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Title: Significant enhancement of compositional and superconducting homogeneity in Ti rather than Ta-doped Nb3Sn

Nb3Sn wires are now very close to their final optimization but despite its classical nature, detailed understanding of the role of Ta and Ti doping in the A15 is not fully understood. Long thought to be essentially equivalent in their influence on Hc2, they were interchangeably applied. Here we show that Ti produces significantly more homogeneous chemical and superconducting properties. Despite Ta-doped samples having a slightly higher Tc onset in zero-field, they always have a wider Tc-distribution. In particular, whereas the Ta-doped A15 has a Tc-distribution extending from 18 down to 5-6 K (the lowest expected Tc for the binary A15 phase), the Ti-doped samples have no A15 phase with Tc below ~12 K. The much narrower Tc distribution in the Ti-doped samples has a positive effect on their in-field Tc-distribution too, leading to an extrapolated μ0Hc2(0) 2 Tesla larger than the Ta-doped one. Ti-doping also appears to be very homogeneous even when the Sn content is reduced in order to inhibit breakdown of the diffusion barriers in very high Jc conductors. As a result, the enhanced homogeneity of the Ti-doped samples appears to result from its assistance of rapid diffusion of Sn into the filaments and by its incorporationmore » into the A15 phase interchangeably with Sn on the Sn sites of the A15 phase.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Florida State Univ., Tallahassee, FL (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
OSTI Identifier:
1235920
Grant/Contract Number:
SC0012083; AC02-98CH10886
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 108; Journal Issue: 4; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Florida State Univ., Tallahassee, FL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
National Science Foundation, Arlington, VA (United States). National High Magnetic Field Laboratory
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY Nb3Sn wire; doping effect; Tc distribution; chemical homogeneity