Synthesis and crystal structure of rare earth selenates Nd(HSeO4)3, Sm(HSeO4)3, and Nd2(SeO4)3 · 5H2O

Single crystals of rare earth (RE) selenates of the compositions Nd(HSeO₄)₃, Sm(HSeO₄)₃, and Nd₂(SeO₄)₃ · 5H₂O are synthesized and studied by X-ray diffraction analysis at T = 297 and 180 K. It is established that Nd and Sm hydrogen selenates are isostructural to one another and to the corresponding hydrogen sulfates. Neodymium selenate pentahydrate is not isostructural to the analogous RE sulfates, although their structural motifs are similar. __________ Translated from Kristallografiya, Vol. 49, No. 5, 2004, pp. 835–840. Original Russian Text Copyright ? 2004 by Zakharov, Troyanov, Kemnitz.     

Synthesis and crystal structure of oxonitrate complexes Cs[VO2(NO3)2], Cs[MoO2(NO3)3], and MoO2(NO3)2

Cs[VO₂(NO₃)₂] (I), MoO₂(NO₃)₂ (II), and Cs[MoO₂(NO₃)₃] (III) complexes have been obtained by crystallization from nitric solutions and studied by single-crystal X-ray diffraction. Complexes I and II contain infinite zigzag chains of similar compositions, [VO₂(NO₃)₂]⁻ and [MoO₂(NO₃)₂], in which V and Mo atoms form, respectively, trigonal- and pentagonal-bipyramidal polyhedra. Each of these polyhedrons also contains one terminal and two bridge O atoms and two terminal NO₃ groups which are monodentate and bidentate in complexes I and II, respectively. Complex III has an island structure and consists of Cs⁺ cations and [MoO₂(NO₃)₃]⁻ anions, in which the Mo atom is surrounded by one bidentate NO₃ group and two monodentate NO₃ groups and two terminal O atoms in the cis-positions; oxygen atoms form a polyhedron in the form of distorted octahedron. According to the ab initio calculation of isolated MoO₂(NO₃)₂ molecules in the gas phase and solution, the coordination environment of the Mo atom, similarly to the Cr(VI) atom in CrO₂(NO₃)₂, is formed by two bidentate nitrate groups and two terminal O atoms (polyhedron- twisted trigonal prism).     

一种新的非线性光学材料—Na3Sm2（BO3）3

本文采用固相反应法合成了一种新的硼酸盐化合物Na3Sm2(BO3)3,以Na2CO3-H3BO3为助熔剂,用悬挂铂丝法获得了3mm×2mm×0.5mm的透明单晶,X射线粉末衍射分析表明,该化合物属正交晶系,晶胞参数a=0.50585nm,b=1.10421nm,c=0.70316nm.红外光谱测量证实晶体结构中含有BO33-基团,粉末倍频效应测试表明该化合物具有非线性光学效应,粉末倍频信号强度接近KDP.     

Polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP)-based composite polymer electrolyte containing LiPF3(CF3CF2)3

This paper describes the preparation and characterization of lithium fluoroalkylphosphate-containing composite polymer electrolyte based on a polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) matrix. A mixture of ethylene carbonate and diethyl carbonate was used as a plasticizing agent and nanoscopic Al₂O₃ as a filler. The membranes were characterized by ac impedance, SEM, DSC, FTIR and fluorescence. An electrolyte with 2.5 wt% Al₂O₃ exhibited a conductivity of 9.8 × 10⁻⁴ S cm⁻¹ at ambient temperature. It was found that filler contents above 2.5 wt% rendered the membranes less conducting.     

Crystal and molecular structures of trifluoromethyl derivatives of fullerene C86, C86(CF3)16 and C86(CF3)18

Trifluoromethyl derivatives of C₈₆ were obtained by the reaction of a mixture of higher fullerenes with trifluoromethyl iodide, followed by the HPLC separation of the products. The crystal and molecular structures of C₈₆(CF₃)₁₆ (two isomers) and C₈₆(CF₃)₁₈ were determined by single-crystal X-ray diffraction using synchrotron radiation. All compounds studied are derivatives of the cage isomer of C₈₆ no. 17 (C ₂). Original Russian Text ? S.I. Troyanov, N.B. Tamm, 2009, published in Kristallografiya, 2009, Vol. 54, No. 4, pp. 637–641.     

