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<p>In this work, five high-entropy rare earth phosphate and one single component rare earth phosphate (LuPO<sub>4</sub>) coupons were synthesized as novel environmental barrier coating (EBC) material candidates for silicon carbide ceramic matrix composites (SiC-CMCs). Their high temperature steam corrosion resistance was investigated at 1400 °C for 60 h in the presence of Al(OH)<sub>3</sub> and Si(OH)<sub>4</sub> contamination, with the focus on microstructural evolution, new phase formation, reaction layer thickness, and mass loss. LuPO<sub>4</sub> shows a larger mass loss than all the high entropy phosphates, and the formation of a ~ 8.7 µm thick reaction layer enriched with micro-sized voids and porosity up to 19%. In contrast, high entropy phosphates exhibit significantly enhanced steam corrosion resistance at high temperatures with a lower porosity in the surface alteration layer than LuPO<sub>4</sub>. Among them, (Sc<sub>0.2</sub>Lu<sub>0.2</sub>Yb<sub>0.2</sub>Y<sub>0.2</sub>Gd<sub>0.2</sub>)PO<sub>4</sub> and (Sc<sub>0.2</sub>Lu<sub>0.2</sub>Yb<sub>0.2</sub>Y<sub>0.2</sub>Sm<sub>0.2</sub>)PO<sub>4</sub> are the least corroded samples based on the microstructure alteration observed by scanning electron microscope (SEM). Following the water vapor test, all the rare earth phosphates show the formation of a microvoided reaction layer of new phases, including RE<sub>2</sub>O<sub>3</sub>, Al<sub>5</sub>RE<sub>3</sub>O<sub>12</sub>, AlPO<sub>4</sub>, and RE<sub>2</sub>SiO<sub>5</sub>. The enhanced corrosion resistance of the high entropy rare earth phosphates is ascribed to the enhanced stability of the crystal structure because of their compositional complexity and size disordering. All these results indicate that high entropy rare earth phosphates are promising candidates for EBC for SiC-CMCs.</p>

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High temperature steam corrosion of LuPO4 and high-entropy rare earth phosphates in the presence of Al(OH)3 and Si(OH)4 impurities

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年6月20日

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  • Bishnu Pada Majee,
  • Keith Bryce,
  • Liping Huang,
  • Jie Lian

摘要

In this work, five high-entropy rare earth phosphate and one single component rare earth phosphate (LuPO4) coupons were synthesized as novel environmental barrier coating (EBC) material candidates for silicon carbide ceramic matrix composites (SiC-CMCs). Their high temperature steam corrosion resistance was investigated at 1400 °C for 60 h in the presence of Al(OH)3 and Si(OH)4 contamination, with the focus on microstructural evolution, new phase formation, reaction layer thickness, and mass loss. LuPO4 shows a larger mass loss than all the high entropy phosphates, and the formation of a ~ 8.7 µm thick reaction layer enriched with micro-sized voids and porosity up to 19%. In contrast, high entropy phosphates exhibit significantly enhanced steam corrosion resistance at high temperatures with a lower porosity in the surface alteration layer than LuPO4. Among them, (Sc0.2Lu0.2Yb0.2Y0.2Gd0.2)PO4 and (Sc0.2Lu0.2Yb0.2Y0.2Sm0.2)PO4 are the least corroded samples based on the microstructure alteration observed by scanning electron microscope (SEM). Following the water vapor test, all the rare earth phosphates show the formation of a microvoided reaction layer of new phases, including RE2O3, Al5RE3O12, AlPO4, and RE2SiO5. The enhanced corrosion resistance of the high entropy rare earth phosphates is ascribed to the enhanced stability of the crystal structure because of their compositional complexity and size disordering. All these results indicate that high entropy rare earth phosphates are promising candidates for EBC for SiC-CMCs.