Nucleation-Controlled Phase Selection in Rapid Solidification from Undercooled Melt of DyMnO<sub>3</sub>

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  • Hayasaka You
    Graduate School of Engineering, Chiba Institute of Technology
  • Kuribayashi Kazuhiko
    Research Liaison Centre, Chiba Institute of Technology Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)
  • Shiratori Suguru
    Department of Mechanical Systems Engineering, Faculty of Engineering, Tokyo City University
  • Ozawa Shumpei
    Department of Advanced Materials Science and Engineering, Chiba Institute of Technology

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Other Title
  • DyMnO<sub>3</sub>の過冷却融液からの急速凝固における核形成律速相選択
  • DyMnO₃の過冷却融液からの急速凝固における核形成律速相選択
  • DyMnO ₃ ノ カレイキャクユウエキ カラ ノ キュウソク ギョウコ ニ オケル カク ケイセイ リッソクソウ センタク
  • Nucleation-Controlled Phase Selection in Rapid Solidification from Undercooled Melt of DyMnO₃

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<p>The equilibrium crystal structure of LnMnO3 (Ln: lanthanide) has been reported to be orthorhombic when La3+ to Dy3+ are used as Ln3+, and hexagonal when Ho3+ to Lu3+ are used. Whereas Kumar et al. reported a two-phase structure of orthorhombic and hexagonal phases is formed in DyMnO3 when it was solidified from the undercooled melt under containerless state. The reason for the formation of the two-phase structure was not thoroughly addressed and discussed. We investigated the formation mechanism for the two-phase structure from the undercooled melt of DyMnO3 in detail. As a result, the surface morphology, microstructure, and crystal structure of the samples, in which the nucleation was forced at a predetermined temperature with a Mo needle, indicated that the hexagonal and orthorhombic phases are dominant at high and low temperatures, respectively. When the sample was quenched from below 1670 K in a water bath, as-solidified sample consisted of h-DyMnO3 and o-DyMnO3. Whereas a single phase of h-DyMnO3 was obtained in the sample quenched from above 1670 K. This phenomenon can be quantified in terms of nucleation-rate determined phase selection. That is, the activation energy for forming a critical nucleus calculated based on the model of the crystal-melt interface proposed by Turnbull and Speapen suggests that the o-DyMnO3 phase can be heterogeneously nucleated on the interface of the initially formed h-DyMnO3 phase.</p><p> </p><p>This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 85 (2021) 155–161. The abstract and captions of Figs. 1–10 are modified.</p>

Journal

  • MATERIALS TRANSACTIONS

    MATERIALS TRANSACTIONS 62 (7), 982-987, 2021-07-01

    The Japan Institute of Metals and Materials

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