Synthesis and crystal structure of (NH4)3[UO2(CH3COO)3]2[UO2(CH3COO)(NCS)2(H2O)]

Single crystals of the compound (NH₄)₃[UO₂(CH₃COO)₃]₂[UO₂(CH₃COO)(NCS)₂(H₂O)] (I) are synthesized, and their structure is investigated using X-ray diffraction. Compound I crystallizes in the monoclinic system with the unit cell parameters a = 18.3414(6) ?, b = 16.3858(7) ?, c = 12.4183(5) ?, β = 92.992(1)°, space group C2/c, Z = 4, V = 3727.1(3) ?³, and R = 0.0253. The uranium-containing structural units of crystals I are mononuclear complexes of two types with an island structure, i.e., the [UO₂(CH₃COO)₃]⁻ anionic complexes belonging to the crystal-chemical group (AB ₃⁰¹ = UO₂²⁺, B ⁰¹ = CH₃COO⁻) of the uranyl complexes and the [UO₂(CH₃COO)(NCS)₂(H₂O)]⁻ anionic complexes belonging to the crystal-chemical group AB ⁰¹M₃¹ (A = UO₂²⁺, B ⁰¹ = CH₃COO⁻, M ¹ = NCS⁻ or H₂O).     

Crystal structure of PbUO2(CH3COO)4(H2O)3

Single crystals of PbUO₂(CH₃COO)₄(H₂O)₃ have been investigated by X-ray diffraction (R = 0.029 for 3175 reflections). The structure of this compound is formed by [Pb(CH₃COO)(H₂O)₃]⁺ chains, which are oriented along the [100] axis and limited by one-core complexes [UO2(CH₃COO)₃]⁻. The coordination numbers of the Pb(II) and U(VI) atoms are 8, and the coordination polyhedron of uranium is a hexagonal bipyramid whose vertices contain oxygen atoms of three bidentate cyclic acetate groups and the uranyl group. Taking into account the different crystallographic roles of acetate ions, the crystal-chemical formula of [PbUO₂(CH₃COO)₄(H₂O)₃] chains can be written as AA′B ²¹ B ¹¹(B ⁰¹)₂ M ₃¹, where A = Pb; A′ = UO₂²⁺; M ¹ = H₂O; and B ²¹, B ¹¹, and B ⁰¹ are CH₃COO⁻ groups.     

YAl3(BO3)4: Crystal growth and characterization

The growth and characterization of YAl₃(BO₃)₄ (YAB), a potential nonlinear optical crystal for the fourth harmonic generation of Nd:YAG laser, was reported. Using top-seeded solution growth method, a YAB crystal with the dimensions of 16×16×18 mm³ was obtained from B₂O₃–Li₂O flux system. The advantages of this flux system and the growth process were discussed in detail. The as-grown YAB crystal was verified by powder X-ray diffraction. The transparency spectra indicated that the cut-off edge of the as-grown YAB was 170 nm. The fourth harmonic generation of a frequency doubled Nd:YAG laser, from 532 to 266 nm, was carried out with a YAB crystal doubler for the first time. Output pulse power obtained was 2.4 mW at 266 nm and the conversion efficiency from 532 to 266 nm was about 15.6%.     

Growth and properties of (Cr, Nd) doped GdCa4O(BO3)3 crystals

Optical quality Nd:GdCa₄O(BO₃)₃ (Nd:GdCOB) crystal and chromium sensitized crystal of Cr:Nd:GdCa₄O(BO₃)₃ (Cr:Nd:GdCOB) were grown by the Czochralski (CZ) method. The transmittance spectra was measured at room temperature on 7at%Nd:GdCOB and lat%Cr:7at%Nd:GdCOB samples. The absorption in the blue-UV region of Cr:Nd:GdCOB was larger than that of Nd:GdCOB, which matched the xenon flash lamp very well. A 3×3×10mm³ Nd:GdCOB sample without any antireflective coating was sidepumped using a pulsed dye-laser tuned to 595.4nm. The green-light output energy was 1.35mJ at a pump energy of 17.5mJ. The conversion efficiency was 7.7%, and the threshold energy was less than 1.2mJ which are the best results up to now to our knowledge. 3×3×7mm³ Nd:GdCOB and Cr:Nd:GdCOB samples without antireflective coatings were pumped using a flash pump source. The threshold for Cr:Nd:GdCOB was 0.9J while for Nd:GdCOB it was I.O.J. The output green light energy was 2.46mJ for Cr:Nd:GdCOB at a 10J flash pump energy and was 1.96mJ for Nd:GdCOB at the same pump energy, which clearly shows that Cr³⁺ ions have the sensitizing effect on the Nd³⁺ ions in Nd:GdCOB crystal.     

