Ultra-low thermal conductivity and enhanced mechanical properties of high-entropy perovskite ceramics

At present, the research on high-entropy perovskite materials mainly focuses on electrical properties. When they are employed in high-temperature and high-pressure environments, the stability of their working performance is extremely important, but the research on them is very limited. A novel entropy-stabilized ceramic system, denoted as Ba(Zr 0.2 Ti 0.2 Sn 0.2 Hf 0.2 X 0.2 )O 3 (X = Nb 5+ , Ta 5+ ), featuring a disordered perovskite structure, was synthesized. The high entropy ceramic, Ba(Zr 0.2 Ti 0.2 Sn 0.2 Hf 0.2 Ta 0.2 )O 3 (abbreviated as HEC-Ta), manifests a thermal expansion coefficient (9.00 × 10 −6 K −1 at 1400 °C). It exhibits exceptional thermal stability within the range of 30 to 1400 °C, coupled with low thermal conductivity (1.97 W m −1 K −1 at 1200 °C) and superior mechanical properties ( H v = 10.96 GPa, E = 178.28 GPa). These properties are ascribed to a high degree of lattice distortion arising from the stochastic distribution of different cations, along with the high entropy cocktail effect, leading to increased phonon scattering. This study thus presents a novel approach to develop a ceramic material devoid of rare earth elements, and can be enlightened for the application of perovskite materials in high temperature environments.