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<p>The La<sub>2</sub>O<sub>3</sub>–Nb<sub>2</sub>O<sub>5</sub> binary system is a unique glass-forming system without conventional network former oxides, exhibiting two distinct glass-forming regions: La<sub>2</sub>O<sub>3</sub>-rich and Nb<sub>2</sub>O<sub>5</sub>-rich compositions. To evaluate its glass-forming ability, the temperature dependence of density, viscosity, and surface tension was measured using the electrostatic levitation furnace aboard the International Space Station (ISS–ELF). Melt density showed linear temperature dependence, and thermal expansion coefficients at 2000 K varied from 2.5 × 10<sup>−5</sup> to 4.0 × 10<sup>−5</sup> K<sup>−1</sup>. Substantial undercooling was observed for glass-forming compositions. Viscosity measurements above the melting point revealed that both La<sub>2</sub>O<sub>3</sub>-rich and Nb<sub>2</sub>O<sub>5</sub>-rich melts behave as fragile liquids. Activation energy derived from viscosity data was higher for glass-forming compositions. These results suggest that glass-forming ability can be assessed based on undercooling and activation energy across a wide compositional range, including non-glass-forming melts. The ISS–ELF experiments provide a valuable platform for understanding glass formation in systems inaccessible by terrestrial techniques.</p>

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Glass-forming ability of La2O3–Nb2O5 evaluated via thermophysical properties under microgravity

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月25日

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  • Atsunobu Masuno,
  • Chihiro Koyama,
  • Shinji Kohara,
  • Shunta Sasaki,
  • Satoshi Izumi,
  • Tomoharu Matsuya,
  • Yuki Mikami,
  • Kenta Yoshida,
  • Hirotaka Kobayashi,
  • Yuki Watanabe,
  • Akitoshi Mizuno,
  • Hirohisa Oda,
  • Yuta Shuseki,
  • Manabu Watanabe,
  • Junpei T. Okada,
  • Takehiko Ishikawa

摘要

The La2O3–Nb2O5 binary system is a unique glass-forming system without conventional network former oxides, exhibiting two distinct glass-forming regions: La2O3-rich and Nb2O5-rich compositions. To evaluate its glass-forming ability, the temperature dependence of density, viscosity, and surface tension was measured using the electrostatic levitation furnace aboard the International Space Station (ISS–ELF). Melt density showed linear temperature dependence, and thermal expansion coefficients at 2000 K varied from 2.5 × 10−5 to 4.0 × 10−5 K−1. Substantial undercooling was observed for glass-forming compositions. Viscosity measurements above the melting point revealed that both La2O3-rich and Nb2O5-rich melts behave as fragile liquids. Activation energy derived from viscosity data was higher for glass-forming compositions. These results suggest that glass-forming ability can be assessed based on undercooling and activation energy across a wide compositional range, including non-glass-forming melts. The ISS–ELF experiments provide a valuable platform for understanding glass formation in systems inaccessible by terrestrial techniques.