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1.
Antonio F. Fuentes M. Garza-Garc?&#x;a G. Mendoza-Suárez U. Amador 《Journal of solid state chemistry》2003,175(2):299-305
We describe in this work the synthesis and crystal structure of five rare earth and Mo(VI) or W(VI) containing complex perovskites. The compounds studied are Ba(Dy2/3Mo1/3)O3, Ba(Dy2/3W1/3)O3, Ba(Gd2/3Mo1/3)O3, Ba(Gd2/3W1/3)O3 and Ba(Sm2/3W1/3)O3 and were prepared starting from solutions, by the polymeric precursors method. Structural characterization by HREM, SAED and powder XRD revealed the five compounds to be ordered cubic perovskites, SG Fm-3m (225), with a cell parameter double of that of a simple perovskite cell and increasing as the size of the trivalent lanthanide ion increases (Dy<Gd<Sm). 相似文献
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Four hexagonal molybdenum nitrides—three modifications of δ-MoN and Mo5N6—were prepared by the plasma-enhanced chemical vapour deposition (PECVD) method and ammonolysis of MoCl5 and MoS2. The nitrides were structurally characterised by X-ray diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. δ1-MoN is best described by the WC-type structure with stacking faults due to nitrogen atom disorder. Ordering of nitrogen atoms results in δ2-MoN with the NiAs-type structure. Formation of trigonal molybdenum clusters in δ3-MoN is responsible for the doubling of the unit cell in a and b directions compared to δ2-MoN. Mo5N6 can be viewed as an intergrowth structure of the WC- and NiAs-type building blocks, accompanied by vacancies on Mo sites. Influence of reaction conditions on the formation of the four nitrides is discussed; their magnetic properties are presented. 相似文献
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以BaCO_3,MnCO_3和Yb_2O_3为原料,采用传统固相烧结法,在1300 ℃下合成了两种新的化合物12R-Ba_4YbMn_3O_(11.5)和10H-Ba_5YbMn_4O_(14.5).用X射线能谱(EDS)微区成分分析和氧化还原滴定法确定两种化合物的化学式,用选区电子衍射(SAED)以及粉末X射线衍射Rietveld结构精修等手段分析测定了对化合物的晶体结构.12R-Ba_4YbMn_3O_(11.5)的空间群为R-3m,晶胞参数为a=0.578 nm,c=2.850 nm;10H-Ba5 YbMn_4O_(14.5)的空间群为P63/mmc,晶胞参数为a=0.575 nm,C=2.377 nm. 相似文献
4.
High-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS) and selected area electron diffraction (SAED) were used to study gadolinium and lanthanum silicate films deposited on Si(1 0 0) substrates using electron-beam evaporation from pressed-powder targets. As-deposited films consist of an amorphous silicate layer without an interfacial layer. After annealing at 900 °C in oxygen for 2 min, an interfacial SiO2 layer is formed in the gadolinium silicate film, while this interfacial layer is a SiO2-rich lanthanum silicate layer in the lanthanum silicate film. The formation of interfacial silicate layers is thermodynamically more favorable for the lanthanum films than for the gadolinium films. The gadolinium silicate films crystallize at a temperature between 1000 and 1050 °C, while the crystallization temperature for the lanthanum silicate films is between 900 and 950 °C. 相似文献
5.
T.‐C. Rdel D. Wang D. S. Su M. Lerch A. Prokofiev K. D. Luther W. Assmus 《Crystal Research and Technology》2006,41(10):950-954
The aim of this work is the preparation of nitrogen‐doped single crystals of cation‐stabilized zirconia. Thin plates of these crystals were nitrided in a graphite heated resistance furnace with nitrogen as reaction gas. Several dwell times and reaction temperatures were tested and their effect on the amount of incorporated nitrogen is investigated. During nitridation at high temperatures a rock salt‐type ‘ZrN’ layer grows on the surface, leading to the destruction of the crystal. In contrast to the fluorite‐type bulk material, which can be described as a fast anion conductor, the surface layer shows electronic conductivity. For possible applications of the bulk material (solid electrolyte) the formation of the surface layer must be avoided. Therefore, the interface between surface epilayer and bulk material was investigated in detail by electron microscopy methods. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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7.
Adjustable microwave absorption properties of flake shaped (Ni0.5Zn0.5)Fe2O4/Co nanocomposites with stress induced orientation 总被引:1,自引:0,他引:1
Flake shaped (Ni0.5Zn0.5)Fe2O4/Co nanocomposites were successfully fabricated by co-precipitating of Ni-Zn ferrite on the surface of cobalt nanoflakes. The electromagnetic characteristics of the samples were studied at the frequency of 0.1–14 GHz. The results showed that the cobalt nanoflakes in compacted nanocomposites were well orientated, and the nanocomposites were characterized with low optimal reflection loss (RL) of −33.8 dB at 11.5 GHz and broad RL bandwidth for <−20 dB in the frequency range of 7.6–12.1 GHz. At the same time, the position of the absorptive band can be adjusted by changing the mass ratio of ferrite to cobalt in the nanocomposites. It is proposed that the excellent microwave absorption properties are related to the combination of strong shape anisotropy of cobalt nanoflakes and adjustable dielectric loss. 相似文献
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Novel rare-earth-containing manganites, Ba4REMn3O12 (RE=Ce, Pr), with 12R structure, have been prepared by solid-state reaction. Although the phases are formed at 950°C, to obtain single-phase samples high temperatures (up to 1300°C) and long synthesis periods are needed.Their structure is built up from chains of BO6 face-sharing and corner-sharing octahedra running along the c-axis giving a quasi-one-dimensional oxide. Every polyhedral column consists of (Mn3O12) units of three face-sharing octahedra, both ends connected by the three terminal oxygen atoms to three different (REO6) octahedra. Mixed occupation of the three octahedral positions in the structure, (Mn(1), Mn(2) and Re), was not found. Vacancies are not observed, neither in the cationic sublattice nor in the oxygen one. Thus, as in all the other 1-D manganites, the oxidation state of manganese ions seems to be four, as the rare-earth valence is. High-resolution electron microscopy suggests the eventual existence of ordered polytypes for different compositions, which could be stabilized by adjusting the thermodynamic conditions. 相似文献
10.
Electroless deposited Ni-P and Co-P coatings, modified by introducing additional elements such as Zn and W are presented.
The characteristics alterations of the multicomponent films are reviewed in connection with the particularities of co-deposition
of the third metal. Based on the fair correspondence between TEM, microdiffraction and precise XRD analysis it is shown that
the structure type and lattice parameters of polycrystalline Ni-Me-P and Co-Me-P films are practically identical to pure Ni
and Co metals. No impurity phase is detected by XRD. The location of the third element is determined using TEM with EDS. The
conclusion is drawn about the grain boundary segregation of Zn and W along with P. Earlier studies by XPS and AES showed that
Zn is partially oxidized, whereas W is in elemental form inside the coatings. Crystallites built of lamellas with thickness
within the nanometer scale are observed in Ni-W-P and Co-W-P by TEM.
Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 6, pp. 764–770.
The text was submitted by the authors in English. 相似文献