A new promising phosphor, Na3La2(BO3)3:Ln (Ln=Eu, Tb)

We present an efficient way to search a host for ultraviolet (UV) phosphor from UV nonlinear optical (NLO) materials. With the guidance, Na₃La₂(BO₃)₃ (NLBO), as a promising NLO material with a broad transparency range and high damage threshold, was adopted as a host material for the first time. The lanthanide ions (Tb³⁺ and Eu³⁺)-doped NLBO phosphors have been synthesized by solid-state reaction. Luminescent properties of the Ln-doped (Ln=Tb³⁺, Eu³⁺) sodium lanthanum borate were investigated under UV ray excitation. The emission spectrum was employed to probe the local environments of Eu³⁺ ions in NLBO crystal. For red phosphor, NLBO:Eu, the measured dominating emission peak was at 613 nm, which is attributed to ⁵D₀-⁷F₂ transition of Eu³⁺. The luminescence indicates that the local symmetry of Eu³⁺ in NLBO crystal lattice has no inversion center. Optimum Eu³⁺ concentration of NLBO:Eu³⁺ under UV excitation with 395 nm wavelength is about 30 mol%. The green phosphor, NLBO:Tb, showed bright green emission at 543 with 252 nm excited light. The measured concentration quenching curve demonstrated that the maximum concentration of Tb³⁺ in NLBO was about 20%. The luminescence mechanism of Ln-doped NLBO (Tb³⁺ and Eu³⁺) was analyzed. The relative high quenching concentration was also discussed.     

Determination of the enthalpy of fusion of K3TaF8 and K3TaOF6

The areas of the fusion and crystallization peaks of K₃TaF₈ and K₃TaOF₆ have been measured using the DSC mode of the high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities and the temperature dependence of the used calorimetric method sensitivity, the values of the enthalpy of fusion of K₃TaF₈ at temperature of fusion 1039 K: Δ_fusH_m(K₃TaF₈; 1039 K) = (52 ± 2) kJ mol⁻¹ and of K₃TaOF₆ at temperature of fusion 1055 K: Δ_fusH_m(K₃TaOF₆; 1055 K) = (62 ± 3) kJ mol⁻¹ have been determined.     

Novel solvent-free reaction of C60 with active methylene compounds in the presence of Na2CO3 under high-speed vibration milling

Inorganic base, Na₂CO₃, was utilized to replace organic base, DBU, in the Bingel reaction employing diethyl bromomalonate under the mechanochemical ‘high-speed vibration milling’ conditions to give the cyclopropanated C₆₀1 in high yield. In contrast, reactions of C₆₀ with diethyl malonate and ethyl acetoacetate in the presence of Na₂CO₃ under HSVM conditions afforded 1,4-bisadduct 2 and dihydrofuran-fused C₆₀ derivative 3, respectively.     

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.     

Isolated spin 3/2 plaquettes in Na3RuO4

The crystal structure of Na₃RuO₄ determined by powder neutron diffraction is reported. The structure consists of isolated tetramers of edge sharing RuO₆ octahedra in the ab plane, creating isolated four-member plaquettes of Ru atoms comprised of two equilateral triangles sharing an edge. Magnetic susceptibility measurements reveal an antiferromagnetic transition at ∼29 K, with . Neutron diffraction data indicate the onset of three-dimensional magnetic ordering at 29 K.     

The crystal structure determinations and refinements of K2S2O7, KNaS2O7 and Na2S2O7 from X-ray powder and single crystal diffraction data

The crystal structures of K₂S₂O₇, KNaS₂O₇ and Na₂S₂O₇ have been solved and/or refined from X-ray synchrotron powder diffraction data and conventional single-crystal data. K₂S₂O₇: From powder diffraction data, monoclinic C2/c, Z=4, a=12.3653(2), b=7.3122(1), , β=93.0792(7)°, R_Bragg=0.096. KNaS₂O₇: From powder diffraction data; triclinic , Z=2, a=5.90476(9), b=7.2008(1), , α=101.7074(9), β=90.6960(7), γ=94.2403(9)°, R_Bragg=0.075. Na₂S₂O₇: From single-crystal data; triclinic , Z=2, a=6.7702(9), b=6.7975(10), , α=116.779(2), β=96.089(3), γ=84.000(3)°, R_F=0.033. The disulphate anions are essentially eclipsed. All three structures can be described as dichromate-like, where the alkali cations coordinate oxygens of the isolated disulphate groups in three-dimensional networks. The K-O and Na-O coordinations were determined from electron density topology and coordination geometry. The three structures have a cation-disulphate chain in common. In K₂S₂O₇ and Na₂S₂O₇ the neighbouring chains are antiparallel, while in KNaS₂O₇ the chains are parallel. The differences between the K₂S₂O₇ and Na₂S₂O₇ structures, with double-, respectively single-sided chain connections and straight, respectively, corrugated structural layers can be understood in terms of the differences in size and coordinating ability of the cations.     

