热环境障涂层用(Nd0.2Sm0.2Gd0.2Yb0.2Y0.2)3NbO7氧化物热物理与力学性能

刘畅; 高雅; 张红松; 倪利伟; 张昊明; 陈晓鸽

doi:10.16490/j.cnki.issn.1001-3660.2025.18.018

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表面技术 ›› 2025, Vol. 54 ›› Issue (18) : 184-190. DOI: 10.16490/j.cnki.issn.1001-3660.2025.18.018

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热环境障涂层用(Nd_0.2Sm_0.2Gd_0.2Yb_0.2Y_0.2)₃NbO₇氧化物热物理与力学性能

刘畅, 高雅, 张红松^*, 倪利伟, 张昊明, 陈晓鸽

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Thermophysical and Mechanical Properties of (Nd_0.2Sm_0.2Gd_0.2Yb_0.2Y_0.2)₃ NbO₇ Oxides for Thermal/Environmental Barrier Coatings

LIU Chang, GAO Ya, ZHANG Hongsong^*, NI Liwei, ZHANG Haoming, CHEN Xiaoge

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摘要

目的为充分发挥稀土氧化物材料的优异性能,研究适用于热环境障涂层表面层的材料,制备了(Nd_0.2Sm_0.2Gd_0.2Yb_0.2Y_0.2)₃NbO₇氧化物高熵陶瓷。方法采用溶胶凝胶法和高温烧结技术制备了(Nd_0.2Sm_0.2Gd_0.2Yb_0.2Y_0.2)₃NbO₇高熵陶瓷,研究了其晶体结构、显微组织、元素构成、热物理与常温力学性能。结果该高熵陶瓷的XRD和Raman图谱表明其具有单一晶体结构;高熵化设计降低了陶瓷材料的室温及高温热导率,其在室温及1 000 ℃时的热导率分别是1.07 W/(m·K)和1.03 W/(m·K),涂层具有良好的隔热性能;高熵陶瓷在室温至1 200 ℃范围内具有良好的相稳定性能,其热膨胀系数为10.14×10^-6 K^-1,满足热障涂层对热膨胀性能的要求;该高熵陶瓷的常温杨氏弹性模量为208 GPa,显微硬度约为9.27 GPa,断裂韧性为1.67 MPa·m^1/2。结论采用溶胶凝胶法和高温固相烧结法,成功制备了(Nd_0.2Sm_0.2Gd_0.2Yb_0.2Y_0.2)₃NbO₇纳米粉体和致密块体,该高熵陶瓷纳米粉体及致密块体均具有单一的焦绿石晶体结构,相对致密度大于90%,元素分布均匀;由于多种稀土离子共掺杂引起的晶格畸变及质量波动,以及大量氧空位的引入,加剧了声子的散射程度,该高熵陶瓷具有较低的室温及高温热导率;稀土元素掺杂降低了金属离子与氧离子之间的电负性差值,使其具有相对较高的热膨胀系数,其杨氏弹性模量与YSZ相当,但显微硬度和断裂韧性偏低。

Abstract

To exploit the excellent properties of rare earth oxide materials and develop suitable materials for the surface layer of thermal/ environmental barrier coatings, the work aims to design and synthesize (Nd_0.2Sm_0.2Gd_0.2Yb_0.2Y_0.2)₃NbO₇ high-entropy oxides. The high-entropy oxide was prepared by Sol-Gel method and high-temperature sintering technology with Nd₂O₃, Sm₂O₃, Gd₂O₃, Yb₂O₃, Y₂O₃ and Nb₂Cl₅ as origin chemicals. The lattice-structure, microstructure, element composition, thermophysical and room-temperature mechanical properties of achieved high-entropy oxide were investigated. The XRD and Raman spectra of naono-powder confirmed the single crystal structure for this high-entropy ceramics, and the corresponding bulk sample was also confirmed for the single pyrochlore-type lattice through XRD and Raman analysis. The bulk sample featured the densified micro-structure and well-distributed elements. The relationship curve between the specific heat capacity and temperature of the high-entropy ceramics showed that they were basically proportional to each other. The value of specific heat capacity ranged from 0.372 5 J/(kg·℃) at room temperature to 0.477 96 J/(kg·℃) at 1 000 ℃. Thermal diffusivity of the high-entropy ceramics decreased with the increasing temperature, which was consistent with the phonon thermal conduction mechanism exhibited by most oxide materials. The thermal diffusivity ranged from 0.31 mm²/s at 1 000 ℃ to 0.42 mm²/s at room temperature. The high-entropy design effectively reduced both room-temperature and high-temperature thermal conductivity of the ceramic material, with measured values of 1.07 W/(m·K) at room temperature and 1.03 W/(m·K) at 1 000 ℃. High-entropy ceramics showed no phase transformation or lattice change when the temperature increased from room temperature to 1 200 ℃, demonstrating excellent phase stability, which was conducive to extending the service life of thermal barrier coatings. Thermal expansion coefficient of the high-entropy was 10.14×10^-5 K^-1, which met the thermal expansion requirements for thermal barrier coating applications. Mechanical property characterization revealed a Young's modulus of 208 GPa. The lower elastic modulus increased the strain limit, thereby extending the thermal cycling service life of the applied components. Meanwhile, the lower elastic modulus was conducive to slowing down the phonon propagation speed and enhancing the thermal insulation performance. The micro-hardness of high-entropy ceramics was approximately 9.27 GPa, and the fracture toughness was about 1.67 MPa·m¹/² at ambient conditions. The micro-hardness and fracture toughness will be improved by process optimization or element adjustment in the future. The results indicate that the obtained high-entropy oxides are of single pyrochlore-type lattice. Its relative-density is higher than 90%, exhibiting even-element distribution. Owing to the aggravated phonon scattering caused by lattice-distortion, mass variation and introduced oxygen-vocation from multi-type rare-earth cation doping, its thermal conductivity at room and high-temperature decreased. Because of decreased electro-negativity-difference value between metal cations and oxygen ions, its thermal expansion coefficient is higher than that of YSZ, which is disadvantageous to thermal/environmental barrier coatings. Its Young's modulus is in the same order with those of YSZ, while the micro-hardness and the fracture-toughness are low.

导出引用

刘畅, 高雅, 张红松, 倪利伟, 张昊明, 陈晓鸽. 热环境障涂层用(Nd_0.2Sm_0.2Gd_0.2Yb_0.2Y_0.2)₃NbO₇氧化物热物理与力学性能[J]. 表面技术. 2025, 54(18): 184-190 https://doi.org/10.16490/j.cnki.issn.1001-3660.2025.18.018

LIU Chang, GAO Ya, ZHANG Hongsong, NI Liwei, ZHANG Haoming, CHEN Xiaoge. Thermophysical and Mechanical Properties of (Nd_0.2Sm_0.2Gd_0.2Yb_0.2Y_0.2)₃ NbO₇ Oxides for Thermal/Environmental Barrier Coatings[J]. Surface Technology. 2025, 54(18): 184-190 https://doi.org/10.16490/j.cnki.issn.1001-3660.2025.18.018

中图分类号： TG174.4

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