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High-temperature CMAS corrosion has become a crucial factor inhibiting the further development of thermal barrier coatings (TBCs) because of the increasing service temperature of aero-engines. Herein, a novel mid-entropy rare-earth hafnate (Y0.3Gd0.3Yb0.4)4Hf3O12 (YGYbH) was prepared by ultrafast high-temperature sintering (UHS) technology, and its CMAS corrosion behavior and mechanism were investigated. During corrosion, the Ca2RE8(SiO4)6O2 apatite phase with a lower formation enthalpy and entropy-stabilized effect had a more intense tendency to be generated, which improves the density and stability of the reaction layer, hindering the further penetration of molten CMAS. Moreover, the significant lattice distortion caused by the rare-earth ions with different radii impeded the ionic diffusion, which delayed the CMAS corrosion reaction. In general, YGYbH, with excellent CMAS corrosion resistance, has the potential to serve as a next-generation TBC material. [ABSTRACT FROM AUTHOR]

High-temperature calcium-magnesium-alumina-silicate (CMAS) attack has become a fatal factor hindering the development of thermal barrier coatings (TBCs). In this study, a promising entropy-stabilized (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2) 2 Hf 2 O 7 (5LaH) hafnate was synthesized and prepared successfully, and then the CMAS corrosion behavior was investigated. During the corrosion process, the precipitation of the apatite phase causing the aggregation of Hf4+ promotes the formation of the (Hf, Si)O 2 phase to generate a dense structure layer, which has a great barrier effect on the penetration of CMAS melt, and apatite phase with the entropy effect proves the stability of the reaction layer. Moreover, molten CMAS is less inclined to wetting and spreading on 5LaH surfaces compared to YSZ, which is also beneficial to the CMAS corrosion resistance. In general, the 5LaH exhibits great anti-CMAS corrosion performance. [ABSTRACT FROM AUTHOR]

High-temperature molten calcium-magnesium-alumina-silicate (CMAS) corrosion has become a fatal factor for the failure of aero-engine thermal barrier coatings. In this study, a promising entropy-stabilized (Y 0.2 Dy 0.2 Er 0.2 Tm 0.2 Yb 0.2) 4 Hf 3 O 12 (5YH) hafnate was prepared by the emerging ultrafast high-temperature sintering (UHS), and its corrosion and wetting behavior of molten CMAS were investigated. For the corrosion mechanism, the precipitation of the high-entropy apatite phase promotes the formation of the HfO 2 phase, and it can improve the density and stability of the slow-growing reaction layer, hindering the further penetration of molten CMAS. At 1300 ℃, a reaction layer with a three-layered morphology is generated, resulting from the decreased viscosity of the molten CMAS. Moreover, computational analysis shows that molten CMAS on the 5YH surface has a larger contact angle (17°) than traditional YSZ (13°), and the spreading area is about 90 % of traditional YSZ, which benefits for its good CMAS corrosion resistance. [ABSTRACT FROM AUTHOR]

An entropy-stabilized rare earth hafnate (Y 0.2 Dy 0.2 Er 0.2 Tm 0.2 Yb 0.2) 4 Hf 3 O 12 (5RH) with defective fluorite structure was successfully prepared by the emerging ultrafast high-temperature sintering (UHS) in less than six minutes. The 5RH ceramic possessed a higher thermal expansion coefficient (11.23 ×10−6/K, 1500 °C) and extremely low thermal conductivity (0.94 W/(m·k), 1300 ℃) owing to the larger lattice distortion of high-entropy materials. After high-temperature annealing at 1500 ℃, the 5RH showed extremely sluggish grain growth characteristics and excellent high-temperature phase stability, mainly attributed to the non-equilibrium sintering characteristic of the UHS and the sluggish diffusion effect of high-entropy materials. Therefore, (Y 0.2 Dy 0.2 Er 0.2 Tm 0.2 Yb 0.2) 4 Hf 3 O 12 has excellent potential as a next-generation thermal barrier coating material to replace traditional Y 2 O 3 stabilized ZrO 2. Finally, using the UHS to prepare high-entropy ceramics provides a new technique for fast-sintering and developing next-generation thermal barrier coating materials. • High-entropy (Y 0.2 Dy 0.2 Er 0.2 Tm 0.2 Yb 0.2) 4 Hf 3 O 12 ceramic is designed and successfully prepared by the emerging UHS. • The solid-phase synthesis and sintering densification of high-entropy ceramic bulks are simultaneously achieved by the UHS in less than six minutes. • The high-entropy (Y 0.2 Dy 0.2 Er 0.2 Tm 0.2 Yb 0.2) 4 Hf 3 O 12 ceramic shows great potential as new-generation thermal barrier coating material. • The emerging UHS provides ideas for the fast-sintering of ceramic materials and development of new materials. [ABSTRACT FROM AUTHOR]