Enhanced thermal radiation blocking of YSZ-LaMgAl₁₁O₁₉ thermal barrier coatings consisting of splat interfaces with different refractive indexes

The thermal sintering and infrared transparency of YSZ thermal barrier coatings (TBCs) greatly limit its thermal insulation and service lifetime. To address this, YSZ-LaMgAl₁₁O₁₉ (YSZ-LMA) composite TBCs consisting of YSZ/LMA splat interfaces aligned parallel to the coating surface are designed and prepared. The pinning effect of La³⁺ on YSZ splat boundary inhibits the healing of inter-splat pores, and the flake-like morphology of LMA allows coating to maintain micropores at high temperature, thereby enhancing its sintering resistance. The parallel YSZ/LMA interfaces with different refractive indexes form a multilayer structure aligned perpendicular to the coating surface which increase the multi-reflections of thermal radiation within the coating and improve the thermal radiation blocking. Consequently, YSZ-LMA TBCs show a higher thermal radiation reflectance and relatively lower thermal conductivity than YSZ TBCs after a heat treatment at 1300°C for 200 h, resulting in a reduction of simulated substrate temperature by up to 36.7 K.