Effects of Nd doping on the mechanical properties and electronic structures of Gd₂Zr₂O₇: a first-principles-based study

Doping of cations in A₂B₂O₇-type pyrochlores, either on A or B site, can modify the physical properties of compounds significantly. In this work, the structural, thermo-mechanical and electronic properties of Nd-doped Gd₂Zr₂O₇ pyrochlores (Gd_2−yNd_yZr₂O₇ and Gd₂Zr_2−yNd_yO₇) have been investigated by density functional theory calculations. It is found that the Nd incorporation into Gd-site leads to the formation of Gd₂Zr₂O₇-Nd₂Zr₂O₇ solid solutions, which remain the pyrochlore-type structures, whereas the introduction of Nd into Zr-site induces a pyrochlore-to-defect fluorite structural transition. Further calculations show that Nd substitution for Gd-site has a minor effect on the thermal–mechanical and electronic properties of Gd₂Zr₂O₇. However, incorporation of Nd into Zr-site results in smaller Young’s modulus, better ductility, stronger elastic anisotropy and lower Debye temperature than pure Gd₂Zr₂O₇. In addition, the incorporation of Nd into Zr-site results in an increasing number of electrons locating at the Fermi level with the increasing concentration of substitutional Nd atoms, which eventually leads to an insulating-to-metallic transition. This study suggests that incorporation of Nd into Zr-site can be an alternative way to tune the mechanical, electronic, and thermal properties of Gd₂Zr₂O₇.