New protonic solid electrolyte with tetragonal tungsten bronze structure obtained through ionic exchange

Proton exchange reactions have been performed on tetragonal tungsten bronze-like NaNbWO₆ by using nitric acid as an exchanging agent. The characterization of the exchange reaction products has been made by means of chemical analysis, X-ray diffraction, thermal analysis, and IR spectroscopy. The exchange reaction takes place topotactically and the following formula is proposed for the obtained phase of variable composition: Na_1−xH_xNbWO₆·yH₂O (0<x?0.46 and 0?y?0.12). Impedance spectroscopy on the present proton exchanged samples indicated that these samples behaved as solid electrolytes under high humidity. As an example, the compound with the composition Na_0.68H_0.32NbWO₆·0.1 H₂O exhibits ionic conductivity of 8×10⁻³ and 1×10⁻² S cm⁻¹ at 70°C and 90°C, respectively.     

硝酸根离子介质中偏钛酸钡的水热合成

以硝酸和钛酸四丁酯为原料，在２４０℃的碱液中成功地制备了四方相ＢａＴｉＯ３运用ＸＲＤ、ＤＳＣ和ＩＲ等技术碱度、硝酸根离子、钛源活性、填充度等因素对ＢａＴｉＯ３形成、粒度和物相的作用，ＫＯＨ最适宜浓度为１．０ｍｏｌ／Ｌ，碱液中ＢａＴｉＯ３是ＢａＯ－ＴｉＯ２体系中最稳定的物相，硝酸根离子参与了ＢａＴｉＯ３晶体的成核和生长，钛源的高活性和高填充度有利于四方ＢａＴｉＯ３的形成。     

Hydrothermal synthesis and phase stability of Pb stabilized ZrO2 nanoparticles

The Pb doped metastable tetragonal ZrO₂ (t-ZrO₂:Pb) nanoparticles have been successfully synthesized by hydrothermal method. Pb ion doping has great effects on the phases, crystallite sizes and optical band gaps. Systematic structural characterization revealed that the introduction of Pb ion results in lattice expansion. The as-prepared t-ZrO₂:Pb with ca 4–6 nm in size has high specific surface area (>150 m²/g) and narrow particle size distributions. The diffuse reflectance spectra investigated that the band gap shifts from ultraviolet (E_g = 5.19 eV) for pure ZrO₂ to the visible region for t-ZrO₂:Pb and the gap can be effectively adjusted with the content of Pb in nanocrystals. Through thermal treatment, Pb ion doped in ZrO₂ crystals was excluded with increasing temperature. At 800 °C, the three t-ZrO₂:Pb samples of ZPO-2, ZPO-3 and ZPO-4 still contained the pure tetragonal phase, in which Pb content were not reduced to zero, while the transformation from tetragonal to monoclinic phase occurred due to zero Pb content in ZPO-1. The reason to this transformation and stabilized mechanism of Pb ion in ZrO₂ were discussed.     

Alkylation of catechol with methanol to guaiacol over sulphate-modified zirconia solid acid catalysts

A series of sulphate-promoted ZrO₂ solid acid catalysts with different contents of SO₄ ²⁻ were calcined at 450°C in air for 4 h and tested for the liquid-phase alkylation of catechol to guaiacol in a fixed-bed down-flow reactor. The 5 wt.% SO₄ ²⁻ on ZrO₂ showed the best conversion (82%) and selectivity for guaiacol (84%) at 200°C and 1 bar pressure. A smooth correlation was observed between the catalytical activity and surface acidity of sulphated zirconia. Based on our results, a surface mechanism is proposed.     

Spectroscopic Studies of a Three-dimensional, Five-coordinated Copper(Ⅱ) Complex via Hydrogen Bonds: [Cu(PDA)(H_2O)_2](H_2PDA=Pyridine-2,6-dicarboxylic Acid)

IntroductionFive- coordinated complexes with d9- configuredcations have received much attention stereochemi-cally,spectrochemically and biologically,and havebeen comprehensively discussed[1] . Usually thereare two stable configurations for the copper( )complexes with five equal coordinating atoms:anapically elongated square pyramid( SP) and a com-pressed trigonal bipyramid( TBP) ,with an obviousenergetic preference for the latter coordination.When the ligands are rigid and provide angular d…     

