| Project/Area Number |
08650796
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Composite materials/Physical properties
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
YOSHIDA Katsukuni Kyoto University, Graduate School of Energy Science, Professor, エネルギー科学研究科, 教授 (70027142)
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| Co-Investigator(Kenkyū-buntansha) |
UEDA Sizumasa Kyoto University, Institute of Advanced Energy, Research Associate, エネルギー理工学研究所, 助手 (00093196)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1996: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | percolation / cluster / high-To cuprates / superconductivity / composites / critical exponents / 高温超伝導 / 臨界温度 / 閾値 / パーコレーション閾値 / 銀添加Bi系複合材料 |
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| Research Abstract |
In order to reveal the relationship between the superconducting characteristics and the textural structures in two-phase superconducting composites, the percolation process describing the critical behavior of the cluster structures has been investigated. The first half of this study was performed for the composite of metallic Ag phase and Bi-based cuprate consisting of 2223 phase having the critical temperature T_c=110K.The superconducting characteristics are strongly featured by the structural behavior exhibiting the percolation transition, for which the critical exponents for Ag cluster were found as t=1.1 and s=0.66 together with the percolation threshold f_c(Ag)=0.25, indicating 3 dimensional(3D)growing of Ag clusters. On the other hand, superconducting cuprate phase shows 2D growth, which is elicited from the observed values of the critical exponent s=1.2 and the threshold f_c(cuprate)=0.56. This variance between two phases originates from the difference in the morphology of the constituent grains. The latter half of the study was devoted to elucidation of the superconducting properties of Pr-doped Y_1Ba_2Cu_3O_<7-delta>, where impurity Pr acts as a detrimental on the superconductivity. The percolation process takes place on nanometer scale, and features well the superconducting characteristics, showing thresholds around x=0.6 and 0.4, which are characteristic of 2D site-percolation systems. In summary, the percolation parameters shown above are effective in characterizing the composites in reference to the structural features.
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