Dynamics of the proton transport in the Cs5H3(SO4)4 · xH2O superionic conductor (PCHS)

The article summarizes selected properties of Cs₅H₃(SO₄)₄ · xH₂O related to the proton transport. The dynamics of the proton transport in all known phases is discussed and a consistent microscopic model of the transition into the glassy state is proposed. Paper presented at the 3rd Euroconference on Solid State Ionics in Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Evidence for a quasi-two-dimensional proton glass state in Cs5H3(SO4)(4); xH(2)O Crystals

We describe damping of hypersonic and ultrasonic longitudinal acoustic (LA) phonons in crystals of Cs 5H (3)(SO (4))(4);xH 2O (PCHS) between 100 and 360 K. The damping of LA phonons exhibits strong dispersion caused by relaxation processes in the region of transformation into the glasslike phase (T(g) approximately 260 K). Near T(g) the damping of ultrasonic phonons propagating in the basal plane reflects the cooperative freezing of acid protons. The damping of LA phonons propagating perpendicular to the basal plane can be fit by the Debye model and is due to the interaction between protons and LA phonons. This suggests that the proton glass state that is realized at T相似文献   

Ionic motion in the defect pyrochlore NH4TaWO6

Measurement of both spin-lattice and spin-spin relaxation time for protons in NH₄TaWO₆ suggest rapid ionic motion in this compound. Analysis of the data gives an activation energy of ～0.3 eV and an attempt frequency of ～1×10¹⁰ sec^?1. The data is used to suggest a model for ionic motion which involves movement of individual protons rather than the NH₄⁺ ion.     

Phase diagrams in the proton conductor systems Sr6Ta2O11 × nH2O and Sr5.92Ta2.08O11.12 × nH2O

The systems Sr₆Ta₂O₁₁–H₂O and Sr_5.92Ta_2.08O_11.12–H₂O were investigated. At high temperatures, both compounds are normal proton conductors but at lower temperatures show the formation of hydrate phases (here labelled β-phases). The latter are deleterious if the above compounds were to be used in fuel cells, sensors and pumping devices. The phase diagrams of the 2 systems were determined using thermogravimetry. The solubilities of water vapor in the α-phases were measured. Considering 2-phase mixtures of α and β, the plateau vapor pressures were determined as well as the pertinent thermodynamic parameters. The α→α + β solvus was also investigated. The present study complements recent work [I. Animitsa, A. Nieman, A. Sharafutdinov, S. Nochrin, Solid State Ionics 136–137 (2000) 265; I. Animitsa, A. Nieman, S. Titova, N. Kochetova, E. Isaeva, A. Sharafutdinov, N. Timofeeva, Ph. Colomban, Solid State Ionics 156 (2003) 95].     

NMR observation of rattling phonons in the pyrochlore superconductor KOs2O6

We report nuclear magnetic resonance studies on the beta-pyrochlore oxide superconductor KOs2O6. The nuclear relaxation at the K sites is entirely caused by fluctuations of the electric field gradient, which we ascribe to highly anharmonic low frequency oscillation (rattling) of K ions. A phenomenological analysis shows a crossover from overdamped to underdamped behavior of the rattling phonons with decreasing temperature and its sudden sharpening below the superconducting transition temperature T(c). Suppression of the Hebel-Slichter peak in the relaxation rate at the O sites below T(c) also indicates strong electron-phonon coupling.     

Evidence for charged critical behavior in the pyrochlore superconductor RbOs2O6

We analyze magnetic penetration depth (lambda) data of the recently discovered superconducting pyrochlore oxide RbOs(2)O(6). Our results strongly suggest that in RbOs(2)O(6) charged critical fluctuations dominate the temperature dependence of lambda near T(c). This is in contrast with the mean-field behavior observed in conventional superconductors and the uncharged critical behavior found in nearly optimally doped cuprate superconductors. However, this finding agrees with the theoretical predictions for charged criticality and the charged criticality observed in underdoped YBa(2)Cu(3)O(6.59).     

