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 similar to 10.0 GPa, K-I similar to 2.50 MPa m(0.5), and E-0 similar to 220 GPa). (La1/3Eu1/3Gd1/3)(2)Zr2O7 medium-entropy ceramics with a larger delta size${\delta }_{size}$ (4.36%) present relatively high thermal expansion coefficients (10.93 x310(-6) K-1, 1200 degrees C) and low thermal conductivity (1.57-1.58 W/(m K), 100-500 degrees C). These results suggest that the prepared rare-earth-zirconate medium-entropy ceramics can be used as a new type of thermal insulation materials.