Role of Powder Mixing Ratio in the Aerosol Deposition of YSZ–Al₂O₃ Composite Coatings

Aerosol deposition (AD) is a solid-state coating technique capable of producing dense ceramic films at room temperature through the high-velocity impact of fine particles. Our Previous work demonstrated that YSZ–Al₂O₃ composite coatings can be produced by aerosol deposition using ball-milled α-Al₂O₃ powders in YSZ media. However, the role of powder composition in controlling deposition efficiency and coating densification remains poorly understood. In this study, composite coatings were fabricated using mixed powders of α-Al₂O₃ and 3 mol% yttria-stabilized zirconia (3YSZ) with different mixing ratios via AD. The results indicate that powder composition strongly influences coating formation. Increasing the α-Al₂O₃ fraction in the mixed feedstock significantly improves deposition efficiency and promotes the formation of denser coatings with reduced porosity. SEM observations reveal that coatings produced with higher Al₂O₃ content exhibit a more compact microstructure and fewer voids compared with mixtures containing higher fractions of YSZ nanoparticles. These findings suggest that micron-scale Al₂O₃ particles play a dominant role in the impact fragmentation and consolidation process, enhancing particle packing and coating densification in composite AD coatings.