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(Zr0.2Ti0.2Sn0.2Hf0.2X0.2)O3 (X = Nb5+, Ta5+), featuring a disordered perovskite structure, was synthesized. The high entropy ceramic, Ba(Zr0.2Ti0.2Sn0.2Hf0.2Ta0.2)O3 (abbreviated as HEC-Ta), manifests a thermal expansion coefficient (9.00 x 10-6 K-1 at 1400 degrees C). It exhibits exceptional thermal stability within the range of 30 to 1400 degrees C, coupled with low thermal conductivity (1.97 W m-1 K-1 at 1200 degrees C) and superior mechanical properties (Hv = 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. A novel entropy-stabilized ceramic system featuring a disordered perovskite structure manifests low thermal conductivity and superior mechanical properties.