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<p>A novel biphasic Dy<sub>2</sub>Hf<sub>2</sub>O<sub>7</sub>-HfO<sub>2</sub> composite was synthesized via a solid-state reaction route for potential thermal barrier coating (TBC) applications. X-ray diffraction confirmed that the reaction between Dy<sub>2</sub>O<sub>3</sub> and HfO<sub>2</sub> at 1500&#xa0;°C yields a dense composite comprising ∼81 wt% cubic pyrochlore Dy<sub>2</sub>Hf<sub>2</sub>O<sub>7</sub> and ∼19 wt% cubic fluorite HfO<sub>2</sub>. Microstructural analysis revealed a hierarchical architecture of nanoscale crystallites (25–34&#xa0;nm for Dy<sub>2</sub>Hf<sub>2</sub>O<sub>7</sub> and ~ 13&#xa0;nm for HfO<sub>2</sub>) agglomerated into faceted microparticles (~ 1.1&#xa0;μm). Williamson-Hall analysis indicated significant lattice strain within the Dy<sub>2</sub>Hf<sub>2</sub>O<sub>7</sub> phase due to its complex pyrochlore framework and cation-size mismatch, whereas HfO<sub>2</sub> remained nearly strain-free. The thermophysical properties of Dy<sub>2</sub>Hf<sub>2</sub>O<sub>7</sub>–HfO<sub>2</sub> composites were studied from room temperature to 1200&#xa0;°C. The thermal expansion coefficient increased from 7.6 × 10<sup>− 6</sup> K<sup>− 1</sup> to 9.2 × 10<sup>− 6</sup> K<sup>− 1</sup> between room temperature and 1200&#xa0;°C, while thermal diffusivity and conductivity decreased due to enhanced phonon–phonon scattering and interfacial disorder. The specific heat capacity rose from 0.35 to 0.50 Jg<sup>−1</sup>K<sup>− 1</sup>, consistent with Debye behavior approaching the Dulong-Petit limit. The composite’s low thermal conductivity (~ 1.3&#xa0;W/mK at 1200&#xa0;°C) and moderate thermal expansion, indicating its excellent thermal stability and suitability for high-temperature insulation and thermal barrier coating applications.</p>

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Microstructural and thermophysical properties of Dy2Hf2O7-HfO2 composite for thermal barrier coating applications

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月18日

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  • Ashwini Kumar,
  • Yong Gong,
  • Jin Cui,
  • Fujun Qiu,
  • Yong Zhang,
  • Xingyu Pu,
  • Poorva Sharma

摘要

A novel biphasic Dy2Hf2O7-HfO2 composite was synthesized via a solid-state reaction route for potential thermal barrier coating (TBC) applications. X-ray diffraction confirmed that the reaction between Dy2O3 and HfO2 at 1500 °C yields a dense composite comprising ∼81 wt% cubic pyrochlore Dy2Hf2O7 and ∼19 wt% cubic fluorite HfO2. Microstructural analysis revealed a hierarchical architecture of nanoscale crystallites (25–34 nm for Dy2Hf2O7 and ~ 13 nm for HfO2) agglomerated into faceted microparticles (~ 1.1 μm). Williamson-Hall analysis indicated significant lattice strain within the Dy2Hf2O7 phase due to its complex pyrochlore framework and cation-size mismatch, whereas HfO2 remained nearly strain-free. The thermophysical properties of Dy2Hf2O7–HfO2 composites were studied from room temperature to 1200 °C. The thermal expansion coefficient increased from 7.6 × 10− 6 K− 1 to 9.2 × 10− 6 K− 1 between room temperature and 1200 °C, while thermal diffusivity and conductivity decreased due to enhanced phonon–phonon scattering and interfacial disorder. The specific heat capacity rose from 0.35 to 0.50 Jg−1K− 1, consistent with Debye behavior approaching the Dulong-Petit limit. The composite’s low thermal conductivity (~ 1.3 W/mK at 1200 °C) and moderate thermal expansion, indicating its excellent thermal stability and suitability for high-temperature insulation and thermal barrier coating applications.