Fast ion conduction in the defect pyrochlore system KBxW2−xO6(B = Al,Ti and Ta)

K⁺ ionic conductivity has been measured by the complex impedence method for the defect pyrochlore type compounds of the general formula K(B^y+_xW⁶⁺_2?x)O₆, (x=1/(6?y)) where B=Al³⁺, Ti⁴⁺ and Ta⁵⁺. Thermogravimetric analysis showed the compounds to be hydrated at room temperature with from ∽0.2 mole for the Al compound to ∽1 mole of water for the Ta substituted phase. There is a correlation between the lattice parameter and amount of water present in the cavities. The ionic conductivity of 5.2×10^?3ω^?1cm^-1 at 300°C for KAl_0.33W_1.67O₆ is found to be best among known KB₂O₆ type pyrochlores. High ionic conductivity has been explained on the basis of occupancy of K⁺ ions in the available sites and polarization of the B₂X₆ network.     

Synthesis and crystallographic studies of garnet-related lithium-ion conductors Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12

High-purity specimens of Li₆CaLa₂Ta₂O₁₂ and Li₆BaLa₂Ta₂O₁₂ have been successfully synthesized by solid-state reactions. The analytical chemical compositions of these samples were in good agreement with the nominal compositions of Li₆CaLa₂Ta₂O₁₂ and Li₆BaLa₂Ta₂O₁₂. The Rietveld refinements verified that these compounds have the garnet-type framework structure with the lattice constants of a = 12.725(2) Å for Li₆CaLa₂Ta₂O₁₂ and a = 13.001(4) Å for Li₆BaLa₂Ta₂O₁₂. All of the diffraction peaks of X-ray powder diffraction patterns were well indexed on the basis of cubic symmetry with space group Ia-3d. To make a search for Li sites, the electron density distributions were precisely examined by using the maximum entropy method. Li⁺ ions occupy partially two types of crystallographic site in these compounds: (i) tetrahedral 24d sites, and (ii) distorted octahedral 96h sites, the latter of which are the vacant sites of the ideal garnet-type structure. The present Li₆CaLa₂Ta₂O₁₂ and Li₆BaLa₂Ta₂O₁₂ samples exhibit the conductivity σ = 2.2 × 10^? 6 S cm^? 1 at 27 °C (E_a = 0.50 eV) and σ = 1.3 × 10^? 5 S cm^? 1 at 25 °C (E_a = 0.44 eV), respectively.     

NMR proton relaxation and chemical exchange in the system H16 2O/H17 2O-[2H6]dimethylsulphoxide

NMR proton relaxation rates of normal and ¹⁷O enriched water in a mixture of 68 mol% water and 32 mol% [²H₆]dimethylsulphoxide were measured for temperatures between 298 K and 183 K. In the range between 240 K and 204 K the limit of fast proton-proton exchange between H¹⁶ ₂O and H¹⁷ ₂O is not obeyed, and relaxation curves deviate from mono-exponential behaviour. By fitting the relaxation curves to a model of NMR two-phase relaxation the proton-proton exchange rate within the aqueous component could be obtained. With decreasing temperature, proton-proton exchange slows down and a residence time of about 125 ms at 215 K is found, but it becomes faster again for still lower temperatures. From the phase-averaged relaxation rates of water in the ¹⁷O enriched mixtures, the ¹⁷O induced proton relaxation rate was derived as a function of temperature. This yields the rotational correlation times of the water molecule in the mixture and the dipolar spin-lattice coupling parameter. The latter is considerably lower than the one predicted from the geometry of water.     

