Influence of size disorder parameter on the thermophysical properties of rare-earth-zirconate medium-entropy ceramics

Inspired by the concept of entropy stabilization, a series of rare-earth-zirconate medium-entropy ceramics were designed. The influence of size disorder parameter on the mechanical and thermophysical properties of rare-earth-zirconate medium-entropy ceramics was investigated. The results show that the prepared rare-earth-zirconate medium-entropy ceramics exhibit single pyrochlore structure, and the lattice constant is linearly related to the average doped rare-earth ionic radius. The scanning electron microscope-energy-dispersive spectroscopy results indicate the uniform distribution of doped rare-earth elements. The rare-earth-zirconate medium-entropy ceramics have relative density above 98.1% with high mechanical properties (H_V ∼ 10.0 GPa, K_Ⅰ ∼ 2.50 MPa m^0.5, and E₀ ∼ 220 GPa). (La_1/3Eu_1/3Gd_1/3)₂Zr₂O₇ medium-entropy ceramics with a larger (Formula presented.) (4.36%) present relatively high thermal expansion coefficients (10.93 ×310⁻⁶ K⁻¹, 1200°C) and low thermal conductivity (1.57–1.58 W/(m K), 100–500°C). These results suggest that the prepared rare-earth-zirconate medium-entropy ceramics can be used as a new type of thermal insulation materials.