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排序方式: 共有174条查询结果,搜索用时 15 毫秒
81.
S. Majumdar R.K. Singha K. Das M. Chakraborty A.K. Das S.K. Ray 《Physica B: Condensed Matter》2008,403(12):2059-2064
Ribbon samples of Cu0.95Co0.05 were prepared by melt spinning method to perform systematic investigations on structure and transport properties as a function of annealing temperature. X-ray diffraction study shows that the ribbon is polycrystalline with a strong 2 0 0 texture along the surface normal of the as-quenched Cu0.95Co0.05 ribbon and the degree of texture is enhanced upon annealing. The compressive stress, which relaxes upon annealing, is observed in as-quenched ribbon. The resistivity, which is higher in as-quenched ribbon, decreases toward the bulk value of Cu upon annealing. The compressive stress and higher resistivity in as-quenched ribbon are attributed to the incorporation of Co atoms/particles in Cu matrix. The decrement of the stress and resistivity upon annealing is due to the precipitation of Co atoms from the Cu matrix, segregating as Co or Co-rich Cu grains as observed from the transmission electron microscopy measurements. 相似文献
82.
本文采用在金刚石表面蒸镀铝电极的方法测量金刚石膜的电阻率。样品的Raman,SEM,XRD分析结果表明,金刚石膜的电阻率与晶粒尺寸、晶粒取向和缺陷及杂质有直接关系,大尺度晶粒的金刚石膜具有较高的电阻率,高比例的I(110)/I(111)晶粒取向的金刚石膜具有较高的电阻率;结构缺陷和杂质含量较小的金刚石膜具有较高的电阻率。 相似文献
83.
The electrical conductivity of a liquid dielectric is one of its most important properties; however, it is typically measured in the low-voltage range whereas the features of the current passage processes under the effect of strong electric field remain poorly investigated. The paper presents an experimental technique for rapid measurement of the high-voltage conductivity. The current–voltage characteristics obtained with the voltage modulation by a saw-tooth signal underlie the proposed technique. Some examples are given to demonstrate the importance of its application. The experimental data were complemented with the computer simulation of the corresponding processes. 相似文献
84.
Klaus Stöwe 《Journal of solid state chemistry》2003,176(2):594-608
We report about the LMTO-ASA band structure, ELF and COHP calculations for a number of alkali metal rare earth tellurides of the formulas ALnTe4 (A=K, Rb, Cs and Ln=Pr, Nd, Gd) and KLn3Te8 (Ln=Pr, Nd) to point out structure-properties relations. The ALnTe4 compounds crystallize in the KCeSe4 structure type with Te ions arranged in the form of 4.32.4.3 nets, in which interatomic homonuclear distances indicate an arrangement of isolated dumbbells. This could be verified by the COHP and ELF calculations, both of which revealed isolated [Te2] units. But in contrast to the ionic formulation as A+Ln3+ ([Te2]2−)2, which can be deduced from this observation, the band structure calculations for KPrTe4, KNdTe4, RbNdTe4 and CsNdTe4 reveal metallic conductivity. This behavior was verified for KNdTe4 by resistivity measurements performed by a standard four-probe technique. We explain these results by an incomplete carryover of electrons from the rare earth cation onto tellurium due to covalent bonding leaving parts of the Te-Te ppπ* antibonding states unoccupied. On the other hand the calculations suggest insulating behavior for KGdTe4 resulting from a complete filling of the Te-Te ppπ* antibonding states due to the increased stability of the half filled 4f shell. The ALn3Te8 compounds crystallize in the KNd3Te8 structure type, a distorted addition-defect variant of the NdTe3 type with 44 Te nets. As polyanionic fragments L-shaped [Te3]2− and infinite zig-zag chains ∞1[Te4]4− are observed (with interatomic homonuclear distances in the range 2.82-3.00 Å), which are separated from each other by distances in the range 3.27-3.49 Å. Again COHP calculations made evident that these latter interactions are secondary. Within the infinite zig-zag chains ∞1[Te4]4− the Te ions at the corners of the chain have a higher negative charge than the linear coordinated ones in the middle. KPr3Te8 and KNd3Te8 are semiconductors, verified for the latter by resistivity measurements. 相似文献
85.
