Fabrication and Properties of Magnetoplumbite-type Rare-Earth Hexaaluminate Thermal Barrier Coating Materials

doi:10.15541/jim20250386

Abstract

Abstract: Magnetoplumbite-type rare-earth hexaaluminate RMgAl₁₁O₁₉ (RMA, R = La, Pr, Nd, Sm, Gd) have emerged as promising candidates for next-generation thermal barrier coatings (TBCs) capable of operating at temperatures exceeding 1300 ℃, owing to their high melting points, low thermal conductivity, and remarkable sintering resistance. To elucidate the influence of rare-earth ion substitution on the structural and functional properties, a series of single rare-earth cation substituted RMA ceramics were synthesized via a solid-state reaction route and densified using spark plasma sintering (SPS). Their phase composition, microstructure, thermophysical, and infrared radiative properties were systematically characterized by different measurements. All samples crystallize in a hexagonal magnetoplumbite-type structure, with both lattice parameters and unit cell volumes exhibiting a gradual contraction as the rare-earth ionic radius decreases. The grain growth rate generally increases with a reduction in ionic radius. The thermal diffusivity and conductivity of RMA ceramics decrease with increasing temperature, reaching a minimum of 3.19-2.86 W/(m·K) in the temperature range of 25-1000 ℃. The average thermal expansion coefficients vary from 8.22×10^-6 to 8.70×10^-6 K^-1 between 200 ℃ and 1300 ℃, indicating comparable thermo-physical across different compositions. In contrast, notable differences appear in the 3-5 μm infrared band, where PrMA exhibits the highest average emissivity (0.746) and LaMA exhibits the lowest (0.493), reflecting the critical role of rare-earth cation electronic structure in radiative behavior. This work elucidates the coupled thermal-radiative modulation mechanism induced by rare-earth ion substitution in magnetoplumbite-type hexaaluminates, offering valuable insights for the design of high-temperature TBC materials that combine low thermal conductivity with high infrared radiative performance.

Key words: thermal barrier coatings, RMgAl₁₁O₁₉, grain growth rate, thermo-physical properties, infrared radiation properties

CLC Number:

TB306

XU Mingyi, XIONG Ying, WANG Bo, ZHANG Yixin, CHEN Wenbo, CAO Xueqiang. Fabrication and Properties of Magnetoplumbite-type Rare-Earth Hexaaluminate Thermal Barrier Coating Materials[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20250386.

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