Microstructural optimization of Gd₂O₃-Yb₂O₃-Y₂O₃ co-stabilized ZrO₂/YSZ coatings with enhanced thermal shock resistance

Yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are widely used in high-temperature applications, yet their thermal durability remains a critical limitation. To address this, double-ceramic-layer (DCL) TBCs have attracted growing attention due to their enhanced thermal performance. However, the key parameters influencing their thermal shock resistance are not yet fully understood. In this study, DCL TBCs composed of a Yb₂O₃-Y₂O₃ co-stabilized ZrO₂ (GYYZO) top layer and a Y₂O₃-stabilized ZrO₂ (YSZ) bottom layer were fabricated using atmospheric plasma spraying (APS). A series of coatings with varied porosities and thickness ratios were systematically prepared to evaluate their effects on thermal shock behavior. The results reveal that both excessively high or low porosity and imbalanced thickness ratios negatively impact the coating's performance. Specifically, coatings with a porosity in the range of 10–20% and a thickness ratio of 5:5 demonstrated the highest thermal shock resistance. This configuration provides an optimal balance between thermal insulation and mechanical integrity. The findings offer practical guidance for the structural design of advanced DCL TBC systems and contribute to the development of more durable coatings for high-temperature environments.