Dynamic disorder in ammonium oxofluorotungstates (NH4)2WO2F4 and (NH4)3WO3F3

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.     

The nature and the mechanism of ion transfer in tungstates Me2+{WO4} (Ca, Sr, Ba) and Me 2 3+ {WO4}3 (Al, Sc, In) according to the data acquired by the tubandt method

The Tubandt method of electrolysis is used for studying the nature of ionic carriers in ceramics of tungstates Me²⁺{WO₄} (Ca, Sr, Ba) and Me ₂ ³⁺ {WO₄}₃ (Al, Sc, In) which are solid electrolytes. These compounds have the salt-like islet structure with isolated tetrahedrons {WO ₄ ^2? } and are crystallized in the allied structural types of scheelite (CaWO₄) for Me²⁺ and Sc tungstate (Sc₂{WO₄}₃) for Me³⁺. The electrolysis is carried out in 2- or 3-section cells (?)Pt|M ₂ ^n/n+ {WO₄}|Me ₂ ^n/n+ {WO₄}|Pt(+) in air atmosphere at the temperature of ～900°C and cell voltage of 4 and 300 V. All experiments without exception demonstrate a decrease in the mass of the cathodic section of cells. This points to the negative charge of ionic mass carriers and their transfer towards the Pt⁽⁺⁾ electrode. The cathodic briquette mass loss Δm ^(?) depends linearly on the charge passed through a cell. In all experiments with MeWO₄ tungstates, the anodic disk mass remains constant. The electrolysis of Me₂(WO₄)₃ cells is always accompanied by an increase in the anolyte mass Δm ⁽⁺⁾; however, in all experiments, Δm ^(?) > Δm ⁽⁺⁾. All data on mass variation and the results of studying the composition of nearelectrode electrolyte layers by XRD and SEM methods correspond to the condition $t_{WO_4^{2 - } } > t_C $ (C is the cation), i.e., {WO ₄ ^2? } anions pertain to the major ionic carriers. The transport number $t_{WO_4^{2 - } } $ is calculated based on the Faraday law from Δm ^(?). It is shown that the second ionic carrier with the mobility even higher than that of {WO ₄ ^2? } is the O^2? ion. For middle values of transport numbers, their ratio is shown to be $t_{O^{2 - } } $ (0.5–0.8) > (0.2–0.5) $t_{WO_4^{2 - } } $ . No results that would confirm the involvement of Me²⁺ and Me³⁺ ions in conduction are obtained.     

Ein neuer Strukturtyp am Lanthanoid-Oxowolframat FeCe(WO4)W2O8 = FeCe(WO4)3

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.     

WO3纳米材料的H2S气敏特性

用于检测微量H2S气体的SnO2元件具有相当高的灵敏度,但响应—恢复时间较长,选择性的提高也受限制。本文用化学沉淀法合成了xwt.%SiO2-WO3(x=0,3,5,10,15)纳米粉体,研制出一系列烧结型气敏元件,工作温度为180℃,掺杂量为5％的气敏元件对H2S有很高的灵敏度和选择性,响应—恢复快,而且工作温度较低,有较好的应用价值。     

Metallampullen als Mini‐Autoklaven: Synthese und Kristallstrukturen der Ammoniakate [Al(NH3)4Cl2][Al(NH3)2Cl4] und (NH4)2[Al(NH3)4Cl2][Al(NH3)2Cl4]Cl2

Metal Ampoules as Mini‐Autoclaves: Syntheses and Crystal Structures of [Al(NH₃)₄Cl₂][Al(NH₃)₂Cl₄] and (NH₄)₂[Al(NH₃)₄Cl₂][Al(NH₃)₂Cl₄]Cl₂ The salts [Al(NH₃)₄Cl₂]⁺[Al(NH₃)₂Cl₄]^–≡AlCl₃ · 3 NH₃ ( 1 ) and (NH₄⁺)²[Al(NH₃)₄Cl₂]⁺[Al(NH₃)₂Cl₄]^–(Cl^–)₂≡ AlCl₃ · 3 NH₃ · (NH₄)Cl ( 2 ) have been obtained as single crystals during the reactions of aluminum and aluminum trichloride, respectively, with ammonium chloride in sealed Monel metal containers. The crystal structure of 1 was determined again [triclinic, P‐1; a = 574.16(10); b = 655.67(12); c = 954.80(16) pm; α = 86.41(2); β = 87.16(2); γ = 84.89(2)°], that of 2 for the first time [monoclinic, I2/m; a = 657.74(12); b = 1103.01(14); c = 1358.1(3) pm; β = 103.24(2)°].     

Conductivity of composite materials based on Me2(WO4)3 and WO3 (Me = Sc,In)

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 σ_tot and σ_el are assessed by the $\sigma (a_{O_2 } )$ and EMF methods. The concentration dependences of conductivity and activation energy are plotted based on the σ_tot and σ_ion 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 {Me^IIWO₄ · 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.     

Visible-light-induced degradation of rhodamine B by nanosized Bi2WO6

Visible-light-induced photodegradation of rhodamine B over nanosized Bi2WO6 has been observed. Bi2WO6 exhibited a high photoactivity to photodegrade rhodamine B in the central pH solution under visible irradiation (lambda > 420 nm). After five recycles for the photodegradation of rhodamine B, the catalyst did not exhibit any significant loss of activity, confirming the photocatalyst is essentially stable. The total organic carbon measurement displayed that a high degree of mineralization was achieved in the present photochemical system. The results of density functional theory calculation illuminated that the visible-light absorption band in the Bi2WO6 catalyst is attributed to the band transition from the hybrid orbitals of Bi6s and O2p to the W5d orbitals. The Bi2WO6-assisted photocatalytic degradation of rhodamine occurs via two competitive processes: a photocatalytic process and a photosensitized process. The transformation of rhodamine is mainly via the photocatalytic process. Kinetic studies by using electron spin resonance and the radical scavenger technologies suggest that *OH is not the dominant photooxidant. Direct hole transfers and O2*- could take part in Bi2WO6 photocatalysis. This study provided a possible treatment approach for organic pollutants by using visible light in aqueous ecosystems.     

