Preparation, thermophysical properties, and mechanical properties of high-entropy (La0.2Ho0.2Sm0.2Gd0.2M0.2)2Zr2O7 (M=Tb, Er, Yb, Lu) ceramics designed by thermal properties tailoring theory

The targeted design of composition and properties for high-entropy rare-earth zirconates (HE-RE 2 Zr 2 O 7 ) using thermal properties tailoring theory represents a research hotspot in the field of thermal barrier coatings. This work designed and synthesized a class of HE-RE 2 Zr 2 O 7 via solid-state reaction by adjusting the mass disorder, size disorder, and electronegativity, including (La 0.2 Ho 0.2 Sm 0.2 Gd 0.2 Tb 0.2 ) 2 Zr 2 O 7 (#Tb), (La 0.2 Ho 0.2 Sm 0.2 Gd 0.2 Er 0.2 ) 2 Zr 2 O 7 (#Er), (La 0.2 Ho 0.2 Sm 0.2 Gd 0.2 Yb 0.2 ) 2 Zr 2 O 7 (#Yb), (La 0.2 Ho 0.2 Sm 0.2 Gd 0.2 Lu 0.2 ) 2 Zr 2 O 7 (#Lu). The phase composition and crystal structure were analyzed using XRD, Raman spectroscopy, and TEM, and the thermophysical and mechanical properties were evaluated. The results demonstrate that as the size disorder increases, HE-RE 2 Zr 2 O 7 gradually transforms from a single-phase structure to a dual-phase structure coexisting with pyrochlore and fluorite. In terms of thermophysical properties, all materials exhibit low thermal conductivity and good correlation with both size disorder and mass disorder. Among them, #Lu demonstrates the most outstanding thermal insulation performance, which is attributed to its strong Umklapp scattering and point defect scattering. Additionally, under the combined effects of electronegativity, lattice energy, and size disorder, #Lu exhibits the highest thermal expansion coefficient. Importantly, doping with different rare-earth elements increases the material’s configurational entropy and degree of lattice distortion, optimizing the high-temperature phase stability and chemical compatibility from the kinetic perspective. In terms of mechanical properties, #Lu exhibits the lowest Young’s modulus, highest hardness, and fracture toughness, which is attributed to its high internal size disorder and lattice distortion. This work employs thermal properties tailoring theory to customize the composition of high-entropy RE 2 Zr 2 O 7 . It is essential for developing RE 2 Zr 2 O 7 thermal barrier coatings with tunable thermophysical properties.