Hydrostatic Compression Effects on Fifth-Group Element Superconductors V, Nb, and Ta Subjected to High-Pressure Torsion

  • Mito Masaki
    Graduate School of Engineering, Kyushu Institute of Technology
  • Shigeoka Shun
    Graduate School of Engineering, Kyushu Institute of Technology
  • Kondo Hirotaka
    Graduate School of Engineering, Kyushu Institute of Technology
  • Noumi Nozomi
    Graduate School of Engineering, Kyushu Institute of Technology
  • Kitamura Yuichiro
    Graduate School of Engineering, Kyushu Institute of Technology
  • Irie Kunihiko
    Graduate School of Engineering, Kyushu Institute of Technology
  • Nakamura Kazuma
    Graduate School of Engineering, Kyushu Institute of Technology
  • Takagi Seishi
    Graduate School of Engineering, Kyushu Institute of Technology
  • Deguchi Hiroyuki
    Graduate School of Engineering, Kyushu Institute of Technology
  • Tajiri Takayuki
    Faculty of Science, Fukuoka University
  • Ishizuka Mamoru
    Center for Scientific Instrument Renovation and Manufacturing Support, Osaka University
  • Nishizaki Terukazu
    Department of Electrical Engineering, Kyushu Sangyo University
  • Edalati Kaveh
    Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University
  • Horita Zenji
    Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University

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Abstract

<p>In fifth-group element superconductors V, Nb, and Ta, the increase in superconducting transition temperature (Tc) was attempted by using both high-pressure torsion (HPT) and additional hydrostatic pressure (HP) compression. The former brings about the grain refinement and strain accumulation in the unit-cell level. The additional compression for severely strained superconductors triggers strengthening intergrain-contact and/or structural deformation in the unit-cell level. The manner of the appearance of the above two effects depends on the kind of elements: First, in V, there is no prominent effect of HPT, comparing to the hydrostatic compression effects on its non-strained material. Next, in Ta, the effect of strengthening intergrain-contact appears at small hydrostatic compression, resulting in temporal increase in Tc. Finally, Nb exhibits prominent increase in Tc by both effects and, in particular, the structural deformation in the unit-cell level promotes the increase in Tc. Thus, the accumulation of residual strain in the level of starting material can be a promising work to manipulate Tc under HP compression.</p>

Journal

  • MATERIALS TRANSACTIONS

    MATERIALS TRANSACTIONS 60 (8), 1472-1483, 2019-08-01

    The Japan Institute of Metals and Materials

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