K3Na(FeO4)2的电合成及其晶体结构

本文采用间接法电合成出较高纯度的复盐K₃Na(FeO₄)₂晶体，用粉末XRD结构分析法对其晶体结构作了详细研究。用EDX和AAS确认了其化学式。结构分析表明，K₃Na(FeO₄)₂晶体属三方晶系，具有六方晶胞，空间群为P3m1(No.164)，Z=1,晶胞中有6个O位于6(i)位，O,Fe和K各自有2个位于2(d)位，1个K和Na分别位于1(b)位和1(a)位，晶胞参数a=0.583 3(1) nm,c=0.755 9(1) nm，D=2.824 g·cm^-3。同时晶胞中各原子间化学键键长得到确定。     

K2CO3含量对Ni-Cu-Mn-K/Al2O3水煤气变换催化剂结构和性能的影响

以γ-Al₂O₃为载体，采用等体积浸渍法，制备了不同K₂CO₃含量的Ni-Cu-Mn-K/Al₂O₃水煤气变换催化剂，采用低温N₂吸附、XRD、TPD和TPR，考察了K₂CO₃含量对催化剂结构和性能的影响。结果表明:K₂CO₃的加入使催化剂的还原温度有所提高，适量的K₂CO₃能增加活性组分的电子密度，从而增强其给电子活化CO的能力，提高催化剂的活性。但过量的K₂CO₃使得催化剂比表面积和孔容降低，且导致催化剂对CO吸附过强，催化活性降低。当Ni-Cu-Mn-K/γ-Al₂O₃催化剂中K₂CO₃的添加量为7.5%时，且催化剂经530 ℃耐热15 h后，在350 ℃时水煤气变换反应中CO转化率达62.29%。     

K2Mo4O13 phases prepared by hydrothermal synthesis

Hydrothermal synthesis in the K-Mo oxide system was investigated as a function of the pH of the reaction medium. Four compounds were formed, including two K₂Mo₄O₁₃ phases. One is a new low-temperature polymorph, which crystallizes in the orthorhombic, space group Pbca, with Z=8 and unit cell dimensions a=7.544(1) Å, b=15.394(2) Å, c=18.568(3) Å. The other is the known triclinic K₂Mo₄O₁₃, whose structure was re-determined from single crystal data; its cell parameters were determined as a=7.976(2) Å, b=8.345(2) Å, c=10.017(2) Å, α=107.104(3)°, β=102.885(3)°, γ=109.760(3)°, which are the standard settings of the crystal lattice. The orthorhombic phase converts endothermically into triclinic phase at ca. 730 K with a heat of transition of 8.31 kJ/mol.     

Determination of dissociation degrees of K3NbF8 and K3TaF8 by thermodynamic analysis of subsystems of the KF-K2NbF7 and KF-K2TaF7 systems

A special form of the LeChatelier-Shreder equation describing the equilibrium between the crystalline phase and the melt in system A-AB in which the substance AB partially dissociates upon melting was applied to systems KF-K₃NbF₈, K₂NbF₇-K₃NbF₈ and to KF-K₃TaF₈, K₂TaF₇-K₃TaF₈ subsystems of the binary systems KF-K₂NbF₇ and KF-K₂TaF₇ in which the additive compounds K₃NbF₈ and K₃TaF₈ are formed. Using the phase diagram of the system KF-K₂NbF₇ determined by McCawley and Barclay (1971) and the values of the fusion enthalpy of K₃NbF₈ taken from literature, the intervals of the dissociation degree values of K₃NbF₈ for both branches of the liquidus curve of K₃NbF₈ were calculated. The calculated values of the dissociation degree depend on the coordinates of the liquidus curve of K₃NbF₈ of the pertinent phase diagram, on its used branch and section, and on the value of the fusion enthalpy of K₃NbF₈. For the measured fusion enthalpy of K₃NbF₈ (57 kJ mol⁻¹), a common interval of the dissociation degree values of K₃NbF₈ for both branches of the liquidus curve of K₃NbF₈ is 0.71–0.72. Similarly, intervals of the dissociation degree values of K₃TaF₈ for both branches of the liquidus curve of K₃TaF₈ were calculated using the phase diagram of the system KF-K₂TaF₇ determined by Boča et al. (2007) and the measured fusion enthalpy of K₃TaF₈ ((52 ± 2) kJ mol⁻¹). The error of the determination of the fusion enthalpy of K₃TaF₈, the common interval of the dissociation degree values of K₃TaF₈ for both branches of the liquidus curve of K₃TaF₈ is 0.68–0.69.     

