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71.
为了确定ZrO2和(ZrO2)0.97(Bi2O3)0.03的晶体结构和原子热振动各向同性温度因子B,对该粉末晶体进行X射线衍射实验,建立了晶体结构模型,进行晶体结构分析。首先,采用共沉淀法和高温固相烧结法制备了纳米氧化锆ZrO2和(ZrO2)0.97(Bi2O3)0.03粉末晶体,接着,使用X射线测试仪对两种样品进行了衍射实验(XRD),利用Rietveld 精修方法的 RIETAN-2000程序对所得实验结果进行了晶体结构分析,获得了晶体结构参量和原子热振动各向同性温度因子B。通过Maximum Entropy Method(MEM)解析得到了粉末晶体(ZrO2)x(Bi2O3)1-x(x=1.0,0.97)的等高电子密度分布可视化图谱。结果表明,(ZrO2)0.97(Bi2O3)0.03的晶胞体积比ZrO2的晶胞体积大分别为140.6850 Å3和140.5637Å3;ZrO2晶体的原子热振动各向同性温度因子B(Zr)、BO(1)、BO(2)和 B(Bi)分别为0.690、0.269、 0.178 和 0 Å2,(ZrO2)0.97(Bi2O3)0.03晶体的分别为0.460 、0.583 、0.121 和0.581 Å2。 确定了(ZrO2)0.97(Bi2O3)0.03的晶体结构属于单斜晶系,实现了等高电子密度分布三维(3D)和二维(2D)的可视化,进一步确定了晶体结构和原子位置。 相似文献
72.
Dispersed nickel oxide nanoparticles were obtained by a simple and low-cost method using a mixture of gelatin as organic precursor
and NiCl2 · 6H2O as Ni source. The average particle size was estimated from X-ray powder diffraction (XRPD) peaks using the Rietveld refinement.
The values ranged from 3.2 to 79 nm. We observed that the particle size changes as a function of synthesis time, with a notable
decrease after the addition of NaOH to the solution. Field emission scanning electron microscopy (FE-SEM) measurements show
that particles have well defined shapes and are dispersed in an organic matrix. X-ray absorption near edge spectroscopy (XANES)
shows also the formation of fcc NiO nanoparticles structures. 相似文献
73.
Mullite-type Bi2(Ga1-xFex)4O9 solid solutions, with 0.1 ≤ x ≤ 0.9, have been synthesized by a combination of mechanical and thermal treatments of a Bi2O3/Ga2O3/α-Fe2O3 stoichiometric mixture. The microstructure of the as-prepared materials on the long-range and local atomic scales was investigated by X-ray diffraction and 57Fe Mössbauer spectroscopy, respectively. The XRD data analysis revealed in all cases linear dependence of the lattice parameters related on x. Due to the ability of the applied Mössbauer spectroscopy to probe the local environment of Fe cations, the local structural disorder in investigated solid solutions is provided. It was shown that the presence of Fe3+ cations in octahedral sites of the orthorhombic structure causes a local distortion of polyhedra in the material. The preferential occupation of Fe in octahedral site was revealed. Detailed quantitative information on both the cation distribution and the bond lengths provided is discussed in relation to the derived hyperfine parameters. 相似文献
74.
G. Garg S.E. Lofland M. Greenblatt K. Vijayamohanan 《Journal of solid state chemistry》2003,174(1):229-232
A monophasic sample of Ag2MnSn3S8 has been prepared by heating stoichiometric amounts of the constituent metals and sulfur in evacuated silica tubes at 670°C. Structural analysis of Ag2MnSn3S8 using Rietveld refinement of powder X-ray diffraction data shows that it crystallizes in the space group with a=10.6984(2) Å. Magnetization measurements in the temperature range 5-300 K indicate paramagnetic behavior with a μeff of 5.80 μB, consistent with the divalent nature of manganese. Electrochemical studies show a coulombic capacity of ∼50 Ah kg−1 for the cell constructed with Ag2MnSn3S8 as the positive electrode. 相似文献
75.
S. Aoyagi Y. Kuroiwa A. Sawada H. Kawaji T. Atake 《Journal of Thermal Analysis and Calorimetry》2005,81(3):627-630
Summary The size effect on the crystal structure including the chemical bonding nature has been investigated for several kinds of BaTiO3 nanopowder with the particle sizes down to 50 nm in diameter, by means of powder diffraction using high-energy synchrotron radiation. The Rietveld refinement reveals that the BaTiO3 nanopowder consists of tetragonal and cubic structure components at 300 K. The feature of coexistence can be illustrated by the core/shell model for the particle, in which the shell with a cubic structure covers the core with a tetragonal structure. The thickness of the cubic shell is almost constant irrespective of the particle sizes, and is estimated as approximately 8 nm. Hence, the critical particle-size, where the entire particle is covered with the cubic shell, is suggested as 16 nm. The charge density distributions of the BaTiO3 nanopowder in the cubic phase at 410 K are revealed by the maximum entropy method. Changes in the bonding electron density and the ionic valence expected are not observed clearly even in the 50 nm crystal compared with the bulk crystal. 相似文献
76.
