YSZ/SiO ₂ composite coatings with spherical SiO ₂ microstructure for enhanced thermal insulation and long‐term durability

Abstract To address the challenges of thermal insulation and service lifetime in traditional yttria‐stabilized zirconia (YSZ) coatings, this study proposes a novel YSZ/SiO 2 composite coating design based on Mie‐scattering theory. The SiO 2 ‐embedded YSZ composite coating was successfully deposited by an optimized air plasma spraying process, enabling the construction of a tailored microstructural architecture. The spherical SiO 2 particles, possessing a lower refractive index, intensified Mie scattering within the coating and effectively suppressed radiative heat transport. The composite coating deposited via the optimized spraying process exhibited a significantly improved interfacial bonding strength of 38 MPa. Specifically, at 5 wt% SiO 2 , the composite coating showed the highest reflectivity in the 3–5 µm and achieved a minimum thermal conductivity of 1.27 W/(m·K). Long‐term oxidation at 1000°C revealed that moderate interfacial diffusion of Si in the bond‐coat region promoted the formation of Ni 2 SiO 4 , which strengthened the coating–substrate interface adhesion. The composite coating exhibited a 50% improvement in durability compared with the YSZ sample, extending the service life extended to 900 h. These findings highlight a promising strategy to concurrently enhance the thermal insulation efficiency and long‐term stability of YSZ‐based thermal barrier coatings under demanding service environments.