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《Physica C: Superconductivity and its Applications》2002,360(1-2):55-58
Reactivity of several oxide materials (OM) with BSCCO powder and oxygen diffusion through OM layer has been tested at temperature ≈840 °C in air. The OM (e.g.: BaZrO3, SrCO3, MgO and ZrO2) showing the low or no reactivity with BSCCO have been mixed (10 wt.%) with precursor powder and used for single-core tapes. Bi-2223/Ag/OM/Ag single-core tapes with oxide barriers made of BaZrO3, SrCO3, ZrO2 and Al2O3 have been also prepared by a standard powder-in-tube technique. The used OM in the direct contact with BSCCO influences the electrical properties of Bi-2223 phase differently. These is because the oxides react with BSCCO during the heat treatment and simultaneously affect the 2212→2223 phase transformation, the Bi-2223 grain growth and so also grain connectivity. SrCO3 powder has been evaluated as the best material from the point of no destructive effect on 2223 phase transport current property. The oxide barrier controls the oxygen diffusion during the tape heat treatment and simultaneously the HTS phase formation kinetics, its purity and content within the superconducting core. For single-core Bi-2223/Ag/OM/Ag tapes, the highest current density was measured for Al2O3 due to only slightly reduced oxygen diffusion through the barrier. 相似文献
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High quality BSCCO thin films have been fabricated by means of an ion beam sputtering at various substrate temperatures, Tsub, and ozone gas pressures, pO3. The correlation diagrams of the BSCCO phases appearing against Tsub and pO3 have been established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 phases as well as Bi2212 have emerged as stable phases depending on Tsub and pO3. From these results, the thermodynamic evaluations of ΔH and ΔS, which are related with Gibbs’ free energy change for single Bi2212 or Bi2223 phase have been performed. 相似文献
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Wei Guo 《Physica C: Superconductivity and its Applications》2010,470(9-10):440-443
61-Filaments Bi-2223/Ag superconducting tapes have been successfully joined with BSCCO superconducting powder interlayer by diffusion bonding. The electrical properties of the diffusion bonding joints were tested by standard four probe method and the microstructures of the joints were also examined by SEM. Additionally, the phase constituents of the superconducting powders between the tapes before and after bonding process were evaluated by XRD analysis. The result shows that the diffusion bonding joints are superconductive. The microstructures of the joint display a good bonding with no cracks and discontinuities. The joining zones are mainly composed of Bi-2223 phase, Bi-2212 phase and a small amount of CuO, Ca2PbO4. At last, the phase transformations of the superconducting powders in the bonding process are discussed. 相似文献
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J.Y. Li L. Soubeyroux H.L. Zheng C.S. Li Y.F. Lu L. Porcar R. Tournier L. Zhou 《Physica C: Superconductivity and its Applications》2006,450(1-2):56-60
The phase evolution during melting and recrystallization of (Bi,Pb)2Sr2Ca2Cu3O10 ((Bi,Pb)-2223) core in a Ag-sheathed monofilamentary tape has been investigated. The tape was fabricated by PIT process with powders containing nearly pure (Bi,Pb)-2223 phase. Short samples were melted at 805 °C, 808 °C, 812 °C, 816 °C, 831 °C, slowly cooled at 1.5 °C/h under flowing 1.6% O2 balanced with argon and quenched in air at room temperature. X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) were applied for the phase identification. The results show that (Bi,Pb)-2223 core is partially melted into a liquid and alkaline earth cuprates (AECs), mainly 2:1-AEC, at 805 °C, 808 °C, 812 °C, and well reforms directly from the melt during the slow cooling. More (Bi,Pb)-2223 phase is decomposed at temperatures higher than 816 °C, but cannot recrystallize, indicating that a partial melting at some temperatures around a given temperature range is essential to (Bi,Pb)-2223 phase reformation. The melt composition moves from that between “2223” and “2212” stoichiometries towards 2212-like stoichiometry with increasing temperature. This seems to lead to the conclusion that (Bi,Pb)-2223 phase decomposes incongruently into a 2212-like liquid and (Ca,Sr)-cuprates. 2:1-AEC plays the most important role in (Bi,Pb)-2223 melt-recrystallization process. Our results also reveal that plate-like shape (Bi,Pb)-2223 grains can be obtained via melting and recrystallization if the optimum processing conditions are used. 相似文献
