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_0.2Ti_0.2Sn_0.2Hf_0.2X_0.2)O₃ (X = Nb⁵⁺, Ta⁵⁺), featuring a disordered perovskite structure, was synthesized. The high entropy ceramic, Ba(Zr_0.2Ti_0.2Sn_0.2Hf_0.2Ta_0.2)O₃ (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.