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<p>The growth of high-quality Na<sub>2</sub>Mo<sub>2</sub>O<sub>7</sub> single crystals, a promising scintillator material, is critically dependent on the precise knowledge of their melt’s thermophysical properties. However, obtaining the intrinsic thermal conductivity of high-temperature melts is notoriously challenging on Earth due to buoyancy-driven convection. Here, we report the first direct measurement of the thermal conductivity of molten Na<sub>2</sub>Mo<sub>2</sub>O<sub>7</sub>, accomplished by employing a self-developed transient hot-wire system aboard the China Space Station. The microgravity environment effectively suppressed convection, enabling accurate measurement within the 750–900&#xa0;°C range. Results reveal that the intrinsic thermal conductivity decreases monotonically from approximately 0.457 W/(m·K) to 0.416 W/(m·K) with increasing temperature, a trend attributed to the phonon-dominated conduction mechanism. In contrast, terrestrial measurements yielded systematically higher values (by 12.0–16.6%) due to convective contributions. This work not only fills a critical data gap for optimizing crystal growth but also establishes a robust methodology for probing the thermophysical properties of high-temperature melts in space.</p>

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In-orbit Measurement of Thermal Conductivity of Na2Mo2O7 Melt under Microgravity Conditions on the China Space Station

  • 期刊论文

  • 发表日期：

    2026年4月29日

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  • Huidong Li,
  • Ye Tao,
  • Chengcheng Cao,
  • Qiu Zhong,
  • Liping Yang,
  • Xiuhong Pan,
  • Zijun Xu,
  • Caiyun Luo,
  • Zhijie Jia

摘要

The growth of high-quality Na2Mo2O7 single crystals, a promising scintillator material, is critically dependent on the precise knowledge of their melt’s thermophysical properties. However, obtaining the intrinsic thermal conductivity of high-temperature melts is notoriously challenging on Earth due to buoyancy-driven convection. Here, we report the first direct measurement of the thermal conductivity of molten Na2Mo2O7, accomplished by employing a self-developed transient hot-wire system aboard the China Space Station. The microgravity environment effectively suppressed convection, enabling accurate measurement within the 750–900 °C range. Results reveal that the intrinsic thermal conductivity decreases monotonically from approximately 0.457 W/(m·K) to 0.416 W/(m·K) with increasing temperature, a trend attributed to the phonon-dominated conduction mechanism. In contrast, terrestrial measurements yielded systematically higher values (by 12.0–16.6%) due to convective contributions. This work not only fills a critical data gap for optimizing crystal growth but also establishes a robust methodology for probing the thermophysical properties of high-temperature melts in space.