Physical properties and radiation tolerance of high-entropy pyrochlores Gd2(Ti0.25Zr0.25Sn0.25Hf0.25)2O7 and individual pyrochlores Gd2X2O7 (X= Ti, Zr, Sn, Hf) from first principles calculations

Abstract

The physical properties of high-entropy ceramics (HEC) of Gd2(Ti0.25Zr0.25Sn0.25Hf0.25)2O7 and Gd2X2O7 (X = Ti, Zr, Sn, Hf) are investigated using first principles method. The structural properties, anti-site defect energetics, mechanical properties and electronic properties are compared. The lattice constant of HEC is within the range of its constituent pyrochlores, and the local lattice distortion presents in HEC. The cation anti-site defect is much easier to form in HEC than in pyrochlore, which implies that HEC can easily transfer to disordered fluorite structure and exhibit stronger radiation tolerance. The “high entropy” at B site of A2B2O7-type pyrochlore had no obvious effect on mechanical properties. The electronic properties of HEC and pyrochlore are characterized by projected density of states distribution and Bader charge, and the causes of HEC lattice distortion are investigated.