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After annealing of Bi,Pb-2223/Ag composites in a nitrogen-oxygen atmosphere with a low oxygen content in the 2223 phase, cross-polarized
waves of oxygen atomic displacements have been revealed by electron diffraction in the [010]2223 direction. It has been demonstrated using the methods of X-ray photo-electron spectroscopy and nuclear microanalysis that
nitrogen does not interact with the 2223 lattice and that the oxygen index (9.67 ± 0.20) becomes less than the stoichiometric
index (x = 10). It has been found that the generation of atomic displacement waves is due to the deficiency of oxygen in the double
Bi-O layers. 相似文献
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Il Nuovo Cimento D - BSCCO (2223) phase superconductor, prepared by the traditional solid-state reaction route, was densified by hot pressing, yielding high-density and textured-bulk materials. A... 相似文献
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用于限流器的Bi-2212超导筒的研制 总被引:2,自引:0,他引:2
采用部分熔化法在流氧气氛的旋转炉中 ,以 Ag箔为衬 ,成功制得直径 60 mm的 Bi- 2 2 1 2超导圆筒。加热初始粉到部分熔融状态 ,然后再冷却到 855℃以形成超导相 ,在富 N2 气氛下退火 ,并且从 70 0℃开始在纯 N2 气氛中冷却 ,这种工艺可以得到较好机械强度和外型的筒。XRD图象表明 Bi- 2 2 1 2筒中主要相为 Bi- 2 2 1 2超导相。 Bi- 2 2 1 2筒的临界电流密度为 1 0 0 Acm-2 ,Ic约为1 0 A 相似文献
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We have substituted 1.5% of Fe for Cu in several “2212” and “2223” Bi-Sr-Ca-Cu superconductors. All of the samples show a reduction ofT c about 13 K due to the Fe impurities. Mössbauer measurements at room temperature reveal the structural characteristics such as stacking faults and intergrowth of different phases in these Bi-based compounds on the microscopic scale. The susceptibility ofT c to Fe-doping in the Bi-“2212” or “2223” system is comparable to that of the “123” system but much smaller than that of the “214” system. The interplanar correlation existing in the “123” and the Bi-“2212” and “2223” systems seems to play an important role in sustaining the high temperature superconductivity and weakening the detrimental effect of impurity elements on superconductivity in these two systems. 相似文献
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The oxygen nonstoichiometry and high temperature conductivity of Bi2.12Sr1.86Cu1.02Oy (2201 phase) were determined as a function of temperature (T) and oxygen partial pressure (PO2). The dependences of conductivity on T and PO2 were similar to those of oxygen content, and two subphases, and β, were found in such cases as 2212 and 2223 phases. From the result a close relationship was inferred between conductivity and oxygen content, and the mobility and carrier density were calculated. The carrier density of 2201 phase was smaller than those of the 2212 and 2223 phases. 相似文献
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用固相反应法合成了名义组分为Bi1.92Pb0.32Sr2Ca1.7Mg0.3Cu3.07Ox的块状样品。X射线衍射谱(XRD)、扫描电子显微镜(SEM)和电子探计X射线分析(EDAX)结果以及块状和粉状试样的交流磁化率测量表明,样品中存在110和85K两个超导相;2223相(110K)首先在2212相(85K)晶体的晶界和外部区域生成。本文认为,最初存
关键词: 相似文献
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《Physica C: Superconductivity and its Applications》1999,311(1-2):107-121
