Microstructure and thermal properties of high-entropy RE3MO7-type ceramics with multiple cations at RE and M sites

Abstract

High-entropy RE3MO7-type ceramics with multiple cations at RE and M sites have been successfully fabricated via solid-state reaction method. The microstructure and thermal properties of two compositions, namely (Y1/3Yb1/3Er1/3)3 (Nb1/2Ta1/2)O7 and (Y1/3Yb1/3Er1/3)3(Nb1/3Ta1/3Mo1/3)O7, are studied. The XRD Rietveld refinement, transmission electron microscopy and scanning electron microscopy results demonstrate that the samples have pure disordered defective fluorite structure with highly homogeneous composition. These high entropy ceramics exhibit good thermal stability, high thermal expansion coefficients (11.1–11.5 × 10−6 K−1, 1000 °C), and low thermal conductivities (0.91–1.16 W m−1 K−1, 30–1000 °C), which make them promising for applications as thermal barrier coating materials.