Performance Evolution of Gd2O3-Yb2O3-Y2O3-ZrO2 (GYYZO) Thermal Barrier Coatings After Thermal Cycling

Ions of Gd3+ and Yb3+ have radii similar to those of Zr4+, enabling them to form limited solid solutions in the ZrO2 lattice through substitution. After solid solution formation, oxygen vacancy defects and complex defect aggregates are generated, which are crucial for stabilizing the high-temperature phase structure and reducing thermal conductivity. Therefore, in this study, 8 wt% Y2O3 and 5 wt% Yb2O3 were doped with 5 wt%, 10 wt%, and 15 wt% Gd2O3, respectively, to stabilize zirconia powders. GYYZO thermal barrier coatings (TBCs) were fabricated via atmospheric plasma spraying (APS). Subsequently, the GYYZO coatings with different Gd2O3 addition amounts were subjected to continuous thermal shock cycling at 1100 °C for 10, 30, 60, 90, and 150 cycles. The results indicate that the incorporation of Gd2O3, Yb2O3, and Y2O3 leads to the formation of stable tetragonal ZrO2 phase in the GYYZO coatings. Although increasing the Gd2O3 addition amount reduces the thermal conductivity of the coatings, excessive Gd2O3 addition causes coating spallation. The GYYZO coating with 10 wt% Gd2O3 exhibits the lowest thermal conductivity of 0.59 W/(m·K). Additionally, the GYYZO coating with 10 wt% Gd2O3 can withstand thermal cycling for 150 cycles, while the one with 5 wt% Gd2O3 can endure 90 of thermal cycles. In contrast, the 8YSZ coating cracks and spalls after 60 thermal cycles. These findings demonstrate that doping ZrO2 with Gd2O3, Yb2O3, and Y2O3 can enhance the thermal cycling resistance of the coatings and effectively reduce their thermal conductivity, but excessive Gd2O3 addition will decrease the coating adhesion strength.