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Novel High-Temperature Superconductor with Reduced Rare-Earth Content (Press Release)

Release Date
14 Nov, 2013
  • BL02B1 (Single Crystal Structure Analysis)
- Reduction in rare-earth content using arsenic chains leads to low-cost production of superconducting wire rod -

Nagoya University
Okayama University

Key points
• Substantially reduced rare-earth content by substituting arsenic chains for rare-earth elements*1.
• Development of a novel superconductor with a high superconducting transition temperature, applicable to wire rods and magnets
• New guidelines for the design and development of superconductors

A research group in Nagoya University (President, Michinari Hamaguchi), in collaboration with Okayama University (President, Kiyoshi Morita), succeeded in developing a novel iron-based superconductor*2. This was achieved by Naoyuki Katayama (assistant professor), Seiichiro Onari (assistant professor) and Hiroshi Sawa (professor) of the Graduate School of Engineering, Nagoya University, and Kazutaka Kudo (associate professor), Minoru Nohara (professor), and other researchers of the Graduate School of Natural Science and Technology, Okayama University. A number of iron-based superconductors have been reported worldwide since their discovery because they have attracted attention owing to their high transition temperature. However, their high cost and high environmental load resulting from their high rare-earth content, which account for 25% of their constituent composition, have been one of the causes that prevent their application. In this research, novel superconductors were developed adopting a new idea of substituting the arsenic chains of the nitrogen group for the rare-earth elements. These superconductors have a novel crystal structure that has never been reported before, contain 5% rare-earth elements or less, and show a high transition temperature. These characteristics indicate a high possibility of practically applying the novel superconductors to superconducting wire rods and magnets.

"Superconductivity in Ca1-xLaxFeAs2: A Novel 112-Type Iron Pnictide with Arsenic Zigzag Bonds"
Journal of the Physical Society of Japan 82 123702 (2013)


Fig. 1	Crystal structure of novel iron-based superconductors (sandwich structure consisting of iron-arsenic layers and spacer layers).
Fig. 1 Crystal structure of novel iron-based superconductors
(sandwich structure consisting of iron-arsenic layers and spacer layers).

Top view of arsenic zigzag chains constituting the novel spacer layers is shown on the right. Bias in the electron distribution, owing to chemical bonds between arsenic atoms, is shown in colors.

Fig. 2		Electrical resistance of 112-based superconductors.
Fig. 2 Electrical resistance of 112-based superconductors.

The decrease in electrical resistivity, which is characteristic of superconducting transition, starts at 45K.

*1 Rare-earth elements

Elements such as samarium, neodymium, and europium. Rare-earth elements include many industrially important elements such as fluorescent substances and the raw materials of magnets. They are unevenly distributed on earth, and Japan depends on imports from China for 90% of its rare-earth needs. Recently, in response to the increase in the price of rare-earth elements, research effort is being exerted to realize “independence from rare-earth resources” through the cooperation between government and private sectors.

*2 Iron-based high-temperature superconductors
Novel high-temperature superconductors were discovered in Japan in 2008. They have attracted much attention and become an active focus of research because, until then, compounds containing ferromagnetic iron had been considered to show no superconductivity. Many derivatives of iron-based high-temperature superconductors have been found thus far and named after their chemical compositions. The current highest transition temperature ever recorded is 55 K in the 1111-based compound SmFeAsO1-xFx.

For more information, please contact:
  Assistant Prof. Naoyuki Katayama (Nagoya University)
    E-mail : mail1

  Assistant Prof. Seiichiro Onari (Nagoya University)
    E-mail : mail2

  Associate Prof. Kazutaka Kudo (OKAYAMA UNIVERSITY)
    E-mail : mail3