| Project/Area Number |
12650012
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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 |
Applied materials science/Crystal engineering
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| Research Institution | Nagoya University, Associate Professor, Research Associate |
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Principal Investigator |
IKUTA Hiroshi Center for Integrated Research in Scienc. And Engineering, AssofTiate Professor, 理工科学総合研究センター, 助教授 (30231129)
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| Co-Investigator(Kenkyū-buntansha) |
BIWA Tetsushi Graduate School of Engineering. Deoartment of Crystalline Materials Science,Research Associate, 大学院・工学研究科, 助手 (50314034)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2001: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2000: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | high temperature superconductor / melt-processed bulk superconductor / trapped field / mechanical strength / microstructure / REBa8Cu307 / diffusiyity of oxygen / CeO.-addition / Yba_2Cu_3O_7 / (Nd, Eu, Gd)Ba_2Cu_3O_7 / DyBa_2Cu_3O_7 / SmBa_2Cu_3O_y / NdBa_2Cu_3O_y / 空孔除去 |
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| Research Abstract |
The superconducting properties of bulk high temperature superconductors, such as the trapped field, had already reached a very high level. However, it has been commonly observed that the samples are easily broken by the magnetic pressure of the trapped fluxes or by an abrupt heat cycling. The microstructure of melt processed.bulk superconductors is influenced by the contents of each phase as well as by the preparation condition, which in turn affects the fracture toughness. Therefore, we prepared samples by varying the composition and preparation condition, and examined the microstructure and the fracture toughness. The major results are summarized in the following.
We succeeded in the preparation of a single-grain, c-axis aligned, Nd-based bulk superconductor that is 30 mm in diameter for the first time. The trapped field was larger than that of a Sm-based sample that contains the same amount of Ag. We also studied the relation between the atmosphere during the melting and the formatio
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n of voids, and succeeded in the elimination of voids by melt-processing the samples in an oxygen-gas flowing atmosphere or vacuum. It was also confirmed that the samples show high performance if the atmosphere were switched to an Ar-gas flowing one during the growth process. The average particle size of the Sm211 phase in a sample prepared with 211-phase powders that were treated with ball-milling was 0.7 ^m, and the trapped field increased compared to samples prepared with the same condition using 211-phase powders that were not ball-milling treated.
We also studied the oxygenation process of Sm- and Y-based samples to establish an efficient oxygen treatment for dense samples. It was found that the diffusivity of oxygen is influenced by the difference in the microstructure rather than the difference of the system, Ag-added samples require a longer oxygen treatment because of the less amount of voids, and a low temperature treatment below 350aC is important for Sm-based samples. We established the melt-processing conditions of the Nd-Eu-Gd system up to 36 mm in diameter, for which the trapped field was 1.4 T at liquid nitrogen temperature and 8.2 T at 20 K. For the Dy-based system, the trapped field reached 5.7 T at 18 K even with a small sample whose diameter was 18 mm, and the trapped field of a CeO2-added Y-based sample that is 18 mm in diameter reached 6.2 Tat25K. Less
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