Crystallization behavior of (GeS2)0.1(Sb2S3)0.9 glass

The crystal growth kinetics of antimony trisulfide in (GeS₂)_0.1(Sb₂S₃)_0.9 glass has been studied by microscopy and DSC. The linear crystal growth kinetics has been confirmed in the temperature range 492 ? T ? 515 K (E_G = 405 ± 7 kJ mol⁻¹). The applicability of standard growth models has been assessed. From the crystal growth rate corrected for viscosity plotted as a function of undercooling it has been found that the most probable mechanism is interface controlled 2D nucleated growth. The non-isothermal DSC data, corresponding to the bulk sample, can be described by the Johnson-Mehl-Avrami equation.     

(La0.5Sr0.5)CoO3为电极的Pb(Zr0.4Ti0.6)O3和Pb(Zr0.2Ti0.8)O3铁电电容器结构及电学性能

分别采用磁控溅射法和溶胶-凝胶法(Sol-gel)制备了(La0.5Sr0.5)CoO3(LSCO)和Pb(Zr1-xTix)O3(PZT)薄膜,在Pt(111)/Ti/SiO2/Si基片上构架了LSCO/Pb(Zr0.4Ti0.6)O3(PZT(40/60))/LSCO和LSCO/Pb(Zr0.2Ti0.8)O3(PZT(20/80))/LSCO铁电电容器,研究了两种铁电电容器的结构和性能。XRD结构分析表明:两种四方相的不同Zr/Ti比例的PZT薄膜均为结晶良好的多晶钙钛矿结构。在5 V测试电压下,LSCO/PZT(40/60)/LSCO和LSCO/PZT(20/80)/LSCO两种铁电电容器的剩余极化强度(Pr)和矫顽场(Ec)分别为:28μC/cm2和1.2 V以及32μC/cm2和2 V。相对于PZT(40/60),PZT(20/80)具有较大的剩余极化强度和矫顽场,是由于其矩形度(c/a)较大。两种电容器都具有较好的脉宽依赖性和抗疲劳性。在5 V的测试电压下,LSCO/PZT(40/60)/LSCO电容器的漏电流密度为3.2×10-5A/cm2,LSCO/PZT(20/80)/LSCO电容器的漏电流密度为3.11×10-4A/cm2,经拟合分析发现:在0～5 V的范围内,两种电容器都满足欧姆导电机制。     

Structural study of (As2S3)0.6(GeS2)0.4 glass

(As₂S₃)_0.6(GeS₂)_0.4 glass in non-irradiated and γ-irradiated states has been studied by using high-energy synchrotron X-ray diffraction, extended X-ray absorption fine structure spectroscopy, and positron annihilation lifetime spectroscopy. The experimental results are explained by the local changes around As and Ge atoms upon irradiation. These changes are suggested to involve chemical bonds distortion, formation of defective bonds with wrong coordination, rotation of structural units and appearance of additional free volume in the glass network.     

Synthesis and X-ray diffraction study of (Cs0.5Ba0.25)[UO2(CH3COO)3] and Ba0.5[UO2(CH3COO)3]

Uranyl triacetate complexes (Cs_0.5Ba_0.25)[UO₂(CH₃COO)₃] (I) and Ba_0.5[UO₂(CH₃COO)₃] (II) are synthesized for the first time and their structures are determined by X-ray diffraction. Both compounds crystallize in the cubic crystal system. The crystal data are as follows: a = 17.3289(7) ?, V = 5203.7(4) ?³, space group I2₁3 and Z = 16 (I); a = 17.0515(8)?, V = 4957.8(4) ?³, space group I $ \bar 4 $ \bar 4 3d, and Z = 16 (II). In I and II, as in all uranyl triacetates studied earlier, the coordination polyhedron of the uranium atom is a hexagonal bipyramid whose vertices are occupied by the oxygen atoms of the uranyl and three acetate groups. The uranium-containing group belongs to the AB ₃⁰¹ (A = UO₂²⁺, B ⁰¹ = CH₃COO⁻) crystal chemical group of uranyl complexes. It was found that compound II is isostructural to the (Rb_0.50Ba_0.25)[UO₂(CH₃COO)₃] studied earlier.     