Analysis of silica fume produced by zircon desilication

Novel chemical methods have been developed to allow for the determination of the components of silica fume produced by zircon desilication. Hitherto, no methods have been described for the analysis of this material. The amorphous silica is first removed by treatment with sodium hydroxide. The residue from the hydroxide treatment may then be subjected to a suite of reagents to determine the zircon, the total zirconia, the monoclinic zirconia and the tetragonal zirconia content of the fume. The zircon content of the fume is determined by treatment of the hydroxide residue with concentrated hydrofluoric acid (HF). The total zirconia content of the fume is determined by digestion of the hydroxide residue with fuming sulphuric acid (oleum), while the relative amounts of monoclinic and tetragonal zirconia may be found by treatment of the hydroxide residue with 10%w/v HF, which attacks the less stable tetragonal phase. Both X-ray diffraction and particle size analysis were used to validate the steps in the analytical procedure. An explanation of the presence of tetragonal zirconia in the fume is proposed. A greater understanding of the composition of the fume led to the installation of a separator in the company's production line to remove the zircon. Australian Fused Materials (AFM) now produces a vastly superior grade of fume marketed under the code SF-98.     

New high permittivity tetragonal tungsten bronze dielectrics Ba2LaMNb4O15: M=Mn, Fe

The new phases Ba₂LaMNb₄O₁₅: M=Mn, Fe were prepared by solid state reaction at 1100 °C. They have the tetragonal tungsten bronze structure, space group P4/mbm, at room temperature. The two octahedral sites show partial order of M and Nb with preferential occupancy of the smaller B(1) sites by M. Both phases have high permittivities 90±15 over the range 10-320 K. Ba₂LaFeNb₄O₁₅ is highly insulating with bulk conductivity ?10⁻⁸ ohm⁻¹ cm⁻¹ at 25 °C and tan δ?0.001 over the range 100-320 K and at 10⁵ Hz. Solid solutions between these new phases and the compositionally and structurally related relaxor ferroelectric Ba₂LaTi₂Nb₃O₁₅ show gradual loss of ferroelectric behaviour attributed to replacement of polarisable Ti⁴⁺ by a mixture of (Mn, Fe)³⁺ and Nb⁵⁺.     

First findings of monocrystalline aragonite inclusions in garnet from diamond-grade UHPM rocks (Kokchetav Massif, Northern Kazakhstan)

The crystal field effect and microscopic origins of the Zeeman g-factors g(//) and g(⊥) for (6)S(3d(5)) state ions at tetragonal symmetry crystal filed, taking into account the spin-spin (SS), the spin-other-orbit (SOO), and the orbit-orbit (OO) magnetic interactions besides the well-known spin-orbit (SO) magnetic interaction, have been investigated using the microscopic spin Hamiltonian theory and the complete diagonalization method (CDM). It is found that the g(//)(±1/2)≠g(//)(±5/2) and g(⊥)(±1/2)≠g(⊥)(±5/2), where the g-factors g(//)(±1/2) and g(⊥)(±1/2) express the g-factors of the ground state |M?(s)=±1/2), whereas the g-factors g(//)(±5/2) and g(⊥)(±5/2) express the g-factors of the ground state |M?(s)=±5/2). It is shown that although the SO magnetic interaction is the most important one, the contributions to the shifts of g-factors Δg(//)(=2.0023-g(//)) and Δg(⊥)(=2.0023-g(⊥)) from other three magnetic interactions including the SS, SOO, and OO magnetic interactions are appreciable and should not be omitted, especially for the shifts of g-factors Δg(//)(±5/2) and Δg(⊥)(±5/2). The individual contributions to the shifts of g-factors arising from the spin quartet states and spin doublet states have been studied. The investigations show that the Δg(//)(±1/2) and Δg(⊥)(±1/2) primarily result from the spin quartet states, whereas Δg(//)(±5/2) and Δg(⊥)(±5/2) from the spin quartet states as well as the combined effects between the spin quartet states and the spin doublet states. The contribution to the shifts of g-factors from the net spin doublet states is zero.     

Study of the effect of precipitant on the high-temperature phase stability of SrO-ZrO2 prepared by n-butanol soft-template method

SrO doped zirconia (20%) was synthesized by n-butanol soft-template method using both NaOH and ammonia solution as precipitants. The high-temperature phase stability was investigated following further heat treatment at 1000°C for 2 h. XRD and Raman spectra were used to characterize the crystal form of zirconia. In addition, TEM was used to characterize the dispersibility of SrO doped zirconia. The results indicated that the concentration of OH^? introduced into the ZrO₂ lattice was the main factor controlling the crystal form of nanosized zirconia. The NaOH solution precipitant could improve the dispersibility of SrO doped t-ZrO₂, and could also prevent the phase transformation of zirconia from t-ZrO₂ to m-ZrO₂ effectively.