Mn_2[V_(12)B_(16)O_(52)(OH)_6](en)_2(H_3O)_6(H_2O)_5(en=ethylenediamine)的结构及谱学研究

采用水热合成法合成了一种结构新颖的多硼钒氧簇化合物Mn2[V12B16O52(OH)6](en)2(H3O)6(H2O)5(en=ethylenediamine)1,通过单晶X射线衍射确定该化合物的结构。化合物1中,在ab平面上,簇单元之间通过[Mn(H2O)2]2+连接成二维层状结构,另外,层与层之间在c方向上通过氢键连接成三维空间结构。此外,对化合物1的谱学性质进行了红外光谱、磁和热微扰下的二维红外相关光谱、紫外-可见固体漫反射光谱分析,探讨了其结构与谱学性质的关系。磁微扰的二维红外相关光谱表明B—O,V—O—V和Mn—O—B的伸缩振动对于磁场的变化比较敏感,热微扰的二维红外相关光谱表明B—OH,B—O,V—O—V和Mn—O—B的伸缩振动对热微扰比较敏感。     

Infrared Spectra of Morfolonium (mpH)2Mo2Cl6(H20)2(I),(mpH)2Mo2ClxBr6-x(H2O)2(II)/ (mpH)2Mo2Br6(H2O)2(III) and the Pyridinium (PyH)2Mo2I6(H2O)2(IV)Hexahalo-di(aquo): dimolybdate(II) Complexes,Containing Quadruple Metal-Metal Bounds

Abstract

The electronic (800–400 nm), infrared (4000–200,400–20 cm^?1), ordinary Raman (400–200 cm^?1) spectra of morpholinium and the pyridium hexahalo-di(aquo) dimolybdate(II) complexes, containing quadruple metal-metal bonds were investigated. The electronic spectra of the solid compounds at various temperatures (25,100 and 300K) demonstrate intense and structured bands in the visible region (510–582 nm) attributed to the expected δ→δ? transitions.

From the infrared and Raman spectra, the skeletal stretching modes in these complexes have been localized, and the charectenstic bands of these ions were observed in the expected regions.

Finally, the ionic interections were relatively weak, but the existance of phenomena was perceptible and the result was obtained in agreement with X-ray data.     

Dynamics of H2O molecules in ferroelectric K4Fe(CN)6 · 3H2O

The infrared spectrum of potassium ferrocyanide trihydrate has been recorded both in the para and ferroelectric phases. From a combined study of the IR and Raman spectra, it is concluded that there are two sets of water molecules present in the lattice, one set being involved in stronger hydrogen bonding than the other. The ferroelectric transition appears to be associated with an ordering of the water dipoles.     

[Fe3O(Ala)6(H2O)3](ClO4)7和[Fe3O(Gly)6(H2O3)(NO3)7)·3H2O]顺磁共振谱及变温磁化率研究

本文通过对[Fe 3O(Ala) 6(H 2O) 3](ClO 4) 7和[Fe 3O(Gly) 6(H 2O) 3](NO 3) 7·3H 2O的ESR谱的解析及变温磁化率的研究,得出它们的ESR谱具有各向同性的特点;朗德因子分别为2.019和1.997;两种配合物中铁离子间有反铁磁相互作用.     

Adsorption and solution of H2, D2, N2, O2 and CO by (100) Ta

Sticking coefficients, saturation densities, and solution rates of gases on (100) Ta are obtained by comparing with results on (100) W using Auger electron spectroscopy and flash desorption. Hydrogen has a lower sticking coefficient on (100) Ta than on polycrystalline Ta, but solution occurs readily even at 78°K. Differences between H₂ and D₂ are observed for both adsorption and solution. Nitrogen is confined to the surface of Ta for T < ≈500°K, and adsorbed nitrogen dissolves with an activation energy of ≈2.5 kcal mole^?1 upon heating to higher temperatures. The saturation density of O₂ at 300° K is approximately twice that on (100) W. The first monolayer dissolves at ≈500°K but the second dissolves or desorbs only at much higher temperatures. Carbon monoxide adsorbs without solution of either species at 300°K. At ≈500°K carbon dissolves completely leaving oxygen which desorbs at much higher temperature.     

