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<p>Refractory ceramic materials are critical for applications in extreme high-temperature environments. Refractory high-entropy ceramics belong to this class of materials and show great potential due to their remarkable combination of properties. Traditionally, increasing compositional complexity and chemical diversity of high-entropy ceramics whilst maintaining a stable single-phase solid solution has been a primary design strategy for developing new ceramics. Here, we unveil an alternative strategy based on deviation from conventional equimolar composition towards non-equimolar composition space, enabling tuning the metastability level of the supersaturated single-phase solid solution. By employing high-temperature micromechanical testing and post-mortem microstructural characterization of refractory metal-based high-entropy nitrides, we observed the activation of an additional strengthening mechanism upon spinodal decomposition of the metastable phase into coherent cubic-phase domains exhibiting compositional modulation. This process propels the yield strength of a non-equimolar nitride at 1000 °C to a staggering 6.9 GPa, that is 43% higher than the most robust equimolar nitride.</p>

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Unlocking ultrastrong high-temperature ceramics via non-equimolar refractory metal high-entropy nitrides

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月27日

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  • O. V. Pshyk,
  • A. Vasylenko,
  • P. Küttel,
  • B. Wicher,
  • P. Schweizer,
  • J. Michler,
  • T.E.J. Edwards

摘要

Refractory ceramic materials are critical for applications in extreme high-temperature environments. Refractory high-entropy ceramics belong to this class of materials and show great potential due to their remarkable combination of properties. Traditionally, increasing compositional complexity and chemical diversity of high-entropy ceramics whilst maintaining a stable single-phase solid solution has been a primary design strategy for developing new ceramics. Here, we unveil an alternative strategy based on deviation from conventional equimolar composition towards non-equimolar composition space, enabling tuning the metastability level of the supersaturated single-phase solid solution. By employing high-temperature micromechanical testing and post-mortem microstructural characterization of refractory metal-based high-entropy nitrides, we observed the activation of an additional strengthening mechanism upon spinodal decomposition of the metastable phase into coherent cubic-phase domains exhibiting compositional modulation. This process propels the yield strength of a non-equimolar nitride at 1000 °C to a staggering 6.9 GPa, that is 43% higher than the most robust equimolar nitride.