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Title: Optimization of a Non-arsenic Iron-based Superconductor for Wire Fabrication

Here we report on the optimization of synthesis of iron selenide-based superconducting powders and the fabrication of selenide-based wire. The powders were synthesized by an ammonothermal method, whereby Ba is intercalated between FeSe layers to produce Ba x(NH 3) yFe 2Se 2, with tetragonal structure similar to AFe 2X 2 (X: As, Se), '122', superconductors. The optimal T c (up to 38 K) and Meissner and shielding superconducting fractions are obtained from the shortest reaction time (t) of reactants in liquid ammonia (30 min). With the increase of t, a second crystalline 122 phase, with a smaller unit cell, emerges. A small amount of NH 3 is released from the structure above ~200 °C, which results in loss of superconductivity. However, in the confined space of niobium/Monel tubing, results indicate there is enough pressure for some of NH 3 to remain in the crystal lattice, and thermal annealing can be performed at temperatures of up to 780 °C, increasing wire density and yielded a reasonable T c ≈ 16 K. Here, we report of the first successful wire fabrication of non-arsenic high-T c iron-based superconductor. We find that although bulk materials are estimated to carry critical current densities >100 kAmore » cm ₋2 (4 K, self-field), the current transport within wires need to be optimized (J c ~ 1 kA cm ₋2).« less
 [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [4] ;  [4] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division; Idaho National Lab. (INL), Idaho Falls, ID (United States)
  4. Hyper Tech Research, Inc., Columbus, OH (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Superconductor Science and Technology
Additional Journal Information:
Journal Volume: 28; Journal Issue: 4; Journal ID: ISSN 0953-2048
IOP Publishing
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; iron based superconductor; selenide wire; non arsenic
OSTI Identifier: