共查询到20条相似文献,搜索用时 15 毫秒
1.
The X-ray photoemission spectra (XPS) of the A15 type compounds V3Au, Nb3Os, Nb3Ir, Nb3Pt and Nb3Au have been studied. The inner level binding energies of the different components and the valence electron distribution were measured. The Nb4d and the X5d energy bands of the Nb3X compounds appear to be more and more separate with increasing atomic number of the X component. The comparison between the results from X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) of corresponding V3X and Nb3X compounds points out the similarity of their electronic structures. 相似文献
2.
The thermoelectric power of linear chain synthetic metals Nb3X4 (with X=S, Se and Te) was measured from 5 to 300 K. The thermopower is negative indicating a dominant transport by electrons. Common to three compounds, in lower temperature regions the thermopower rises linearly with temperature but soon saturates. With respect to Nb3S4 and Nb3Se4 we have found no special anomaly of the thermopower except for a little higher magnitude.With respect to Nb3Te4 anomalies in the thermopower vs temperature appear at about 80 and 20 K which are explained in terms of the charge- density-wave phase transition from the simultaneous measurement of the resistivity and the observation of the electron diffraction patterns. 相似文献
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Upper critical field measurements of the A15 type compounds Nb~3Au,Nb3Au0.7Pt0.3 and Nb3Pt having Tc values of 10.7, 13.0 and 8.7K, respectively, show Hc2(0) values of 235, 295 and 125 kG, respectively. The data for the compounds containing Au fit closely calculations for a dirty type II superconductor with no paramagnetic limiting, but data for Nb3Pt are slightly above these calculations. 相似文献
4.
T. Jarlborg 《Solid State Communications》1978,28(7):529-531
Self-consistent LMTO (Linear Muffin Tin Orbital) band calculations have been performed for Nb3Si and V3In. Calculated pressures show agreement with the results from existing Nb3X and V3X compounds, when the lattice parameters are 5.125 and 5.025 Å (± 0.025 Å) respectively. At these lattice dimensions, the superconducting transition temperatures are predicted to be approximately 18 K for Nb3Si and 31 K for V3In. 相似文献
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K. Bohmhammel G. Wolf N.E. Alekseevskii E.P. Krasnoperov 《Solid State Communications》1977,21(6):519-520
Heat capacity of the Nb3Al0.8Ge0.2 samples have been measured in the temperature range 14–25K. It has been shown that the electron part of the heat capacity (γ) and the Debye temperature undergo only a small change after thermal treatment leading to significant increase of superconducting Tc. Such an increase of the band density of states N(EF)band may be caused by appropriate changes of phonon spectrum. The character of these changes is determined, to a great extent, by localization of the d-electrons in the niobium chains. 相似文献
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The Nb-chalcogenides Nb3X4 [1–3] with X = S, Se and Te, and Nb3S1.7Se2.3 were prepared from the elements using transport reactions with iodine at temperatures between about 730 and 1050°C. The ternary compound Nb3S1.7Se2.3 was confirmed to be isostructural with the hexagonal Nb3X4 of the space group . The Nb3X4-compounds were found to be superconductors, the transition temperatures to superconductivity reaching from 1.8 to 4.0 K. 相似文献
7.
The magnetic susceptibility and magnetization of the R5Pt3 intermetallic compounds have been studied. Gd5Pt3 is ferromagnetic while Tb5Pt3, Dy5Pt3 and Ho5Pt3 possess rather a non-linear magnetic structure, with strong ferromagnetic interaction and high anisotropy effects at low temperatures. 相似文献
8.
运用密度泛函理论计算了氧(O)在Nb3Ge表面的吸附,结果表明O倾向于吸附在Nb原子周围,并与Nb的电子轨道发生了明显的交叠,O与Nb形成兼具共价键和离子键特性的化学键。利用X射线光电子能谱对自然氧化的Nb3Ge表面进行成分分析发现:氧化层中只存在Nb的氧化物,理论计算结果与实验结果一致。由于O容易与Nb结合,最外层的Nb因逐渐氧化而耗尽,在接触势的驱使下,内部的Nb原子与最外层的Ge原子交换,最终使得Nb与O的形成氧化物在Nb3Ge表面聚集,在该氧化层下面是由于Nb的耗尽而形成的Ge聚集层。 相似文献
9.