The mechanism of Bi2Sr2CaCu2Ox (Bi-2212) crystallization from a partially molten state has been studied by means of thermal analysis, X-ray diffraction (XRD) measurement, and microstructural observation in Bi-2212/Ag tapes. Tapes have been prepared using the isothermal partial melting (IPM) method, under which partial melting and solidification are carried out at the same temperature in an nitrogen atmosphere and 20% oxygen partial pressure (p(O2)), respectively. The Bi-2212 phase crystallizes by peritectic reaction between (Sr, Ca)CuO2 (1:1 phase) and the liquid phase at processing temperatures (Tp)≥855°C. At the beginning of Bi-2212 crystallization, only the 1:1 and the liquid phases are present in tapes. The Bi-2212 nucleation occurs in the vicinity of 1:1 grains (homogeneous nucleation). This peritectic reaction progresses by recovery of oxygen in the liquid phase. In contrast, the nucleation of the Bi-2212 phase occurs heterogeneously at Tp≤850°C. The Bi-2212 phase co-exists with four Bi-free phases ((Sr, Ca)14Cu24O41 (14:24 phase), (Sr, Ca)2CuO3 (2:1 phase), (Sr, Ca)O (1:0 phase), and the 1:1 phase) and the liquid phase in the early stage of the Bi-2212 crystallization step. Since the precipitation temperature of the Bi-2212 phase is higher than 850°C, the Bi-2212 crystallization progresses by direct precipitation. The crystallization paths affect microstructure and transport critical current density (Jc) of Bi-2212 tapes. 相似文献
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Kai Kamada Shintaro Udo Shuichi Yamashita Yuko Tsutsumi Yasumichi Matsumoto 《Solid State Ionics》2003,160(3-4):389-394
Quantitative analysis of metal cation doping by solid oxide electrochemical doping (SOED) has been performed under galvanostatic doping conditions. A M–β″-Al2O3 (M=Ag, Na) microelectrode (contact radius: about 10 μm) was used as cation source to attain a homogeneous solid–solid contact between the β″-Al2O3 and doping target. In Ag doping into alkali borate glass, the measured dopant amount closely matched the theoretical value. High Faraday efficiencies of above 90% were obtained. This suggests that the dopant amount can be precisely controlled on a micromole scale by the electric charge during electrolysis. On the other hand, current efficiencies of Na doping into Bi2Sr2CaCu2Oy (BSCCO) ceramics depended on the applied constant current. Efficiencies of above 80% were achieved at a constant current of 10 μA (1.6 A cm−2). The relatively low efficiencies were explained by the saturation of BSCCO grain boundaries with Na. By contrast, excess Na was detected on the anodic surface of ceramics at a constant current of 100 μA (16 A cm−2). In the present study, we demonstrate that SOED enables micromole-scale control over dopant amount. 相似文献
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The optimised adhesion geometry and the work of adhesion were determined for the interface systems Al(001)/MgAl2O4(001) and Ag(001)/MgAl2O4(001) by ab-initio density-functional calculations. Al is bound strongly on-top of oxygen at reduced lattice spacing, whereas weak adhesion and no unique optimum structure are obtained for Ag. An analysis of the electronic structure shows that in both systems the metal-ceramic interaction is spatially confined to a narrow range along the interface layers. The weak adhesion of Ag on spinel is mediated by a polarisation of the metal film, which may be classified as an image-charge interaction. In the case of Al a weak image-charge contribution is dominated by a strong electron-density redistribution perpendicular to the interface, which leads to the formation of directional Al—O bonds. 相似文献
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X-ray powder diffraction, magnetic susceptibility and electrical resistivity measurements have been used to investigate the effect of Sn substitution in the Bi1.7Pb0.3Sr2Ca2(Cu3−xSnx1.2Oy system for different values of Sn concentrationx(0×1.33). The substitution of Sn is found to decrease the superconducting volume fraction of the 2223 phase. The 2212 phase is enhanced until it reaches a maximum at x=0.67. The system has a complete 2212 phase at x=0.88. An increase in the normal-state resistivity with a corresponding suppression of the temperature at which the resistivity goes to zero is observed with increasing x for the samples which are superconducting. The substitution of Sn probably causes a spatial disorder in the CuO2 planes, which in turn enhances the Coulomb interaction. Samples with x1.0 are found to be insulating. 相似文献