High-Field Nb3Sn Superconductors Prepared through a New Route
Nb3Sn superconductors have been prepared through Nb6Sn5 compound powder synthesized by a melt diffusion process from Nb and Sn powders. The Nb6Sn5 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 Nb6Sn5 and Nb powder promotes the formation of A15 Nb3Sn phase in the subsequent heat treatment, and improves superconducting performance. The NbsSn tape shows an upper critical field Bc2 of nearly 25T at 4.2K after the reaction at 900°C. The Bc2 is still increased by Ti doping. A small amount of Cu addition decreases the optimum reaction temperature to 850°C. Present Nb3Sn specimen exhibits considerably larger normal state resistivity than that of bronze-processed M>3Sn, which may be the origin of enhanced Bc2 in the present Nb3Sn specimen.
KeywordsCritical Current Density Mixed Powder Subsequent Heat Treatment Bulk Specimen Magnetic Field Curve
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