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 (Gd2−yNdyZr2O7 and Gd2Zr2−yNdyO7) 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.