Raman spectroscopic study of K3H(SO4)2 (phases I and II) single crystals

A Raman study of K₃H(SO₄)₂ as a function of temperature reveals that this compound undergoes a phase transition at T_c = 483 K prior to the decomposition at 508 K.     

Carbon coated Na3V2(PO4)3 as novel electrode material for sodium ion batteries

A Na₃V₂(PO₄)₃ sample coated uniformly with a layer of 6 nm carbon has been successfully synthesized by a one-step solid state reaction. This material shows two flat voltage plateaus at 3.4 V vs. Na⁺/Na and 1.63 V vs. Na⁺/Na in a nonaqueous sodium cell. When the Na₃V₂(PO₄)₃/C sample is tested as a cathode in a voltage range of 2.7-3.8 V vs. Na⁺/Na, its initial charge and discharge capacities are 98.6 and 93 mAh/g. The capacity retention of 99% can be achieved after 10 cycles. The electrode shows good cycle performance and moderate rate performance. When it is tested as an anode in a voltage range of 1.0-3.0 V vs. Na⁺/Na, the initial reversible capacity is 66.3 mAh/g and the capacity of 59 mAh/g can be maintained after 50 cycles. These preliminary results indicate that Na₃V₂(PO₄)₃/C is a new promising material for sodium ion batteries.     

Thermoelectric properties and microstructure of Mg3Sb2

Mg₃Sb₂ has been prepared by direct reaction of the elements. Powder X-ray diffraction, thermal gravimetric, differential scanning calorimetery, and microprobe data were obtained on hot pressed samples. Single phase samples of Mg₃Sb₂ were prepared and found to contain oxygen at the grain boundaries and to lose Mg and oxidize at temperatures above 900 K. Thermoelectric properties were characterized by Seebeck, electrical resistivity, and thermal conductivity measurements from 300 to 1023 K, and the maximum zT was found to be 0.21 at ∼875 K.     

Cr掺杂对K2La2Ti3O10光催化活性的影响

通过溶胶-凝胶法制备了层状钙钛矿结构的K₂La₂Ti₃O₁₀及Cr掺杂的K₂La₂Ti₃O₁₀，采用X-射线衍射(XRD)、紫外可见漫反射光谱(DRS)、X射线光电子能谱(XPS)等对K₂La₂Ti₃O₁₀及Cr掺杂K₂La₂Ti₃O₁₀进行了表征。以I^-为电子给体、分别在紫外和可见光辐射下研究了K₂La₂Ti₃O₁₀及Cr掺杂K₂La₂Ti₃O₁₀光催化分解水的产氢活性。采用第一性原理，计算了Cr掺杂对K₂La₂Ti₃O₁₀半导体能带结构和态密度的影响，从电子结构的变化揭示了掺杂引起光催化活性差异的原因。结果表明，Cr的掺入能够改善和提高K₂La₂Ti₃O₁₀的光解水的产氢活性；Cr改善和提高K₂La₂Ti₃O₁₀的光解水的产氢活性存在一个最佳的掺杂浓度；当Cr与Ti的物质量的比为0.02∶1时，紫外光催化分解水产氢速率为1 500 μmol·L^-1·h^-1，可见光催化分解水产氢速率为83.6 μmol·L^-1·h^-1，分别为K₂La₂Ti₃O₁₀掺杂改性前产氢速率的26和5倍。     

Phase transitions in K3AlF6

Phase transitions in the elpasolite-type K₃AlF₆ complex fluoride were investigated using differential scanning calorimetry, electron diffraction and X-ray powder diffraction. Three phase transitions were identified with critical temperatures , and . The α-K₃AlF₆ phase is stable below T₁ and crystallizes in a monoclinic unit cell with a=18.8588(2)Å, b=34.0278(2)Å, c=18.9231(1)Å, β=90.453(1)° (a=2a_c−c_c, b=4b_c, c=a_c+2c_c; a_c, b_c, c_c—the basic lattice vectors of the face-centered cubic elpasolite structure) and space group I2/a or Ia. The intermediate β phase exists only in very narrow temperature interval between T₁ and T₂. The γ polymorph is stable in the T₂<T<T₃ temperature range and has an orthorhombic unit cell with a=36.1229(6)Å, b=17.1114(3)Å, c=12.0502(3)Å (a=3a_c−3c_c, b=2b_c, c=a_c+c_c) at 250 °C and space group Fddd. Above T₃ the cubic δ polymorph forms with a_c=8.5786(4)Å at 400 °C and space group . The similarity between the K₃AlF₆ and K₃MoO₃F₃ compounds is discussed.     

