Effects of Spray Distance on the Microstructure and Thermal Cycling Behavior Of PS-PVD (Gd <sub>0.9</sub>Yb <sub>0.1</sub>) <sub>2</sub>Zr <sub>2</sub>O <sub>7</sub>/YSZ <sup>2 Thermal Barrier Coatings</sup>

In this study, (Gd0.9Yb0.1)2Zr2O7 (GYbZ)/yttria-stabilized zirconia (YSZ) double-ceramic-layer (DCL) thermal barrier coatings (TBCs) were prepared by plasma spray–physical vapor deposition (PS-PVD). The microstructure, mechanical performance and thermal cycling behavior of coatings prepared with spraying distances of 600, 800 and 1000 mm were investigated. The GYbZ coating prepared with a spraying distance of 600 mm showed a closely packed columnar structure. However, the GYbZ coatings prepared with spraying distances of 800 and 1000 mm showed a quasi-columnar structure. The GYbZ coating prepared with a spraying distance of 800 mm has the thickest columnar crystals with obvious inter-columnar gaps. In addition, this coating exhibited excellent mechanical performance and the best thermal shock resistance. The primary failure patterns appearing during thermal cycling on the surface of TBCs can be classified into the following five types: caves, exfoliation, delamination cracks, spalled areas and radiate cracks. Furthermore, the failure behavior of these coatings in water-quenching tests is clarified.