Mechanical properties, thermal conductivity and defect formation energies of samarium immobilization in Gd2Zr2O7: First-principles study and irradiation experiment

A density functional theory (DFT) study was employed to investigate the mechanical property, thermal conductivity, Debye temperature, electronic structure and defect chemistry of (Gd1-xSmx)2Zr2O7. All the (Gd1-xSmx)2Zr2O7 compounds exhibit an excellent structural and mechanical stability (Gd0.25Sm0.75)2Zr2O7 has the lowest Young's modulus of 213.7 GPa, the largest Possion's ratio of 0.292, the lowest Debye temperature of 491.8 K and the lowest thermal conductivity. The calculated thermal conductivities of (Gd1-xSmx)2Zr2O7 are 1.17-1.21 W/(m center dot K) by the Clark's model and 1.32-1.36 W/ (m center dot K) by the Cahall's model, respectively. The formation energies of O vacancies at 48f site are negative, which increase with the Sm content, however, the formation energies of O vacancies at 8b site are almost invariable. In addition, Sm partly occupying the Gd-site reduces distinctly the formation energies of defects such as A-site vacancies, cation antisite defects, anion Frenkel pairs of oxygen at 8b site and cation interstitials, which suggests that Sm-doped Gd2Zr2O7, especially equimolar GdSmZr2O7, has a better irradiation tolerance. After the 16 MeV Ta-ion irradiation at a fluence of 1 x 1014 or 2 x 1014 ions/cm2, the crystal structure of GdSmZr2O7 transforms from pyrochlore to a defect fluorite without obvious amor-phous phase.(c) 2022 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

Automated summary

A density functional theory (DFT) study was conducted to investigate various properties of (Gd1-xSmx)2Zr2O7, including mechanical stability, thermal conductivity, Debye temperature, electronic structure, and defect chemistry. The compounds exhibited excellent structural and mechanical stability, with (Gd0.25Sm0.75)2Zr2O7 showing the lowest Young's modulus, highest Possion's ratio, lowest Debye temperature, and lowest thermal conductivity. The study also examined the formation energies of various defects and observed that Sm-doped Gd2Zr2O7, especially GdSmZr2O7, exhibited improved irradiation tolerance. Furthermore, after ion irradiation, the crystal structure of GdSmZr2O7 transformed from pyrochlore to a defect fluorite without amorphous phase.