Peculiar transformation of a nonaromatic Al(4)Cl(4)(NH(3))(4) into an aromatic Na(2)Al(4)Cl(4)(NH(3))(4)

We analyzed the molecular orbitals for a Al(4)Cl(4)(NH(3))(4) compound, which is a model of the (AlBr x NEt(3))(4) crystal structure recently reported by Schn?ckel and co-workers. We found that even though Al(4)Cl(4)(NH(3))(4) contains a planar square Al(4) cluster it is not an aromatic compound. However, the addition of two sodium atoms to Al(4)Cl(4)(NH(3))(4) yields a new Na(2)Al(4)Cl(4)(NH(3))(4) compound which is a pi-aromatic molecule. We hope that prediction of this new compound will facilitate a synthesis of aluminum aromatic solids.     

液相法制取Y_2(WO_4)_3的工艺探讨及其负热膨胀性能比较

采用液相共沉淀法成功合成Y2(WO4)3,利用高、低温X射线衍射方法研究Y2(WO4)3的结构及其负热膨胀性能,发现液相共沉淀法制得的Y2(WO4)3与固相反应法制得的Y2(WO4)3具有一致的Pnca空间群正交结构和相差不大的晶胞参数和体积(经TOPAS软件计算),二者的本征体热膨胀系数分别为-18.8×10-6℃-1(液相法)和-19.5×10-6℃-1(固相法)。液相共沉淀法相对传统固相化学反应法,具有减少合成循环次数和降低反应温度的优点。这证明该法制备稀土钨酸盐类负膨胀材料是可行的。     

Calculation of ligand-field and Stark sub-levels in laser crystals Nd~(3+):KY(WO_4)_2 and Nd~(3+):KGd(WO_4)_2

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.     

体系酸度对直接沉淀法合成钛酸钡的影响

钛酸钡是一种典型的具有钙钛矿型结构的电子陶瓷材料,具有优良的铁电、介电、压电与热释电、以及线性电光效应和非线性光学效应等特点,使其在现代电子技术与光电子技术领域获得了广泛的应用.     

纳米氧化铝对贵金属Pd(Ⅱ)的吸附性能研究

采用火焰原子吸收法为检测手段,以纳米氧化铝为吸附剂,系统地研究了其在静态条件下对贵金属离子Pd(Ⅱ)的吸附性能,确定了最佳吸附及解脱条件。实验结果表明,在pH 5.0条件下,试液中的痕量钯可被定量吸附,用0.1mol/L HCl-30 g/L硫脲溶液可将吸附的钯离子完全解脱。对合成样进行测定,钯的回收率在95.0%以上。     

Glass formation in the systems Al2(SO4)3-MSO4-H2O (M = Cd2+, Zn2+, Mg2+) and Al2(SO4)3-Fe2(SO4)3-H2O

The glass formation region boundaries were found in the systems Al₂(SO₄)₃-MSO₄-H₂O, where M = Cd²⁺, Zn²⁺, and Mg²⁺, and Al₂(SO₄)₃-Fe₂(SO₄)₃-H₂O. The causes of the differences in glass-forming ability between the studied systems were analyzed. The structures and properties of glassy Al₂(SO₄)₃ · 11H₂O and Fe₂(SO₄)₃ · 11H₂O were compared.     

掺杂合成纳米WO3

掺杂SiO2的WO3粉体对NOX、NH3等多种气体十分敏感,可用于某些特定场合和环境监测方面[1,2]。本文以钨酸铵和硅酸乙酯为原料,分别采用固相法和沉淀法制备了不同掺杂量的SiO2 WO3纳米粉体,并对其进行了XRD,TEM表征。1　实验部分1 1　仪器与试剂德国布鲁克D8X 射线衍射仪;日本电子公司JEM 100SX型透射电子显微镜;天津卫东电炉厂RJX 5 13型马弗炉;上海司乐仪器厂85-2型恒温磁力搅拌器。钨酸铵(NH4)5H5[H2(WO4)6]H2O(化学纯);硅酸乙酯(C2H5O)4Si(分析纯);无水乙醇CH3CH2OH(分析纯);盐酸HCl(分析纯)。1 2　固相法制备WO3…     

On the preparation and thermal stability of (NH4)3 VOF6.1.5H2O and (NH4)3NbOF6.1.5H2O

(NH₄)₃VOF₆ and (NH₄)₃NbOF₆ were prepared by a simple solid state route and their thermolysis studied. It is concluded that both these compounds have water of hydration, their structures are different and they show first order phase transitions.     

Glass formation in the Al(IO3)3-Al2(SO4)3-H2O system

Glass-formation boundaries in the Al(IO₃)₃-Al₂(SO₄)₃-H₂O system are determined. The IR spectra of glassy and crystalline Al(IO₃)₃ · 8H₂O samples are measured. The structure and properties of glassy Al(IO₃)₃ · 10H₂O are compared to those of glassy Al₂(SO₄)₃ · 10H₂O.