The crystal structures of three new intermetallic ternary compounds in the LnNiSb3 (Ln=Pr, Nd and Sm) family have been characterized by single crystal X-ray diffraction. PrNiSb3, NdNiSb3 and SmNiSb3 all crystallize in an orthorhombic space group, Pbcm (No. 57), Z=12, with , , , and ; , , , and ; and , , , and , for Ln=Pr, Nd and Sm, respectively. These compounds consist of rare-earth atoms located above and below layers of nearly square, buckled Sb nets, along with layers of highly distorted edge- and face-sharing NiSb6 octahedra. Resistivity data indicate metallic behavior for all three compounds. Magnetization measurements show antiferromagnetic behavior with (PrNiSb3), 4.6 K (NdNiSb3), and 2.9 K (SmNiSb3). Effective moments of 3.62 μB, 3.90 μB and 0.80 μB are found for PrNiSb3, NdNiSb3 and SmNiSb3, respectively, and are consistent with Pr3+ (f 2), Nd3+ (f 3), and Sm3+ (f 4). 相似文献
86.
87.
Philippe Gall 《Journal of solid state chemistry》2008,181(1):1-6
Polycrystalline samples and single crystals of the R4Mo4O11 compounds (R=Yb and Lu) were synthesized by solid-state reactions at high temperature in sealed Mo crucibles. The structure of Lu4Mo4O11 (a=10.5611(1), b=5.61930(5), c=15.6877 (2), β=99.5131(4) and Z=4) was determined by single crystal X-ray diffraction and refined by least squares on F2 converging to R1=0.0425, wR2=0.0980 for 3508 intensities. Contrary to the R4Mo4O11 compounds with lighter rare earths, which crystallize in the orthorhombic space group Pbam, the Yb and Lu compounds crystallize in the monoclinic space group P2/m. The R4Mo4O11 compounds contain distorted infinite oxide-molybdenum chains of trans-edge-sharing Mo6 octahedra diluted with the rare earths. Magnetic susceptibility measurements indicate that the oxidation state of the Yb atoms is +3, affording 14 metallic valence electrons per Mo4 fragment and, the absence of localized moments on the Mo network. Resistivity measurements on single crystals show that the Yb4Mo4O11 and Lu4Mo4O11 compounds are small band-gap semi-conductors. 相似文献
88.
A simple multi-contact measurement method, which can be used to map the electrical resistivity of small disc-shaped samples of conducting polymer during temperature ageing, was examined for its resolution and accuracy. The method is based on electrical impedance tomography (EIT), which is used especially in medicine to visualise boundaries between areas having different electrical resistivities. In order to eliminate experimental errors, a computer simulation was used for testing. The time series of resistivity maps were recorded during ageing of real polymer samples. The contour maps and their time development are presented graphically and discussed. 相似文献
89.
In the paper, mathematical models for determination of resistivity of thin antistatic coatings are presented. The models use the four-points method and the method of images. The relations between the sample size and the distance between the electrode set and the edge of the sample were analyzed. It was found that the distance between the electrode set and the object edge should be at least 5 times greater than the electrode spacing to allow us using much simpler formulas for infinite flat object with measurement uncertainty below 5%. The correctness of theoretical considerations was verified experimentally. 相似文献
90.
D.L. Gao 《Applied Surface Science》2009,255(7):4185-4191
Electroless copper plating on micron-scale acrylate rubber (ACM) microspheres was studied. The core-shell structured Cu-coated ACM microspheres with high conductivity and low density were fabricated by introducing a reaction control method. Via multi-times activating treatment, the acrylate rubber (ACM) microspheres were implanted with more Ag catalytic active centers on the surfaces to promote the formation of coatings. The surface-coating structures and the electrical properties of Cu-coated ACM microspheres were investigated. It was found that the Cu-coated ACM microspheres were a kind of elastic particles. The different coating structures could be produced by controlling the extent of plating reaction. The coated microspheres with different coating structures were conductive, and their volume resistivities decreased remarkably with the increasing of applied pressure and varied with the temperature according to their surface coating structures. 相似文献