Papers by Keyword: Superconductor

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Authors: Dan Min Liu, Min Liu, Wei Qiang Xiao, Xue Dong Xu, Wei Liu, Mei Ling Zhou
Abstract: YBa2Cu3O7-δ(YBCO) films with highly biaxial textures were deposited on SrTiO3 single crystal, textured polycrystalline Ag and NiO/Ni substrates using pulsed laser deposition, metal-organic decomposition and ultrasonic spray pyrolysis method. The microstrains in different specimens with strong textures were measured using x-ray diffractometer and were compared each other.
696
Authors: Azhan Hashim, Shaari Abdul Halim, A. Nazree, Azman Kasim, S.A. Senawi
Abstract: Measurements of complex AC susceptibility χ = χ + χ as a function of temperature have been carried out on Sn-doped Bi1.6Pb0.4Sr2(Ca1-xSnx)2Cu3Oδ superconductor samples prepared via the conventional solid state reaction method. All the samples exhibit perfect diamagnetism below 109 K. The χ (T) curves display two-step features, indicating the presence of mixed phases and therefore weakening of the grains' coupling. The amount of shielded volume in Sn-free samples is greater than that in Sn-doped samples. The intrinsic peak due to the small AC losses within the grain was not observed in the χ (T) curves for all samples. However, the coupling peak, TP, for Sn-free samples at an applied field of 1.0 Oe was observed at 89 K and shifted to a lower temperature ranging from 59 K to 64.2 K in Sn-doped samples. The amounts of hysteresis losses above the TP in all doped samples were smaller than that of the Sn-free sample. Therefore, the effect of Sn doping suppressed the inter-granular critical current, Jcm, and the presence of weak links that coupled the superconducting grains.Keywords: BSCCO, AC Losses, Sn-doped, Superconductor
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Authors: Katsuyoshi Hotta, Hiroyuki Shimizu, Y. Watanabe, Haruo Hirose
Abstract: The purpose of this study is to examine the basic characteristics of the single layer type microwave absorber in X band. Samples were produced from Bi system (2223) superconductor powder and metallic powder and inserted into a wave guide system where the complex reflection intensity was measured (The short circuit method) by using the vector network analyzer[1]. As the result, at the room temperature (300K), the reflection loss is apt to increase with increasing the content of the Bi system superconductor powder. Furthermore, the measured value of the reflection loss agreed with the value calculated from the complex permittivity εr* . At liquid nitrogen temperature (77K) where the superconductor powders are in the superconducting state, some differences occurred between the calculated value and the measured one of the reflection loss. For the metallic powders, copper powder showed good agreement between the calculated and the measured of reflection loss. For the magnetic material, it was concluded that the theoretical formula under consideration of complex permeability μr* should be derivated.
93
Authors: Natacha Andréia Nogueira, Anne Hitome Yonamine, Dayse Iara dos Santos, Jung Ho Kim, Shi Xue Dou
Abstract: The addition of two compounds, calcium silicate and calcium zirconate was tested, in the preparation of Bi: 2212 silver sheathed wires by powder-in-tube method, which were successfully tested previously in processing chips. The wires were treated in an atmosphere of O2/Ar using partial melting method. The characterizations were structural and on their electrical and magnetic properties. As the results, transition temperatures were higher than the expected for this stage, ranged from 105K (BSCCO880) to 116K (+Si883). The critical current densities encountered in transport and magnetization measurements were improved in comparison with the wires without addition.
106
Authors: Isabel Van Driessche, G. Penneman, J.S. Abell, E. Bruneel, Serge Hoste
3517
Authors: E. Guilmeau, Daniel Chateigner, J. Noudem, B. Ouladdiaf
Abstract: Orientation distributions of polyphased (Bi,Pb)2Sr2Ca2Cu3O10+d superconducting textured materials are determined from neutron diffraction analysis. The quantitative texture analysis of neutron data was accomplished by using the combined Rietveld-WIMV-Popa algorithms, implemented in the program package Materials Analysis Using Diffraction (MAUD). Curved position-sensitive detector and 4-circle diffractometry allow the whole diffraction pattern treatment. Transport critical current densities, measured on different samples, are strongly dependent of the calculated texture strengths, crystallite sizes and phase ratios. The results prove the interest of the combined approach for a quantitative texture analysis of complex materials. Texture to anisotropic physical properties relationship is discussed.
385
Authors: Hassan Nurul Hidayah, S.Y.S. Yahya, H. Azhan, K. Azman, J.S. Hawa, A.W. Norazidah
Abstract: The comparison substitution with K, Ca and Zn respectively at the Cu site of YBa2Cu3-xMxOδ (x = 0.00 and 0.20) was performed based on superconducting and structural properties. All samples were prepared via a solid state technique. Resistivity and current density measurements (zero magnetic fields) were done using the four probe method and the structural and morphological properties were characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) respectively. The critical current density (Jc) and critical temperature (Tc zero) of the substituted samples were found to be lower than that of the pure sample. Tc zero with K and Zn substitution was 78 K and 21 K respectively. This is due to the change in the hole concentration. Jc measured at 50 K showed values of 3.9790 A/cm2, 4.4483 A/cm2 and 2.9854 A/cm2 for the pure sample, K and Ca substituted samples respectively. The decrease in Jc was due to the hole porosity and grain connection. All samples showed an orthorhombic crystal structure. The morphology of the fracture surface of samples as observed by FESEM displayed a loose structure of grain arrangement for sample Ca and Zn substituted samples.
79
Authors: Pascal Tixador
Abstract: After the emergence of AC NbTi strands, superconducting transformers were successfully built. But the very high cost of 4 K cryogenics made these transformers economically not attractive. The high Tc superconductors (HTS), operating at much higher temperatures, change these conclusions with low cost HTS conductors. The high cost of PIT tapes and the relatively large AC losses remain issues. The second generation HTS wires, the REBCO coated conductors, are under development and achieved substantial progress recently. They operate at higher temperatures and intrinsically show lower AC losses especially for transformers. MgB2 is the third option. The magnetic flux density conditions make possible the operation at 27 K and they show low costs. This paper provides a preliminary design for an on-board 40 MVA transformer using YBCO coated conductors and MgB2 wires. Both superconducting transformers show similar volume and weight. The power density per unit mass and volume is improved by a factor about two, cryogenic included, compared to resistive systems. This makes them very attractive for on-board mobile systems. The economical point of view will be discussed based on some targets price/performance for superconductors and cryocoolers. MgB2 is penalized by its operation at lower temperature (27 K / 77 K), which makes cryogenics very expensive. The advantage of the low cost of MgB2 compared to REBCO may be lost except with very low AC loss MgB2 tapes.
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