Thermochemical compatibility and microstructure evolution of (Yb 0.7 Gd 0.3 ) 4 Hf 3 O 12 /Yb 2 SiO 5 /Si multilayers for T/EBCs

Abstract In this study, the novel tri‐layer (Yb 0.7 Gd 0.3 ) 4 Hf 3 O 12 /Yb 2 SiO 5 /Si thermal/environmental barrier coatings (T/EBCs) were prepared by plasma spray‐physical vapor deposition (PS‐PVD) and atmospheric plasma spray. The thermochemical compatibility, microstructure evolution, phase compositions, and mechanical properties of the novel T/EBCs were systematically investigated. The (Yb 0.7 Gd 0.3 ) 4 Hf 3 O 12 coating deposited by PS‐PVD exhibited a “quasi‐columnar” structure with a “feather‐like” microscopic morphology, with a nanohardness of ∼3.19 GPa and an elastic modulus of ∼43.98 GPa, while the Yb 2 SiO 5 coating prepared by PS‐PVD had a lamellar structure with high crystallinity and low porosity. The (Yb 0.7 Gd 0.3 ) 4 Hf 3 O 12 coating exhibited an adherent interface with the Yb 2 SiO 5 coating after thermal aging at 1400°C for 100 h, with no interfacial pores or layer debonding, indicating superior thermochemical compatibility of the (Yb 0.7 Gd 0.3 ) 4 Hf 3 O 12 /Yb 2 SiO 5 interface. Moreover, the (Yb 0.7 Gd 0.3 ) 4 Hf 3 O 12 coating exhibited high resistance to sintering and great phase stability at high temperatures, making it a promising top coat material for T/EBCs.