Impact of isovalent and aliovalent substitution on the mechanical and thermal properties of Gd2Zr2O7

Abstract

In this study, a density functional theory method is employed to investigate the effects of isovalent and aliovalent substitution of Sm³⁺ on the phase stability, thermo-physical properties and electronic structure of Gd₂Zr₂O₇. It is shown that the isovalent substitution of Sm³⁺ for Gd³⁺ results in the formation of Gd₂Zr₂O₇-Sm₂Zr₂O₇ solid solution, which retains the pyrochlore structure and has slight effects on the elastic moduli, ductility, Debye temperature and band gap of Gd₂Zr₂O₇. As for the aliovalent substitution of Sm³⁺ for Zr⁴⁺ site, a pyrochlore-to-defect fluorite structural transition is induced, and the mechanical, thermal properties and electronic structures are influenced significantly. As compared with the Gd₂Zr₂O₇, the resulted Gd₂Sm_yZr_2-yO₇ compositions have much smaller elastic moduli, better ductility and smaller Debye temperature. Especially, an amount of electrons distribute on the fermi level and they are expected to have larger thermal conductivity than Gd₂Zr₂O₇. This study suggests an alternative way to engineer the thermo-physical properties of Gd₂Zr₂O₇ and will be beneficial for its applications under stress and high temperature.