Masatomo Yashima Atsushi Sakai Akinori Hoshikawa 《Journal of solid state chemistry》2003,175(2):272-277
The crystal structure of sintered β-tricalcium phosphate, Ca3(PO4)2, was refined using a high-resolution neutron powder diffraction data and the Rietveld method. This material was confirmed to have a rhombohedral structure (space group R3c, Z=21). Unit-cell parameters with higher precision (a=b=10.4352(2) Å, c=37.4029(5) Å, α=β=90°, and γ=120° in the hexagonal setting) and positional parameters for oxygen with equal precision were obtained by the neutron powder diffraction technique, compared with the single-crystal X-ray diffraction data by Dickens et al. (J. Solid State Chem. 10 (1974) 232). The site Ca(4) with atomic coordinates [0.0, 0.0, −0.0851(6)] was confirmed to be very different from the other four Ca sites: The position Ca(4) is three-fold coordinated with oxygen atoms, and has lower occupancy factor of 0.43(4), and a higher isotropic thermal parameter. On the contrary, each of the Ca(1), Ca(2), Ca(3), and Ca(5) is fully occupied by one Ca atom and these positions are coordinated with seven, eight, eight, and six oxygen atoms, respectively. The bond valence sums of Ca(4) and Ca(5) are lower (0.7) and higher (2.7), respectively, than the others (1.8-2.1). 相似文献
77.
Ángeles G. De la Torre Antonio J. M. Cuberos Gema Álvarez‐Pinazo Ana Cuesta Miguel A. G. Aranda 《Journal of synchrotron radiation》2011,18(3):506-514
Belite sulfoaluminate (BSA) cements have been proposed as environmentally friendly building materials, as their production may release up to 35% less CO2 into the atmosphere when compared with ordinary Portland cement fabrication. However, their formation mechanism has not been studied in detail so far. Here, an in situ high‐temperature high‐resolution synchrotron X‐ray powder diffraction study is reported. Two types of BSA clinkers have been characterized, both containing 50–60 wt% C2S and 20–30 wt% C4A3 as main phases. One type is iron‐rich and a second type (with different phase assemblage) is aluminium‐rich. Furthermore, the C2S phase reacts slowly with water, thus activation of this compound is desirable in order to enhance the mechanical strength development of the resulting cements. To do so, iron‐rich BSA clinkers have been doped with minor amounts of B2O3 and Na2O to promote stabilization of α‐forms of C2S, which are more reactive with water. The decarbonated raw materials were loaded into Pt tubes and heated to between 973 K and 1673 K, and patterns were collected using a high‐energy synchrotron beam of wavelength λ = 0.30 Å. The thermal stability of Klein's salt in these clinkers has been clarified. Several reactions have been followed: formation and decomposition of Klein's salt, melting of aluminates and ferrite, and polymorphic transformations of dicalcium silicate: ‐C2S →α‐C2S. Changes in mineralogical phase assemblages at a given temperature owing to the addition of minor amounts of selected elements have also been determined. 相似文献
78.
S. V. Kolotilov A. V. Shvets V. N. Solomakha 《Theoretical and Experimental Chemistry》2006,42(1):43-47
Increasing length of the bipyridyl bridging ligands in a series of similar complexes facilitates the formation of microporous
coordination polymers. The structure of one of these compounds was found by the Rietveld method. These compounds were found
to differ in their adsorption caparcities relative to methanol, nitrogen, and hydrogen.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 39–43, January–February, 2006. 相似文献
79.
S. N. Achary O. D. Jayakumar S. J. Patwe A. B. Shinde P. S. R. Krishna S. K. Kulshreshtha A. K. Tyagi 《Pramana》2008,71(5):941-946
Herein we report the results of detailed crystallographic studies of Ca1−x
Ba
x
Zr4P6O24 compositions from combined Rietveld refinements of powder X-ray and neutron diffraction data. All the studied compositions
crystallize in rhombohedral lattice (space group R-3 No. 148). A continuous solid solution is concluded from the systematic
variation of unit cell parameters. The variation of unit cell parameters with the composition indicates decreasing trend in
a parameter with increasing Ba2+ concentration contrast to an increasing trend in c parameter.
相似文献
80.
HUANG Qing-Ming~① 《结构化学》2010,29(7):993-1000
<正>Upconversion(UC)phosphor Tm~(3+)doped YF_3 nano-crystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy(TEM),Scanning electron microscopy(SEM)and X-ray diffraction(XRD).Their UC luminescence properties were studied by fluorescence spectrophotometer with 980 nm diode laser excitation,and impact of different grain sizes and morphology on the UC luminescence intensity was discussed.The fluorescence decay lifetime was calculated by Multi-exponential function fitting method.Results show that UC emission intensity was enhanced with the reduction of grain size,and the decay lifetime is 0.60 us. 相似文献