Developments of (Ba,Na)Fe2As2and CaKFe4As4HIP round wires

T. Tamegai, S. Pyon, D. Miyawaki, Y. Kobayashi, S. Awaji, H. Kito, S. Ishida, Y. Yoshida, K. Takano, H. Kajitani, N. Koizumi

Research output: Contribution to journalArticlepeer-review

Abstract

With excellent superconducting properties such as high T c, large H c2, small anisotropy, and large J c, developments of superconducting wires and tapes of iron-based superconductors (IBSs) have been undertaken with promising results. So far, K-doped 122-type IBSs have been mainly developed for such purposes. Here, efforts to fabricate Na-doped 122-type IBS, (Ba,Na)Fe2As2, are presented. With the help of hot isostatic pressing (HIP) process, excellent J c characteristics of up to 44 kA cm-2 at 4.2 K under 100 kOe have been achieved. Detailed characterizations of (Ba,Na)Fe2As2 HIP round wire are presented. On the other hand, discoveries of new IBSs continue, with CaKFe4As4 as one of recent examples. CaKFe4As4 belongs to a new family of IBSs with 1144 structure, where Ca and K occupy the Ba site in BaFe2As2 alternately along the c-axis. Studies on CaKFe4As4 single crystals have demonstrated moderately large J c with peculiar anisotropic properties related to the presence of novel planar defects. We have also fabricated HIP round wires of CaKFe4As4, and reported their basic characterizations. Despite the instability of CaKFe4As4 at low temperatures, J c values at 4.2 K close to 100 kA cm-2 at self-field and 7.6 kA cm-2 at 100 kOe are achieved. Attempts to introduce defects into CaKFe4As4 single crystals, chemically by Co substitution and physically by proton irradiation, are attempted, and the effects are compared. Attempts to fabricate Co-doped CaKFe4As4 HIP round wires with limited success are also reported.

Original languageEnglish
Article number104001
JournalSuperconductor Science and Technology
Volume33
Issue number10
DOIs
Publication statusPublished - 2020 Oct

Keywords

  • (Ba,Na)FeAs
  • CaK(Fe,Co)As
  • CaKFeAs
  • critical current density
  • iron-based superconductor
  • planar defects
  • superconducting wire

ASJC Scopus subject areas

  • Ceramics and Composites
  • Condensed Matter Physics
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry

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