℃时是正交晶系,长方体结构.该粉末在980 nm LD激发下,分别发射出中心波长约为526 nm绿色,547nm绿色和662 nm红色(掺Er3+)、526 nm绿色,550 nm绿色和660 nm红色(掺Sm3+)的上转换荧光.探讨了Er3+,Sm3+的上转换发光机制.研究了晶体的对称性和退火温度对NaNbO3:Er3+样品上转换发光强度的影响,结果表明,随着晶体的对称性降低和退火温度的提高,NaNbO3:Er3+样品的上转换发光强度增强.     

GdAlO_3:Er~(3+),Yb~(3+)荧光粉的制备与上转换发光性能

采用共沉淀、溶胶-凝胶和固相反应法制备了GdAlO3:Er3+,Yb3+荧光粉.借助X射线衍射、扫描电子显微镜、傅里叶变换红外光谱、N2-吸附、吸收光谱和荧光光谱等手段研究了不同方法制备的GdAlO3:Er3+,Yb3+荧光粉结构、形貌、表面基团和光吸收及上转换发光性能.结果表明:用共沉淀法比固相反应法和溶胶-凝胶法可以在更温和的条件下制得纯相GdAlO3:Er3+,Yb3+荧光粉,用共沉淀法和溶胶-凝胶法制备的GdAlO3:Er3+,Yb3+荧光粉颗粒都在纳米尺寸,溶胶-凝胶法制得的样品存在相对严重的颗粒团聚现象,而用固相反应法制备的荧光粉为微米级颗粒.GdAlO3:Er3+,Yb3+荧光粉在980 nm激发的上转换发射光谱包含波长为524和546 nm的绿光与659 nm的红光,且三种方法制备的样品绿光发射强度都显著高于红光.不同方法制备的荧光粉上转换发光强度和红光/绿光强度比相差较大,共沉淀法制备的样品上转换发光强度要显著高于固相法以及溶胶-凝胶法制备的样品,而溶胶-凝胶法制备的样品发光中红光/绿光相对强度比最高.红外光谱显示,不同方法制备的GdAlO3:Er3+,Yb3+荧光粉表面OH-、CO32-及CO2官能团含量不同,溶胶-凝胶法制备的样品要明显高些.基于红外光谱、不同Er3+和Yb3+离子掺杂浓度及不同激光功率上转换发光的结果,对Er3+和Yb3+之间的能量传递过程及不同方法制备荧光粉的上转换发光性能进行了讨论.     

微波合成对SrAl2O4:Eu2+, Dy3+晶相和铕的价态的影响

为了在较低温度下合成性能优良的SrAl2O4：Eu^2＋,Dy^3＋（SAO—ED）发光材料,采用溶胶-凝胶-微波法在900℃烧结30min合成SAO—ED发光材料。产品的发光性能优于传统高温固相法1400℃烧结3h制备的产品。根据Henderson和Taylor提出的公式对SrAl2O4的XRD数据进行了量化,计算出单斜晶系（M）和六方晶系的比例;结果表明,溶胶-凝胶-微波法制备的产品中只有单斜晶系存在,而高温固相法制备的产品中有六方晶系存在,六方晶系不发光。另外,产品采用XANES表征了Eu离子存在的价态,发现溶胶一凝胶微波法制备的产品中残留的Eu^3＋的比例远低于传统高温固相法制备的产品。以上两种原因导致了产品的发光性能优于高温固相法制备的产品。     

共沉淀-熔盐焙烧法制备Y2O3:Eu及其发光性能的研究

采用共沉淀-熔盐焙烧法制备了Y2O3：Eu红色荧光粉,研究分析了EDTA、柠檬酸＋氨水、淀粉等3类络合剂、沉淀温度及熔盐对其发光性能、粒度及形貌等的影响.研究结果表明： 采用柠檬酸＋氨水为络合剂、草酸为沉淀剂制备钇铕的草酸盐前驱体,然后加入（Na2CO3＋S＋NaCl）复合熔盐在1200 ℃下焙烧2 h即可制得发光强度高出商用粉5%的近球形Y2O3：Eu.     

SrAl_2O_4∶Eu~(2 ),Dy~(3 )纳米长余辉发光材料的制备与表征

采用溶胶鄄凝胶法制备了SrAl2O4∶Eu2 ,Dy3 纳米长余辉发光材料,研究了pH值、反应温度和络合剂等对溶胶鄄凝胶形成的影响,研究了灼烧温度对SrAl2O4∶Eu2 ,Dy3 晶相、颗粒尺度和发光性能的影响。利用XRD,SEM,光谱分析等手段对产物进行了结构和性能分析。实验结果表明,在800℃时SrAl2O4晶相开始形成但没有发光,而在1100℃烧结的样品则具有很好的发光性能。样品平均晶粒尺寸随灼烧温度升高而增加,平均晶粒尺寸为20~40nm。样品的激发光谱是峰值在240,330,378和425nm的连续宽带谱,发光光谱是峰值在523nm的宽带谱,与SrAl2O4∶Eu2 ,Dy3 粗晶材料相比,发光光谱发生了“红移”现象。样品的热释光峰值位于157℃,与SrAl2O4∶Eu2 ,Dy3 粗晶材料相比,峰值向低温移动了13℃。     

ZnO/Eu~(3+)发光材料的高温固相合成及其发光性能

采用高温固相法制备了ZnO/Eu3+红色长余辉发光材料.应用正交试验设计法(每个因素取3个水平,选用L9(34)正交试验表),以初始亮度为指标,研究了煅烧温度、Eu3+质量分数、敏化剂Li+质量分数、煅烧时间等4个因素对发光性能的影响;利用X射线衍射仪对合成的ZnO/Eu3+发光材料进行了物相分析,应用荧光分光光度计测定了样品的激发光谱和发射光谱,应用照射计测定了样品的发光特性.结果表明,当各个因素在水平范围内变化时,所制备的样品均具有ZnO晶格结构;荧光粉的主激发峰位于365 nm和458 nm处,主发射峰位于480 nm、570 nm和600 nm~640 nm,对应于Eu3+的4f和5d间的激发和发射.所确定的最佳合成条件为:煅烧温度850℃,w(Eu3+)=4%,w(Li+)=2.5%,煅烧时间3 h.     

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.     

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.     

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.     

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。     

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.     

SnSbBiS4-SnS and SnSbBiS4-Sn2Sb6S11 sections of the SnS-Sb2S3-Bi2S3 ternary system

SnSbBiS₄-SnS and SnSbBiS₄-Sn₂Sb₆S₁₁ sections were studied by physicochemical methods (DTA, X-ray powder diffraction, microstructure observation, and microhardness measurements). These sections were found to be eutectic quasi-binary sections of the SnS-Sb₂S₃-Bi₂S₃ ternary system. Solid solution regions based on the initial components were found on either side of the sections. Alloys in the solid solution region are p-type semiconductors.     

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.