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<p>High-entropy oxides used as thermal barrier coating materials have attracted considerable attention from scientific communities owing to their unique properties, such as low thermal conductivity and good stability at high temperatures. In this study, a new (La<sub>0.2</sub>Gd<sub>0.2</sub>Zr<sub>0.2</sub>Ce<sub>0.2</sub>Ho<sub>0.2</sub>)O<sub>2-δ</sub> ((LGZCH)O) fluorite-structured high-entropy oxide was successfully synthesized through a solid-state reaction at 1400&#xa0;°C. The resulting material demonstrated good phase stability after sintering at high temperatures. The microstructure, microscopic morphology, ionic valence, compositional distribution, optical properties, thermal conductivity, thermal expansion properties, and mechanical properties of (LGZCH)O were investigated. X-ray diffraction results showed that the (LGZCH)O fluorite-structured high-entropy oxide exhibited good stability during sintering at different temperatures with an optimum sintering temperature of 1580&#xa0;°C. Ce<sup>4+</sup> converted to Ce<sup>3+</sup> at high temperatures. Scanning electron microscopy results showed that the material had a high porosity of approximately 28.9% after sintering at 1580&#xa0;°C. (LGZCH)O had a higher infrared radiation emissivity of 82.2%-87.6% in the range of 2.5-6.0&#xa0;μm indicating that it had better thermal radiation shielding performance. After porosity modification, the thermal conductivity ranged from 1.27 to 1.00&#xa0;W&#xa0;m<sup>−1</sup>&#xa0;K&#xa0;<sup>−1</sup> from room temperature to 1000&#xa0;°C, which is considerably lower than that of yttria-stabilized zirconia. Additionally, (LGZCH)O exhibited low coefficients of thermal expansion measuring 9.65 × 10<sup>−6</sup>&#xa0;K<sup>−1</sup> and 10.13 × 10<sup>−6</sup>&#xa0;K<sup>−1</sup> at 1000 and 1200&#xa0;°C, respectively. The hardness and Young’s modulus of the bulk (LGZCH)O measured via nanoindentation tests were 8.86&#xa0;GPa and 153.98&#xa0;GPa, respectively, which are marginally inferior to those of YSZ. Therefore, (LGZCH)O can be considered a promising candidate material for thermal barrier coatings.</p>

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Investigation of (La0.2Gd0.2Zr0.2Ce0.2Ho0.2)O2-δ Fluorite-Structured High-Entropy Oxide as a Promising Thermal Barrier Coating Material

  • 期刊论文

  • 发表日期：

    2025年3月25日

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  • Dongbo Zhang,
  • Xinyue Tang,
  • Ning Wang,
  • Mingwei Xiao,
  • Jiangrong Yan,
  • Yongsheng Zhang

摘要

High-entropy oxides used as thermal barrier coating materials have attracted considerable attention from scientific communities owing to their unique properties, such as low thermal conductivity and good stability at high temperatures. In this study, a new (La0.2Gd0.2Zr0.2Ce0.2Ho0.2)O2-δ ((LGZCH)O) fluorite-structured high-entropy oxide was successfully synthesized through a solid-state reaction at 1400 °C. The resulting material demonstrated good phase stability after sintering at high temperatures. The microstructure, microscopic morphology, ionic valence, compositional distribution, optical properties, thermal conductivity, thermal expansion properties, and mechanical properties of (LGZCH)O were investigated. X-ray diffraction results showed that the (LGZCH)O fluorite-structured high-entropy oxide exhibited good stability during sintering at different temperatures with an optimum sintering temperature of 1580 °C. Ce4+ converted to Ce3+ at high temperatures. Scanning electron microscopy results showed that the material had a high porosity of approximately 28.9% after sintering at 1580 °C. (LGZCH)O had a higher infrared radiation emissivity of 82.2%-87.6% in the range of 2.5-6.0 μm indicating that it had better thermal radiation shielding performance. After porosity modification, the thermal conductivity ranged from 1.27 to 1.00 W m−1 K −1 from room temperature to 1000 °C, which is considerably lower than that of yttria-stabilized zirconia. Additionally, (LGZCH)O exhibited low coefficients of thermal expansion measuring 9.65 × 10−6 K−1 and 10.13 × 10−6 K−1 at 1000 and 1200 °C, respectively. The hardness and Young’s modulus of the bulk (LGZCH)O measured via nanoindentation tests were 8.86 GPa and 153.98 GPa, respectively, which are marginally inferior to those of YSZ. Therefore, (LGZCH)O can be considered a promising candidate material for thermal barrier coatings.