磁铅石型稀土六铝酸盐热障涂层材料的制备与性能OA

Magnetoplumbite-type rare-earth hexaaluminates RMgAl11O19(RMA,R=La,Pr,Nd,Sm,Gd)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.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 2.86-3.19 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 properties 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.