A new one-pot synthesis of Gb3 and isoGb3 trisaccharide analogues

Gb₃ and isoGb₃ are both biologically important oligosaccharides. A new efficient synthesis of Gb₃ and isoGb₃ trisaccharide analogues has been achieved by one-pot sequential glycosylation strategy starting from simple monosaccharide building blocks promoted by N-(phenylthio)-?-caprolactam at room temperature.     

K2FeO4的合成及对含苯酚水溶液中重金属离子的去除性能

以次氯酸钙和九水硝酸铁为原料采用湿化学法合成K₂FeO₄,X射线衍射（XRD）、扫描电子显微镜（SEM）、红外吸收光谱（FTIR）、能量色散谱（EDS）的对比分析表明通过二次重结晶纯化可有效去除粗产品中的杂质,获得纯度更高、晶形更完整的K₂FeO₄晶体。同时研究了K₂FeO₄投加量、时间、溶液pH值、温度、初始离子浓度等因素下,K₂FeO₄对含苯酚水溶液中的Cu（Ⅱ）、Cd（Ⅱ）的去除性能,并通过扫描电子显微分析（SEM）、能量色散谱（EDS）、红外吸收光谱（FTIR）等方法研究了K₂FeO₄对溶液中重金属离子的去除机理。实验结果表明：K₂FeO₄可通过一步反应同时去除溶液中的Cu（Ⅱ）、Cd（Ⅱ）以及苯酚,K₂FeO₄主要通过吸附、共沉淀和表面配位的方式去除溶液中的重金属离子。     

K2FeO4的合成及对含苯酚水溶液中重金属离子的去除性能

以次氯酸钙和九水硝酸铁为原料采用湿化学法合成K₂FeO₄,X射线衍射（XRD）、扫描电子显微镜（SEM）、红外吸收光谱（FTIR）、能量色散谱（EDS）的对比分析表明通过二次重结晶纯化可有效去除粗产品中的杂质,获得纯度更高、晶形更完整的K₂FeO₄晶体。同时研究了K₂FeO₄投加量、时间、溶液pH值、温度、初始离子浓度等因素下,K₂FeO₄对含苯酚水溶液中的Cu（Ⅱ）、Cd（Ⅱ）的去除性能,并通过扫描电子显微分析（SEM）、能量色散谱（EDS）、红外吸收光谱（FTIR）等方法研究了K₂FeO₄对溶液中重金属离子的去除机理。实验结果表明：K₂FeO₄可通过一步反应同时去除溶液中的Cu（Ⅱ）、Cd（Ⅱ）以及苯酚,K₂FeO₄主要通过吸附、共沉淀和表面配位的方式去除溶液中的重金属离子。     

Structural modulation in K2V3O8

To elucidate the phase transition at 115 K in the fresnoite-type compound K₂V₃O₈, we undertook temperature-dependent neutron powder diffraction and single-crystal X-ray diffraction (XRD). For structure refinements in the nominal space group P4bm, the most dramatic change is evidenced by the a cell edge, which initially expands on cooling, then abruptly begins to contract at 115 K. The c cell edge contracts monotonically. The atomic displacement parameters (ADPs) also deviate from their expected temperature dependence at 115 K, where the oxygen atoms in the vanadium oxide plane exhibit an increase in apparent positional disorder. Similar changes in lattice parameters and ADPs are observed from the single-crystal XRD refinements. Below 115 K, weak superlattice reflections are clearly evident in XRD patterns recorded by a CCD detector, and these extra reflections can be indexed with the wave vector ±1/3〈110〉*+1/2c*. Possible space groups for the modulated structure are P4₂bc and P4nc.     

Synthesis, structure and properties of the new rare-earth Zintl phase Yb11GaSb9

A new rare-earth rich Zintl phase Yb₁₁GaSb₉ was synthesized by direct fusion of the corresponding elements, and large single crystals of the compound were obtained from high temperature flux synthesis. Its crystal structure was determined by single-crystal X-ray diffraction to be orthorhombic in the non-centrosymmetric space group Iba2 (No. 45), Z=4 (R₁=3.24%, wR₂=6.40%) with , , measured at 90(3) K. The structure belongs to the Ca₁₁InSb₉-type and can be viewed as built of isolated Sb₄-tetrahedra centered by Ga, Sb-dimers and isolated Sb anions, which are separated by Yb²⁺ cations. Electron count according to the Zintl formalism suggests that the phase is electron-precise and charge-balanced, which is supported by the virtually temperature-independent magnetization for Yb₁₁GaSb₉. Electrical resistivity data from 2 to 400 K confirm that Yb₁₁GaSb₉ is a small band-gap semiconductor with room temperature resistivity , and low-temperature resistivity at 2 K . As such, Yb₁₁GaSb₉ and related compounds might be promising materials for thermoelectric applications, and currently, efforts to synthesize new members of this family and test their thermoelectric performance are under way.