Thermochemical compatibility and microstructure evolution of (Yb_0.7Gd_0.3)₄Hf₃O₁₂/Yb₂SiO₅/Si multilayers for T/EBCs

In this study, the novel tri-layer (Yb_0.7Gd_0.3)₄Hf₃O₁₂/Yb₂SiO₅/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_0.7Gd_0.3)₄Hf₃O₁₂ 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 Yb₂SiO₅ coating prepared by PS-PVD had a lamellar structure with high crystallinity and low porosity. The (Yb_0.7Gd_0.3)₄Hf₃O₁₂ coating exhibited an adherent interface with the Yb₂SiO₅ coating after thermal aging at 1400°C for 100 h, with no interfacial pores or layer debonding, indicating superior thermochemical compatibility of the (Yb_0.7Gd_0.3)₄Hf₃O₁₂/Yb₂SiO₅ interface. Moreover, the (Yb_0.7Gd_0.3)₄Hf₃O₁₂ coating exhibited high resistance to sintering and great phase stability at high temperatures, making it a promising top coat material for T/EBCs.