The lattice distortion, mechanical and thermodynamic properties of A(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3 (A = Sr, Ba) high-entropy perovskite with B-site disorder: First principles prediction

Abstract

High-entropy perovskite oxides are novel high-entropy ceramics developing recently. In this work, the local lattice distortion, mechanical and thermodynamic properties of perovskites A(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3 (A = Sr, Ba) are explored using the first principle investigation. The equilibrium lattice parameter and bulk moduli of high-entropy perovskites obtained by fitting approximately satisfy the rule of mixture of the components, while the entropy effect of component mixing is very small. The bond length distribution reveals the B-site disorder results in large local lattice distortion. The atomic displacement indicates larger average displacement of O atoms contributes mainly to the wider bond length distribution for most B-O bond. The distortion degree at B-site is naturally associated with A-site. The obtained elastic constants of high-entropy perovskites are also closed to the rule of mixing of the components. Compared with ternary SrTiO3 and BaTiO3 perovskites, B-site mixing for high-entropy perovskites enhances their toughness at expense of strength and stiffness, showing the elastic moduli can be modified and adjusted through multi-component design strategy. Relevant thermodynamic property reveals the B-site disorder is benefit to improve the resistance to softening and suppress volume expansion at high temperature. Electronic structures show the insulator–metal transition takes place, also uncover that the interaction of B-O bond is stronger.