Thermal barrier coatings are indispensable shields that protect the hot-end components of gas turbines and aircraft engines from extreme temperatures. Current industry-standard YSZ coatings face several critical limitations: an unstoppable phase transition that restricts operating temperatures below 1200 °C, dramatically rising thermal conductivity due to thermal radiation above 900 °C, severe corrosion by CaO–MgO–Al2O3–SiO2 (CMAS) melts, and vulnerability to moisture degradation. These combined deficiencies have driven urgent demand for next-generation TBC materials capable of sustained service at 1200–1500 °C.
High-entropy ceramics (HECs) have emerged as promising candidates to address these challenges. HECs contain more than four elements occupying one or more lattice sites, forming single-phase materials that benefit from four synergistic effects: the high-entropy effect enhances phase stability; the sluggish diffusion effect inhibits secondary-phase formation; severe lattice distortion improves mechanical properties; and the cocktail effect generates unexpected performance enhancements. Now, a research team led by Prof. Jing Feng and Dr. Lin Chen from the Faculty of Materials Science and Engineering at Kunming University of Science and Technology has designed and evaluated novel tantalate HECs coatings as next-generation TBCs with working temperatures reaching 1500 °C.
The team published their work in Journal of Advanced Ceramics on February 8, 2026.
The tantalate HECs coatings were synthesized via air plasma spraying (APS) onto Ni-based alloy substrates. During APS, the extremely high processing temperatures promoted the complete dissolution of Yb3+, Y3+, Ta5+, and Nb5+ cations into ZrO2 lattices, yielding single-phase fluorite ceramic coatings approximately 150 μm thick with a bond coat of 120 μm. The coatings were then subjected to three rigorous thermal measurements: thermal shock at 1500 °C for 614 cycles, thermal fatigue at 1150 °C for 12,830 cycles, and isothermal annealing at 1100 °C for 384 hours. Remarkably, the coatings maintained excellent structural integrity and a stable fluorite crystal structure throughout all tests.
"The thermal stress caused by temperature gradients and differences in thermal expansion coefficients and mechanical properties between ceramic coatings and the bond coat is the dominant factor for coating failure during thermal shock at 1500 °C. In contrast, during thermal fatigue at 1150 °C, the progressive thickening of the thermally grown oxide layer drives crack formation once the TGO thickness-to-undulation radius ratio exceeds 0.32," said Prof. Jing Feng, whose research focuses on advanced ceramics for extreme-temperature applications.
The study revealed two distinct failure mechanisms. During thermal shock, enormous thermal stress arising from the 350 °C temperature gradient between the coating surface and the bond coat, combined with mismatches in thermal expansion coefficients and modulus, generated interfacial transverse cracks that coalesced and led to coating spalling. During thermal fatigue, cumulative oxidation of the bond coat produced NiCr2O4 thermally grown oxides (TGO); when the TGO thickness exceeded the critical ratio relative to its undulation radius, the driving force surpassed the fracture resistance, triggering interfacial cracking. Additionally, sintering-induced recrystallization and increased coating stiffness contributed to surficial spalling.
"The high working temperatures, excellent thermal insulation performance, and long service life synergistically validate that our designed tantalate HECs can be further studied and used as next-generation high-performance oxide TBCs. These findings also provide critical guidance for the design and optimization of advanced coating systems," said Dr. Lin Chen, co-corresponding author of the study.
Future research will focus on enhancing the oxidation and ablation resistance of tantalate HECs coatings and evaluating their performance under real engine operating conditions, to further advance their deployment in next-generation aerospace propulsion systems.
Other contributors include Jiankun Wang, Luyang Zhang, Hao Xu, and Qinglin Zhou, all from the Faculty of Materials Science and Engineering at Kunming University of Science and Technology, China.
About Author
Lin Chen is a Distinguished Professor at Kunming University of Science and Technology. His research focuses on ultra-high temperature thermal protective coating materials. Prof. Chen has received the First Prize of the China Rare Earth Science and Technology Award, among other honors. He has published over 90 papers in leading journals including Prog. Mater. Sci., Adv. Mater., Acta Mater., and J. Adv. Ceram., with over 2,900 citations and an H-index of 30.
Jing Feng is a Professor, Doctoral Supervisor, and Dean of the Faculty of Materials Science and Engineering at Kunming University of Science and Technology. He is a recipient of the National Overseas High-Level Talent Program. Prof. Feng has achieved significant breakthroughs in theoretical design and high-temperature phase transition mechanisms, publishing over 230 papers in journals such as Prog. Mater. Sci., Nat. Commun., Acta Mater., and Phys. Rev. B, with over 18,000 citations and an H-index of 68. He also serves as Guest Associate Editor or Editorial Board Member for 10 SCI-indexed journals and holds over 80 international and national invention patents.
Funding
This work was supported by the National Natural Science Foundation of China (Nos. 52502065 and 52562006), Yunnan Major Scientific and Technological Projects (No. 202302AG050010), Academician (Expert) Workstation of Yunnan Province Program (No. 202305AF150005), Yunnan Province Innovation Team (No. 202305AS350018), and Research Innovation Cultivation Project of Yunnan Province (No. FWCY-BSPY2024051).
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
