| Project/Area Number |
06650787
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Structural/Functional materials
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| Research Institution | Tokai University |
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Principal Investigator |
TACHIKAWA Kyoji Tokai University, Faculty of Engineering, Professor, 工学部, 教授 (40197372)
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| Co-Investigator(Kenkyū-buntansha) |
YAMADA Yutaka Tokai University, Faculty of Engineering, Professor, 工学部, 教授 (10266372)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1995: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1994: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | superconductors / Nb_3Sn / Nb_3 (Al, Ge) / intermadiate compound / mechanical alloying / upper critical field / critical current density / Ti添加 / Cu添加 |
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| Research Abstract |
Nb_3Sn superconductors have been prepared through Nb_6Sn_5 intermediate compound powder synthesized by a melt diffusion process from Nb and Sn powders. The Nb_6Sn_5 powder was mixed with Nb powder in a ball mill. The resulting mixed powder was encased in a Ta tube, and fabricated into a tape. The mechanical mixing of Nb_6Sn_5 and Nb powders appreciably promotes the formation of A15 Nb_3Sn phase in the subsequent heat treatment, and improves the superconducting performance. The Nb_3Sn tape shows an upper critical field Bc_2 of nearly 25T at 4.2K after the reaction at 900ﾟC.Present Nb_3Sn specimens exhibit large normal state resistivity which may be the origin of enhanced Bc_2 in the present Nb_3Sn. The Bc_2 is still increased by the Ti doping. A small amount of Ge addition improves critical current Jc in high fields. A Jc of 2.5*10^4A/cm^2 has been obtained at 21T and 4.2K.Meanwhile, a small amount of Cu addition decreases the optimum reaction temperature to 850ﾟC.
A15 Nb_3 (Al, Ge) tapes have been fabricated through a similar process starting from sigma phase Nb_2 (Al, Ge) powder. The mechanical mixing of sigma phase and Nb powders improves the high-field performance of Nb_3 (Al, Ge) tape. A Jc of over 2.7*10^4A/cm^2 at 23T and 4.2K has been obtained after the reaction at 1300ﾟC.The Nb_3 (Al, Ge) tape shows high-field performance superior than that of the Nb_3Sn tape, however, the latter seems to be more promising from practical view point due to its lower reaction temperature. Present research has succeeded in preparing A15 superconductors capable of generating 20T at 4.2K through a new process.
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