EPR of Mn2+ in single crystals of [Zn(H2O)6]SnF6 and [Co(H2O)6]SnF6; Co2+ spin-lattice relaxation time

EPR studies have been carried out in Mn²⁺-doped single crystals of [M(H₂O)₆]SnF₆ (M  Zn, Co) at different temperatures using X-band microwave frequency. Mn²⁺ has been found to substitute for Zn²⁺ or Co²⁺ exhibiting a unique magnetic complex with z-axis directed long the c-axis of the crystals. Observation of resolved Mn²⁺ spectrum in [Co(H₂O)₆]SnF₆ and broadening of the resonance lines on cooling the crystals have been explained on the basis of host spin-lattice relaxation narrowing. The T₁ of Co²⁺ has been estimated to be ≈ 1.8 × 10⁻¹² s at 293 K.     

(H2O)6的稳定结构及异构过程研究

(H₂O)₆是形成三维立体结构的最小水分子团簇并具有能量较低的多个稳定异构体.本文利用从头计算方法研究了各稳定结构的异构化过程.(H₂O)₆的环状结构与最稳定结构的能量差0.31 eV为一个氢键的键能.水分子团簇的异构化是分子间氢键打开或重组的过程,不同异构体之间的转化每次只涉及一个氢键的打开或重组,异构化的能垒高度在0.07—0.21 eV之间. 关键词： 水分子团簇 2O)₆')" href="#">(H₂O)₆ 异构化过程 从头计算     

配合物[Zn(PSA)2(H2O)2]的合成及其晶体结构研究

合成了配合物单晶[Zn(PSA)2(H2O)2],其中PSA-为4-苯基丁酸根.配合物为单斜晶系,Cc空间群,a=3.8340(11)nm,b=0.51865(15)nm,c=1.0734(3)nm.a=90°,β=103.064(4).,r=90°,C20H26O6Zn.Mr=427.79,Z=4,V=2.0791(10)nm3,D=1.212g/cm3,F(000)=900,-46≤h≤43,-4≤k≤6,-13≤l≤13,R1=0.0780,wR2=0.2029.PSA-以两个氧原子与中心离子Zn(Ⅱ)离子形成四元螯合环,PSA与PSA反式构型.配合物分子之间存在氢键弱相互作用.     

Crystal Structure,Luminescence, and Triboluminescence of the Complex [Eu2(Quin)42H2O2Dipy]2(NO3)2H2O

Optics and Spectroscopy - An atomic structure of crystals of the complex [Eu2(Quin)42Н2O2Dipy]2 · 2(NO3) · Н2O, (Quin, anion of quinaldic acid; Dipy, 2,2'-dipyridyl),...     

[Fe3O（Ala）6（H2O）3]（ClO4）7和[Fe3O（Gly）6（H2O）3]（NO3）7·3H2O的顺原共振谱及变温磁化率研究

本文通过对[Fe 3O(Ala) 6(H 2O) 3](ClO 4) 7和[Fe 3O(Gly) 6(H 2O) 3](NO 3) 7·3H 2O的ESR谱的解析及变温磁化率的研究,得出它们的ESR谱具有各向同性的特点;朗德因子分别为2.019和1.997;两种配合物中铁离子间有反铁磁相互作用.     

Nonlinear response and optical limiting in SrBi(2)Ta(2)O(9) thin films

SrBi(2)Ta(2)O(9) (SBT) thin films on quartz substrates were prepared by use of the pulsed-laser deposition technique. The nonlinear refractive indices, n(2) , of the SBT films were measured by use of z-scan techniques with picosecond pulses. Large negative nonlinear refractive indices of 3.84 and 3.58cm(2)/GW were obtained for the wavelengths 532 nm and 1.064mum , respectively. The two-photon absorption coefficient was determined to be 7.3 cm/GW for 532 nm. The limiting behavior of SBT thin film on a quartz substrate was investigated in an f/5 defocusing geometry by use of 38-ps-duration, 532-nm, 1.064mum laser excitation.