Prediction of lattice distortion and mechanical behavior of tetragonal phase (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3 high-entropy perovskite with A-site disorder from first-principles calculations

Abstract

High-entropy perovskite ceramics have drawn widespread attention as their excellent physical properties. Herein, the high-entropy (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3 (BNBSCT) perovskite is selected as case study. The distorted structure and mechanical behavior as well as the effect of pressure are comprehensively studied through implementing first-principles calculations in conjunction with special quasi-random structure. The results reveal the atomic random distribution and size different cause serious lattice distortion within the BNBSCT structure, and the pseudo-intralayer distortion is significantly smaller than the interlayer distortion. Further studies of the mechanical properties indicate that the high-entropy BNBSCT perovskite is mechanical stable, especially larger elastic parameters imply the larger resistance against elastic deformation in comparison with Bi0.5Na0.5TiO3. Compared to the rule of mixture, the higher resistance to volume deformation and crack propagation of BNBSCT suggests the strengthening of high-entropy perovskite presumably due to lattice distortion in structure. Increasing pressure leads to decrease in lattice parameter and volume of structure, then increases the degree of lattice distortion, elastic constants and elastic moduli, as well the degree of lattice distortion. Moreover, the ductility and fracture toughness are also enhanced, though the elastic anisotropy is slightly larger. This work provides a new insight into the high-entropy perovskite under high pressure, which will contribute to the further research and application of high-entropy materials.