ZrB₂-20SiC (ZS20) composite and its derivatives doped with 5 vol% Sc₂O₃, Y₂O₃, and La₂O₃ were densified using hot press sintering to investigate the influence of rare earth oxides on their high temperature oxidation and ablation behavior. Isothermal oxidation testing at 1773 K indicate that rare earth oxides modification lowers activation energy and slightly accelerates weight gain during the initial phase. As oxidation progresses, the weight gain of ZS20 increases sharply. The sample doped with La₂O₃ (ZS20L5) exhibits the lowest oxidation weight gain, with a porosity of only 1.8 % after oxidation. Cyclic ablation tests at the middle-low temperature zones indicate that ZS20L5 exhibits the lowest linear and mass ablation rates. Thermodynamic analyses demonstrate that La₂O₃ preferentially reacts with SiO₂ to form La₂Si₂O₇, which demonstrates a more effective oxygen barrier property compared to ZrSiO₄. Additionally, La₂O₃ enhances the fluidity of the glass phase, effectively filling cracks, sealing pores, and blocking the penetration of oxygen.

Al₂O₃-based directionally solidified eutectic (DSE) ceramics are recognized as promising candidates for high-temperature structural materials in advanced aeroengines. Nevertheless, their corrosion resistance at elevated temperatures continues to pose a critical challenge, limiting broader application in hot-section components. This study investigates corrosion behavior of RE₃Al₅O₁₂ (REAG)/Al₂O₃ (RE = rare earth) DSE ceramics in water vapor atmosphere (90 H₂O(g) + 10 vol% air(g)) at 1500°C for durations up to 200 h, with focus on the influence of eutectic structure and RE elements in garnet phases via examining three samples (high-entropy (Y_0.2Gd_0.2Ho_0.2Er_0.2Yb_0.2)₃Al₅O₁₂ DSEs fabricated at 10 and 300 mm/h and YAG/Al₂O₃ DSE grown at 10 mm/h). The results indicate that REAG/Al₂O₃ DSE ceramics exhibit excellent water vapor corrosion resistance at 1500°C for up to 200 h, with mass loss values ranging from −0.00757 to −0.00708 mg·cm⁻²·mg⁻¹. During corrosion, Al₂O₃ phase acts as corrosion-susceptible component compared to REAG phase, with corrosion depth showing a nearly linear relationship with the average Al₂O₃ lamellar width. In addition, garnet phases experience slight grain growth, reducing the contact area between water vapor and Al₂O₃ phase; Gd demonstrates the slowest diffusion rate when compared to other RE elements. Despite these changes, all samples maintain their preferred crystallographic orientations, confirming the structural stability of REAG/Al₂O₃ DSEs under water vapor atmosphere at 1500°C.

Thermal protection coatings for aerospace applications require robust mechanical properties, exceptional thermal insulation, and high impact resistance to safeguard critical hot-section components and thereby extend their service life. Previous studies have confirmed that high-entropy titanate (La_0.3K_0.1Ca_0.2Sr_0.2Ba_0.2)TiO_3+δ (HE-LKTO) materials have excellent thermal protection properties and mechanical properties. To evaluate the viability of the HE-LKTO for Thermal protection coatings, a novel high-entropy titanate coating with a non-equimolar A-site composition was fabricated via atmospheric plasma spraying. The as-sprayed coatings subsequently underwent a comprehensive analysis of their microstructure and phase structure. Guided by the experimental results, the coating prepared under the optimized conditions was systematically investigated for its thermal protection performance via plasma flame thermal shock testing. The failure mechanism was revealed by analyzing the coating’s dynamic behavior under extreme heat flux. Results show that the HE-LKTO coating prepared at 36 kW exhibits the optimal microstructure: the sprayed particles achieve complete melting and effective spreading, resulting in the lowest surface roughness and porosity. In addition, HE-LKTO coating maintains structural integrity at ablation temperatures of 1400 ℃, exhibiting excellent high-temperature protection performance. At the extreme temperature of 1600 ℃, however, the coating began to spall as a result of accumulated thermal stress induced by the mismatched thermal expansion coefficients between the coating and substrate, as well as crack propagation along interlamellar boundaries and interface separation. This work not only validates the great potential of HE-LKTO as thermal protection coatings but also provides crucial insights into its failure mechanism, laying a foundation for future performance enhancement.

High-temperature corrosion caused by low-melting-point molten salts known as CMAS poses a critical challenge to hot-section components in gas turbine engines. The screening of CMAS corrosion-resistant RE₂SiO₅ ceramics is crucial for the development of environmental barrier coatings for SiC fiber reinforced SiC composites. Due to varying experimental methods, conditions, and CMAS corrosion evaluation approaches, there has been some controversy regarding the CMAS resistance of RE₂SiO₅ ceramics. To address this issue, we employed a highthroughput multilayer stacking method to eliminate external influences such as experimental conditions. The CMAS resistance of several rare earth silicate ceramics was investigated, which revealed the influence of rare earth elements on CMAS corrosion. It was found that the smaller the rare earth ionic radius, the less corrosion product formed. Additionally, Er₂SiO₅ exhibited the best CMAS resistance due to the shallowest penetration depth of CMAS. The results indicate that the evaluation of CMAS corrosion resistance of RE₂SiO₅ ceramics requires a comprehensive consideration of the formation ability of corrosion products, dissolution of RE₂SiO₅, and the penetration of CMAS.