运用密度泛函理论计算了氧(O)在Nb3Ge表面的吸附,结果表明O倾向于吸附在Nb原子周围,并与Nb的电子轨道发生了明显的交叠,O与Nb形成兼具共价键和离子键特性的化学键。利用X射线光电子能谱对自然氧化的Nb3Ge表面进行成分分析发现:氧化层中只存在Nb的氧化物,理论计算结果与实验结果一致。由于O容易与Nb结合,最外层的Nb因逐渐氧化而耗尽,在接触势的驱使下,内部的Nb原子与最外层的Ge原子交换,最终使得Nb与O的形成氧化物在Nb3Ge表面聚集,在该氧化层下面是由于Nb的耗尽而形成的Ge聚集层。 相似文献
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Madelung energy calculations are performed for two different lattices in which some of AB2X4 compounds (A = M+2, B = M?3, X = O?2, S?2, Se?2, Te?2) crystalline.A gross evaluation of the covalent bond energy contribution in the same crystals is made and some considerations are draw from the comparison between the two above quoted energy contributions. 相似文献
12.
《Physics letters. A》1972,40(5):415-416
Recent measurements of the shear mode spectrum in Nb3 Sn are interpreted in terms of the generalized Labbé- Friedel model. These measurements are shown to be consistent with the development of the pronounced Kohn anomaly at low temperatures. 相似文献
13.
The magnetic susceptibility of some rare earth-indium compounds has been measured in the temperature range 4.2–300 K under a constant field of 1 kOe. The compounds with R = Gd, Tb and Dy are antiferromagnetic, having Néel temperatures between 4.2 and 78 K ; those with R = Ho, Er and Tm seem to be ferromagnetic with ordering temperatures probably below 4.2 K. Y5In3 presents a temperature independent susceptibility. 相似文献
14.
The present paper is concerned with the X-ray spectrum study of binary niobium A15 compounds and of solid solution based on these compounds. In the case of Nb3Al the additional maximum of intensity in the long-wave length part of spectrum was observed. The results of the Al Kα-line shift and NbLβ2-lines study lead to the conclusion that the valence electron Al to Nb3Al, the decrease being still greater in the Nb3(Al-Sn) alloys. The valence electrons of tin are largely localized on the “parent” atom. 相似文献
15.
Self-consistent-field Xα cluster calculations are reported for MoS2, NbS2 and ZrS2. The results are compared with photoemission data. It is concluded that self-consistency and relaxation have a large effect on the relative position of the various energy levels in these compounds. 相似文献
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O. Demolliens F. Weiss R. Madar J.P. Sénateur J.C. Vallier 《Solid State Communications》1985,56(7):589-593
A laboratory process for long Nb3Ge tapes fabrication by chemical vapor deposition (CVD) has been set up. The Nb3Ge tapes which were fabricated offer the possibility of high current and high field operation at 4.2 K since the values of critical current densities, Jc, measured in high magnetic fields at 20T and 4.2K exceed 5 × 104 A cm?2 which is the generally accepted criterion for producing a superconducting magnet. 相似文献
18.
介绍了国内首个聚变堆用Nb3Sn超导磁体模型线圈。采用一维数学模型Gandalf对其管内电缆导体(CICC)结构的超导体稳定性进行仿真,得到了CICC稳定性裕度与磁场强度和运行电流之间的关系。这对于磁体的设计和运行都有十分重要的意义。 相似文献
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We have measured the resistivity of NbSe3 doped with 5% Ta from room temperature down to 0.5K and compared our results with similar measurements on pure NbSe3. The pure sample remains normal to the lowest temperature (0.5K), whereas the doped sample has a sharp transition to the superconducting state with Tc = 1.5 ± 0.2 K. Measurements of the critical magnetic field indicate that the Ta doped samples are homogeneous, anisotropic three dimensional superconductors. 相似文献