外部電場印加による非調和融解状態の調和融解化 : 非調和融解ランガサイト結晶の調和融解成長  [in Japanese] Electric-field Assisted Conversion of the Incongruent-melting State to the Congruent-melting State for the Growth of Langasite  [in Japanese]

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Abstract

ランガサイト(La_3Ga_5SiO_<14>)は,非調和融解物質であるが,ランガサイト種子結晶を使用すると適切な過冷却度のもとにいわゆる擬似調和融解融液から直接単結晶を育成することができる.しかしながら,非調和融解性に起因する多結晶化が育成中に頻繁に発生するという深刻な問題がある.この問題を根本的に解決するには,ランガサイトの非調和融解状態を何らかの方法で調和融解状態に変換する必要がある.成長系に外部電場を印加すると関連する平衡共存相の化学ポテンシャルの修飾によりエネルギー関係が変わり,非調和融解状態が調和融解状態に変わる可能性がある.たとえば,ランガサイトは,600V/cmの電界下で調和融解状態に変換される.これは,融液と初晶相(Gaを含むランタンシリケート相)の共存状態とランガサイト組成の融液の自由エネルギーの大きさの関係が電場により逆転するからである.このような変換の可能性は,これらの相の誘電率の変化が初晶相側端成分に向かって増加する場合に見られる.

Although langasite (La_3Ga_5SiO_<14>) is an incongruent-melting material, it can directly grow from the "pseudo-congruent melt" via the Czochralski method using a langasite seed crystal when the appropriate supercooling is provided. However, polygonization due to the incongruency of langasite during growth is still a serious problem. To completely prevent from such a defect, the incongruency must convert to the congruency by some manners. The imposition of an external electric field on a growth system changes the chemical potentials of associated phases in equilibrium which could convert the incongruent-melting state into congruent-melting state. Langasite in the ternary system of L_a2O_3-Ga_2O_3 SiO_2, became congruent-melting under an external electric field of 600V/cm. This conversion was attributed to the inversion of the stability relationship in terms of the molar free energy between the primary phase in equilibrium with liquid and the liquid phase at the composition of langasite. Such a transformation is generally possible when the electrical permittivities of liquid, primary phase and incongruent-melting material increase toward the end component of the primary phase.

Journal

  • Journal of the Japanese Association for Crystal Growth

    Journal of the Japanese Association for Crystal Growth 32(4), 325-333, 2005

    The Japanese Association for Crystal Growth

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Codes

  • NII Article ID (NAID)
    110007327694
  • NII NACSIS-CAT ID (NCID)
    AN00188386
  • Text Lang
    JPN
  • Article Type
    REV
  • ISSN
    0385-6275
  • NDL Article ID
    7681701
  • NDL Source Classification
    ZM35(科学技術--物理学)
  • NDL Call No.
    Z15-339
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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