With the advancement of modern aeroengines toward higher thrust-to-weight ratios and increased gas temperatures, the control of rotor-stator clearances has become a critical factor influencing engine performance and efficiency. Abradable seal coatings (ASCs), as an effective means of clearance control, have been widely applied to the inner casings of engines. Under high-temperature service conditions ($\ge {1300}^{\circ }\mathrm{C}$≥1300∘C), conventional metalbased ASCs are increasingly exhibiting service performance limitations due to their insufficient thermal stability. In contrast, ceramic-based abradable seal coatings, owing to their excellent high-temperature stability and low thermal conductivity, are considered promising candidates for next-generation high-temperature sealing materials. However, the design of such novel ASCs faces numerous key challenges, including crack propagation, the trade-off between abradability and erosion resistance, and coating failure mechanisms under extremely complex service environments. This review systematically summarizes the recent progress in high-temperature ceramic-based ASCs, with a focus on typical material systems, fabrication techniques, key structural design strategies, and their relationship with performance evolution. Comprehensive analysis reveals significant coupling and trade-offs among abradability, hardness, erosion resistance, thermal shock resistance, and corrosion resistance. Achieving balanced performance requires multiscale structural design and multifunctional synergistic optimization. Finally, this paper summarizes the main challenges currently faced in this field and emphasizes that future research should focus more on understanding the evolution of failure mechanisms under complex service environments and on the design and construction of integrated multifunctional coating architectures.

CrTaO₄ and CrNbO₄, rutile structured ternary scales formed on refractory high-entropy alloys (RHEAs), protect the RHEAs from oxidation and thermal attack. However, the Vickers hardness (12.20/10.20GPa for CrTaO₄ and CrNbO₄, respectively) is lower than that of YSZ (14 GPa), making them prone to erosion. In addition, further reduction of thermal conductivity (1.31/1.09 W⋅ m^-1⋅ K^-1 for CrTaO₄ and CrNbO₄, respectively) benefits to protect the substrate materials from thermal attack. As such, optimizing their properties is urgently needed. To enhance the mechanical properties and further reduce the thermal conductivity of rutile-type ternary oxides CrTaO₄ and CrNbO₄, herein we designed a CrTa_0.5Nb_0.5O₄ solid solution based on the mechanism of solid solution strengthening, and systematically investigated its phase composition, microstructure, mechanical and thermal properties. The HAADF and ABF-STEM analyses confirmed the rutile-structure of CrTa_0.5Nb_0.5O₄, while minor impurities of rutile-structured CrNbO₄ and CrO₂ were also identified. The elastic modulus, bulk modulus, and shear modulus of CrTa_0.5Nb_0.5O₄ are 201, 119, and 175 GPa, respectively. Notably, the mechanical properties of CrTa_0.5Nb_0.5O₄ have been significantly improved via solid solution strengthening, with the Vickers hardness of 13.01±0.2GPa, fracture toughness of 2.07±0.017MPa⋅m^1/2, and flexural strength of 201±12MPa. The measured melting point of CrTa_0.5Nb_0.5O₄ is 2073±20 K, with an average thermal expansion coefficient of (5.91±0.52)×10^-6 K^-1. The room-temperature thermal conductivity of CrTa_0.5Nb_0.5O₄ is 1.07 W⋅ m^-1⋅ K^-1, which decreases to 0.57 W⋅ m^-1⋅ K^-1 at 1473 K, being lower than most of the well-known thermal barrier coating materials. In terms of thermal expansion coefficient matching, CrTa_0.5Nb_0.5O₄ is a qualified thermal barrier material for refractory metals and their alloys and ultra-high temperature ceramics. Therefore, this study has not only successfully developed a thermal barrier coating material with excellent mechanical properties and low thermal conductivity, but also provided new ideas for the research and development of materials in high-temperature fields from the perspective of material design.

High-entropy ceramics (HECs) have attracted growing research attention since 2015, when the pioneering work on entropy-stabilized oxides was first reported. Derived from the definition of high-entropy alloys, HECs initially referred to disordered ceramic solid solutions comprising five or more principal elements in equimolar ratios occupying the same Wyckoff sites. The concept has rapidly evolved to encompass more complex systems with tunable element distributions across multiple crystallographic positions. Distinct from conventional ceramics, HECs are characterized by their unique chemical diversity and high configurational entropy, which contribute to enhanced structural stability and promising functional properties. Given the remarkable progress of HECs, this review systematically summarizes advancements over the past five years, including oxides (both simple and complex) and non-oxides (carbides, borides, and related compounds). Specifically, we focus on theoretical design principles for stability prediction and property optimization. We then examine the expanding compositional and structural space of emerging compounds and also discuss structure-property correlations and innovative processing methods. Furthermore, we provide a comprehensive overview of the most extensively investigated properties, including mechanical, thermal, electrical, catalytic, magnetic and dielectric characteristics. Looking forward, HECs hold great promise for various applications, and this review may provide some fundamental insights and practical design strategies for realizing their full potential.