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Low-Temperature Electron Microscopy on the Cubic-Tetragonal Transformation of V_3Si and Nb_3Sn

Research Project

Project/Area Number 62550469
Research Category

Grant-in-Aid for General Scientific Research (C)

Allocation TypeSingle-year Grants
Research Field Physical properties of metals
Research InstitutionTOHOKU UNIVERSITY

Principal Investigator

ONOZUKA Takashi  Associate assistant, Institute for Materials Research, Tohoku Univ., 金属材料研究所, 助手 (10005936)

Co-Investigator(Kenkyū-buntansha) KAJITANI Tsuyoshi  Associate assistant, Institute for Materials Research, Tohoku Univ., 金属材料研究所, 助手 (80134039)
HIRABAYASHI Makoto  Professor, Institute for Materials Research, Tohoku Univ., 金属材料研究所, 教授 (00005836)
Project Period (FY) 1987 – 1988
Project Status Completed (Fiscal Year 1988)
Budget Amount *help
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,400,000 (Direct Cost: ¥1,400,000)
KeywordsA15 compounds / High-Tc superconducting ceramic / Phase Transformation / Precursor / 低温電子顕微鏡観察 / 低温電子顕微鏡 / 超電導化合物
Research Abstract

Structural phase transformations of V_3Si and La_<2-x>Sr_xCuO_4(0.11<greater than or equal>x<greater than or equal>0.18) have been investigated in the temperature range from 8K to room temperature using a 1 MV electron microscope with a double-tilt goniometer cooled by liquid helium and a 200kV electron microscope with a side-entry stage cooled by liquid nitrogen.
The cubic-tetragonal trnasformation of V_3Si takes place at a temperature tm<similar or equal>19K. A remarkable softening of the shear modulus occurs with decreasing temperature down to near Tm, and is ascribed to a precursor of the cubic-tetragonal^- transformation. Below the transformation temperature, fine twin lamellae appear parallel to {110} plane traces, being connected continuously with mottled striations having the same orientation. Fine striations along {110} traces or socalled tweeds are observed below 50K at the precursor of the structural phase transformation. The image contrast of mottled striations and tweed pat … More terns is attributed to the presence of lattice distortion owing to the softening of the shear modulus. Reversible changes of the patterns recorded with a TV-VTR system during cooling and heating process are discussed briefly.
The doped oxides La_<2-x>Sr_xCuO_4 are a family of high-Tc superconducting ceramics, having the superconducting temperature Tc=38K at x=0.15. Those materials undergo a tetragonal-orthorhombic phase transformation which is suppressed by Sr-doping. The occurrence of another phase transformation which is suppressed by Sr-doping. The occurrence of another phase transformation has been suggested by single crystal X-ray studies of La_<1.85>Sr_<0.15>CuO_4. In La_<1.85>Sr_<0.15>CuO_4, twin lamellae associated with the tetragonal-orthorhomblc phase transformation appear quite continuously on cooling in the temperature range of 120K-160K. Its reverse process is observed on heating. Observations of x=0.11, 0.15 and 0.18 down to 8K did not detect any phase transformation in the orthorhombic phase. A tentative phase diagram of La_<2-x>Sr_xCuO_4 is proposed. Less

Report

(2 results)
  • 1988 Annual Research Report   Final Research Report Summary
  • Research Products

    (9 results)

All Other

All Publications (9 results)

  • [Publications] T.Onozuka.: Jpn.J.Appl.Phys.26. L1711-1714 (1987)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1988 Final Research Report Summary
  • [Publications] T.Onozuka.: Metall.Trans.19. 797-801 (1988)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1988 Final Research Report Summary
  • [Publications] T.Onozuka.: Proc.MRS Int.Meetins on Advanced Materials. (1987)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1988 Final Research Report Summary
  • [Publications] T. Onozuka: "A Low-Temperature Electron Microscopy and Electron Diffraction Study of La_<1.84>Sr_<0.16>CuO_4" Japanese Journal of Applied Phusics. 26. 1711-1714 (1987)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1988 Final Research Report Summary
  • [Publications] T. Onozuka: "Low-Temperature Electron Microscopy on the Cubic-Tetragonal Transformation of V_3Si" Metallurgical Transactions. 19. 797-801 (1988)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1988 Final Research Report Summary
  • [Publications] T. Onozuka: "Electron Microscopy on the Structunal Transformation of La_<2-x>Sr_xCuO_4" Proceedings of MRS International Meeting on Advanced Materials. (1989)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1988 Final Research Report Summary
  • [Publications] Takashi,Onozuka: Japanese Journal of Applied Physics. 26. 1711-1714 (1987)

    • Related Report
      1988 Annual Research Report
  • [Publications] Tsuyoshi,Kajitani: Japanese Journal of Applied Physics. 26. 1877-1880 (1987)

    • Related Report
      1988 Annual Research Report
  • [Publications] Takashi,Onozuka: Metallurgical Transactions.

    • Related Report
      1988 Annual Research Report

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Published: 1987-04-01   Modified: 2016-04-21  

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