Growth of Dislocation-Free Crystals of High-Purity Niobium in Ultra High Vacuum

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  • Onose Utako
    The Research Institute for Iron, Steel and Other Metals, Tohoku University
  • Suezawa Masashi
    The Research Institute for Iron, Steel and Other Metals, Tohoku University
  • Imai Masato
    Graduate Student, Tohoku University
  • Sumino Koji
    The Research Institute for Iron, Steel and Other Metals, Tohoku University

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  • 超高真空中での高純度Nb無転位結晶の育成
  • チョウ コウ シンクウチュウ デ ノ コウ ジュンド Nb ム テンイ ケッシ

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Abstract

Dislocation-free crystals of high purity are needed for investigation of dynamic properties of dislocations. Kamada et al. succeeded to grow dislocation-free Nb crystals of diameters up to 0.5 mm in a vacuum of about 10−3 Pa. However, crystals with higher purity and larger dimensions are required for the above investigation.<BR>In the present work, the technique of Kamada et al. was improved by employing an apparatus for the crystal growth by the pedestal method operating in an ultra high vacuum of 10−7 Pa which avoided the contamination of growing crystals from surroundings. Using zone-refined and degassed high purity Nb polycrystalline rods as pedestals, crystals with arbitrarily controlled orientations have been grown with this apparatus. According to examinations by means of X-ray topography utilizing the Borrmann effect, dislocation-free Nb crystals of diameters up to 1.1 mm have successfully been grown at speeds of 6.7×10−6-12×10−6 m/s.

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