Ta_1−xHf_xC_y ternary ceramics are highly valued in hypersonic vehicles, and a precise composition design is promising to simultaneously reduce their intrinsic brittleness and enhance their protective capability during oxidation. Herein, the composition-dependent mechanical properties and oxidation behaviors of Ta_1−xHf_xC_y ternary ceramics over a broad composition range (x = 0.22 to 0.78, y = 0.66 to 1.00) are efficiently investigated through combinatorial and high-throughput (CHT) experimentation to pave the way for targeted development of novel carbide candidates. Evolution trends in hardness and modulus reveal that the composition range with x = 0.22 to 0.60 and y = 0.80 to 1.00 is promising to reach an optimal balance between hardness and toughness, which results from competing effects between solid solution strengthening and bonding characteristic transition. High-throughput oxidation elucidates the phase constitution and compactness of oxidation products with various Ta/Hf distributions and temperatures. The accurate compositional range for the formation of a single-phase dense Hf–Ta–O compound layer shifts to a Ta-rich region (x = 0.50 to 0.60) due to the preferential formation of Ta-doped HfO₂ and the structural characteristics of Hf–Ta–O compounds that accommodate compositional deviations. Regarding the broad compositional space of Ta_1−xHf_xC_y, the effects of composition on both mechanical properties and oxidation behavior are systematically investigated, providing fundamental design guidelines and an optimal composition range that holds significant promise for application in subsequent research.

Environmental barrier coatings (EBCs) with thermomechanical robustness against calcium–magnesium–aluminum–silicate (CMAS) deposits are in high demand. The aim of this work was to clarify the influence of Sc³⁺ on the crystallization behavior of Yb-based coatings against CMAS deposits. The reaction products of solid solutions with compositions traversing the Sc₂O₃–Yb₂O₃ system indicate that Sc³⁺ tends to form [BO₆] coordination polyhedra in the crystal structure to promote the formation of garnet and diopside, while Yb³⁺ occupies 7-, 8-, and 9-coordinate sites to crystallize apatite and silicocarnotite. The transformation of crystalline products from apatite/silicocarnotite to garnet/diopside greatly improves the efficiency of CMAS melt consumption and facilitates the prevention of its further penetration and corrosion. Based on the commonality of cation occupancy in crystallography, an A(CaO+YbO_1.5)–B(ScO_1.5+MgO+AlO_1.5)–T(SiO₂) pseudoternary phase diagram is established, which has great potential for describing phase equilibrium in coating-deposit systems and can provide guidance for the compositional design of corrosion-resistant coatings.

Model composites consisting of SiC fiber and Yb₂SiO₅ were processed by the spark plasma sintering (SPS) method. The mechanical compatibility and chemical stability between Yb₂SiO₅ and SiC fiber were studied to evaluate the potential application of Yb monosilicate as the interphase of silicon carbide fiber reinforced silicon carbide ceramic matrix composite (SiC_f/SiC CMC). Two kinds of interfaces, namely mechanical and chemical bonding interfaces, were achieved by adjusting sintering temperature. SiC_f/Yb₂SiO₅ interfaces prepared at 1450 and 1500 ℃ exhibit high interface strength and debond energy, which do not satisfy the crack deflection criteria based on He–Hutchison diagram. Raman spectrum analyzation indicates that the thermal expansion mismatch between Yb₂SiO₅ and SiC contributes to high compressive thermal stress at interface, and leads to high interfacial parameters. Amorphous layer at interface in model composite sintered at 1550 ℃ is related to the diffusion promoted by high temperature and DC electric filed during SPS. It is inspired that the interfacial parameters could be adjusted by introducing Yb₂Si₂O₇–Yb₂SiO₅ interphase with controlled composition to optimize the mechanical fuse mechanism in SiC_f/SiC CMC.