Crystallization in Fluoride Glasses Based on ZrF<sub>4</sub>-BaF<sub>2</sub> System

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  • MATUSITA Kazumasa
    Department of Materials Science and Technology, Technological University of Nagaoka
  • MIURA Kiyotaka
    Department of Materials Science and Technology, Technological University of Nagaoka HOYA Corporation
  • KOMATSU Takayuki
    Department of Materials Science and Technology, Technological University of Nagaoka

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Other Title
  • ZrF<sub>4</sub>-BaF<sub>2</sub>系フッ化物ガラスの結晶化
  • ZrF4 BaF2ケイ フッカブツ ガラス ノ ケッショウカ

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The non-isothermal crystallization kinetics in ZrF4-BaF2 and ZrF4-BaF2-NaF-AlF3 glasses were analyzed based on the method for determining the activation energy for crystal growth from DSC curves obtained at various heating rate. In binary system ZrF4-BaF2, most stable glasses were formed around the composition of 2 ZrF4⋅BaF2 (molar ratio) and the glass transition and crystallization temperatures increased as the glass composition approached to ZrF4⋅BaF2. It was found that the crystal particles grow two-dimensionally in thin film glass specimens. The activation energies for crystal growth were determined to be about 170 and 130kcal/mol in the composition range in which β-BaZrF6 and β-BaZr2F10 crystals precipitated respectively. In ZrF4-BaF2-NaF-AlF3 system, it was found that the crystal particles formed in the bulk specimens grow three-dimensionally and that the surface crystallization is predominant in powder specimens. The activation energies for crystal growth were below 120kcal/mol, much less than that for viscous flow. The crystallization mechanisms were discussed in detail.

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