Thermal barrier coatings is a critical part in thermal protection system (TPS) of the aero engine hot-end component. Recent studies reveal that entropy-stabilized high-entropy oxide A6B2O17 (A= Hf, Zr; B= Ta, Nb) superstructures—exhibiting 4.50R J·mol-1·K-1 configurational entropy from cation disorder — demonstrate exceptional high-temperature stability (to 2250℃, favorable thermal expansion (10.9×10-6 ℃-1 at 1200℃, low thermal conductivity (1.0 W·m-1·K-1 at 1000℃, and high temperature chemical stability. Zr6Ta2O17 coating shows superior fracture toughness versus YSZ (3.8 vs. ~2.7 MPa·m1/2) and withstands 2000 thermal cycles at 1150℃. Combined with outstanding CMAS corrosion resistance in bulk and Na2SO4-V2O5 salt resistance in coating, this system emerges as a promising next-generation TBC candidate.
Recently, a team of material scientists led by Li Yang from Xidian University, China reported the mechanical and corrosion mechanisms of eutectic Zr-Ta-O core-shell/YSZ TBC by in-situ TEM and thermal shock test under CMAS corrosion.
This study presents a novel double-layered thermal barrier coating (TBC) system designed to enhance the protection of hot-section components in extreme environments. The system, fabricated using atmospheric plasma spraying (APS), features a unique eutectic Zr-Ta-O core-shell structured top layer applied over a conventional yttria-stabilized zirconia underlayer. The research focuses on evaluating this new architecture's mechanical properties and, critically, its resistance to degradation from calcium-magnesium-aluminosilicate (CMAS) corrosion, a major cause of TBC failure.
A key finding of the investigation is the exceptional mechanical performance of the eutectic ZTO top layer. In-situ mechanical testing revealed outstanding plastic deformability, with the material achieving a compressive strain exceeding 30%, alongside a remarkably high yield strength of up to 4.5 GPa. These properties are attributed to the unique eutectic microstructure, which provides a combination of strength and flexibility not typically found in conventional ceramic TBCs.
The study then rigorously tested the system's resistance to CMAS attack, a molten silicate deposit that infiltrates TBCs, leading to accelerated degradation and spallation. The results demonstrate that the dense ZTO top layer acts as a highly effective barrier against CMAS infiltration. This sealing capability is facilitated by eutectic solidification-induced densification, which physically blocks the molten corrosive from reaching the underlying YSZ substrate. Furthermore, the ZTO layer functions as a "sacrificial" protective element. Upon CMAS attack, phase transformations and a mismatch in thermal expansion between the corrosion products and the ZTO layer induce significant localized strain. This strain triggers the spallation, or flaking off, of the corrosive layer, effectively removing the damaging material and protecting the more vulnerable YSZ underlayer from direct attack.
To understand the underlying mechanics of failure, the researchers employed finite element simulations. These simulations quantitatively mapped the distribution of interfacial stress fields that govern crack propagation within the top layer during CMAS exposure. This modeling provides crucial insights into how the material's structure responds to corrosive stress, validating the observed experimental results. In conclusion, this study introduces a promising new design paradigm for CMAS-resistant TBCs. The combination of a mechanically robust, deformable eutectic ZTO top layer with a traditional YSZ underlayer creates a system with dual functionality: it effectively blocks CMAS infiltration while also sacrificially spalling away corrosive products to protect the underlying structure. This innovative architecture offers significant potential for extending the lifespan of components in high-temperature applications, such as gas turbine engines, by providing superior resistance to one of the most challenging forms of environmental degradation.
The furnace holding acts as an accelerated corrosion test that often causes over-oxidation, demanding higher bond coat and substrate treatment requirements. Current limitations arise from TGO-induced delamination at the bond coat, not the sacrificial mechanism itself. Bond coats require sufficient Al to form protective α-Al2O3 scales during initial oxidation, limiting TGO thickness and reducing in-plane stresses—unlike the chromia or spinel structures observed here. Future efforts should: (i) develop TGO-resistant bond coats (e.g., Pt-diffusion modified NiAl) compatible with ZTO/8YSZ; (ii) optimize spallation kinetics via shell thickness control to synchronize with CMAS attack rates; (iii) implement laser-assisted recoating for sacrificial layer renewal
The team published their work in Journal of Advanced Ceramics on April 14, 2026.
Other contributors include Jun-Hui Luo, Gang Yan, Guang-Nan Xu, Chang-Xing Zhang, Ke Cao, Jun-Kai Liu, Yi-Chun Zhou from the School of Advanced Materials and Nanotechnology, Xidian University, China.
About Author
Professor Yang Li, doctoral supervisor, currently serves as the executive dean of the School of Advanced Materials and Nanotechnology at Xidian University. She also holds positions such as Vice Chair of the Physical Mechanics Committee of the Chinese Society of Mechanics. Her primary research focus lies in the study of high-temperature and ultra-high-temperature coatings for aerospace applications and their mechanical behaviors. Her scholarly contributions include the publication of two seminal monographs: "Thermal Barrier Coatings: Failure Theory and Evaluation Technology" and "The Macro- and Micromechanical Properties." She has authored over 150 peer-reviewed articles in the fields of solid mechanics and materials science. Her innovative work has been recognized with two U.S. patents, one Russian patent, and more than 50 Chinese national patents. Her exceptional contributions to the field have earned her the First Prize of the Natural Science Award of Hunan Province and the First Prize of the Natural Science Award of Shaanxi Province.
Funding
This work was supported by the National Natural Science Foundation of China (Nos. 92371204, 12202330, 12502208 (PI: Qian-Qian Zhou), and U2341257), the National Science and Technology Major Project (No. J2022-V-0003-0029), the Fundamental Research Funds for the Central Universities and the Innovation Fund of Xidian University (YJSJ25017)
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen . JAC's 2024 IF is 16.6, ranking in Top 1 (1/34, Q1) among all journals in "Materials Science, Ceramics" category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
