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2007 Fiscal Year Final Research Report Summary

Positron lifetime study on vacancy behavior in bcc-base intermetallics

Research Project

Project/Area Number 18560644
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Physical properties of metals
Research InstitutionOsaka University

Principal Investigator

ARAKI Hideki  Osaka University, Greduate School of Engineering, Associate professor (20202749)

Co-Investigator(Kenkyū-buntansha) SHIRAI Yasuharu  Osaka University, Graduate School of Engineering, Professor (20154354)
MIZUNO Masataka  Osaka University, Graduate School of Enineering, Assistant Professor (50324801)
Project Period (FY) 2006 – 2007
Keywordspositron / positron annihilation / positron lifetime / vacancy / intermetallics
Research Abstract

The bcc-base intermetallic compound, Co_2TiAl, is expected to be useful as a coating material on refractory material, because it maintains L2_1-type ordered structure up to high temperature and has excellent oxidation resistance. The Co_2TiAl phase has a wide composition range, extending across the stoichiometric composition and hence constitutional defects have to be naturally introduced at non-stoichiometric compositions. However, the defect structure has not been revealed yet. In this work we have measured the positron lifetimes in Co-rich and Al-rich Co_2TiAl water-quenched or furnace-cooled from 1273K. The positron mean lifetime in the water-quenched Co_<50.8>Ti_<24.0>Al_<25.2> is about 160ps and nearly equal to that in the furnace-cooled Co_<50.8>Ti_<24.0>Al_<25.2>, but is much larger than about 120ps of the first-principles calculated positron lifetime in the perfect lattice, Co_<50>Ti_<25>Al_<25>. For both the water-quenched and furnace-cooled specimens, χ^2q^<-1>, which is proportional to the square of the difference between the experimentally obtained spectrum and the fitted decaying function of one lifetime component, is close to unity, which can be interpreted as due to the saturation trapping of positron by vacancy. These results clearly show that many vacancy of more than 10^<-4> atomic fraction is introduced in Co-rich and Al-rich Co_2TiAl, in order to compensate the deviation from the stoichiometry.

  • Research Products

    (4 results)

All 2007 2006

All Journal Article (4 results) (of which Peer Reviewed: 3 results)

  • [Journal Article] Thermal formation of vacancies in Cu_3Sn2007

    • Author(s)
      Itsurou Shishido
    • Journal Title

      Physica Status Solidi(c) 4

      Pages: 3563-3566

    • Description
      「研究成果報告書概要(和文)」より
    • Peer Reviewed
  • [Journal Article] Positron lifetime study on the degradation of LaNi_5 and LaNi_<4.8>Sn_<0.2> during hydrogen absorption-desorption cycling2007

    • Author(s)
      Hideki Araki
    • Journal Title

      Physica Status Solidi(c) 4

      Pages: 3510-3513

    • Description
      「研究成果報告書概要(和文)」より
    • Peer Reviewed
  • [Journal Article] First Principles Calculation of Defect and Magnetic Structures in FeCo2006

    • Author(s)
      Masataka Mizuno
    • Journal Title

      Materials Transactions 47

      Pages: 2464-2650

    • Description
      「研究成果報告書概要(和文)」より
    • Peer Reviewed
  • [Journal Article] First principles Calculation of defect and magnetic structure in FeCo2006

    • Author(s)
      Masataka Mizuno
    • Journal Title

      Materials Transactions 47

      Pages: 2464-2650

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 2011-06-18  

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