Crystal growth of NdAl3(BO3)4 from K2O/MoO3/Nd2O3/B2O3/KF flux

NdAl₃(BO₃)₄ single crystals were grown by the flux method and the TSSG technique using a K₂O/3MoO₃/B₂O₃/0.5Nd₂O₃/KF flux system. Light-violet clear crystals could be obtained. The effects of fluoride on the growth of NAB crystals were investigated. As the content of KF was gradually increased, the growth form of NAB was changed from the equant to the columnar and the primary crystalline region of NAB was shrinked. At the ratio of KF/K₂O = 0.75, NAB crystals could not be grown.     

Sodium tracer diffusion in glasses of the type (Na2O)0.2(B2O3)y(SiO2)0.8 − y

Sodium tracer diffusion coefficients, D^?_Na, have been measured in sodium borosilicate glasses of the type (Na₂O)_0.2(B₂O₃)_y(SiO₂)_0.8−y as a function of temperature and the composition parameter y. At constant temperature, the tracer diffusion coefficient of sodium decreases as y increases. The activation enthalpy derived from sodium tracer diffusion data for temperatures up to about 350 °C increases about linearly with increasing values of y from about 70 to 100 kJ/mol. The pre-exponential factor of the sodium tracer diffusion coefficient as a function of y varies by about one order of magnitude and has a minimum at near y = 0.3.     

Viscosity of (GeSe2)x(Sb2Se3)1−x undercooled melts

Viscosity of (GeSe₂)_x(Sb₂Se₃)_1−x undercooled melts (x = 0.4-0.8) was measured using parallel-plate method and penetration method. By using these two techniques viscosity of the whole measurable region of undercooled melt and of the part of glass region can be measured. In this relatively broad viscosity interval (seven orders of magnitude) all measured samples show Newtonian behavior and the dependence of their viscosity on temperature can be described by a simple Arrhenius equation. The kinetic fragilities calculated from these dependencies show similar compositional dependence as heat capacity changes at glass transition measured by DSC.     

Crystal structure of britvinite [Pb7(OH)3F(BO3)2(CO3)][Mg4.5(OH)3(Si5O14)]: A new layered silicate with an original type of silicon-oxygen networks

The crystal structure of a new mineral britvinite Pb_7.1Mg_4.5(Si_4.8Al_0.2O₁₄)(BO₃)(CO₃)[(BO₃)_0.7(SiO₄)_0.3](OH, F)_6.7 from the Lángban iron-manganese skarn deposit (V?rmland, Sweden) is determined at T = 173 K using X-ray diffraction (Stoe IPDS diffractometer, λMoKα, graphite monochromator, 2θ_max = 58.43°, R = 0.052 for 6262 reflections). The main crystal data are as follows: a = 9.3409(8) ?, b = 9.3579(7) ?, c = 18.8333(14) ?, α = 80.365(6)°, β = 75.816(6)°, γ = 59.870(5)°, V = 1378.7(2) ?³, space group P1, Z = 2, and ρ_calcd = 5.42 g/cm³. The idealized structural formula of the mineral is represented as [Pb₇(OH)₃F(BO₃)₂(CO₃)][Mg_4.5(OH)₃(Si₅O₁₄)]. It is demonstrated that the mineral britvinite is a new representative of the group of mica-like layered silicates with structures in which three-layer (2: 1) “sandwiches” composed of tetrahedra and octahedra alternate with blocks of other compositions, such as oxide, oxide-carbonate, oxide-carbonate-sulfate, and other blocks. The tetrahedral networks (Si₅O₁₄)_∞∞ consisting of twelve-membered rings are fragments of the britvinite structure. Similar networks also form crystal structures of the mineral zeophyllite and the synthetic phase Rb₆Si₁₀O₂₃. In the crystal structures under consideration, the tetrahedral networks differ in the rotation of tetrahedra with respect to the layer plane. Original Russian Text ? O.V. Yakubovich, W. Massa, N.V. Chukanov, 2008, published in Kristallografiya, 2008, Vol. 53, No. 2, pp. 233–242.