Sevenfold- and sixfold-coordinatedZr3+ions in cubic stabilized zirconia: Crystal-field approach

Crystal-field calculations of the energy structure of the 4d multiplet of the ${\mathrm{Zr}}^{3+}$ ion were carried out for a large number of configurations of the environment in the crystal lattice of cubic stabilized zirconia, starting from neutron-diffraction data. The presence of oxygen vacancies gives rise to sixfold- and sevenfold-coordinated sites where the crystal field is strongly distorted with respect to regular crystal sites and cannot be treated with the perturbative approximation of weak distortions. The problem of the assignment of the axial EPR signal and of the optical-absorption bands to sixfold- and sevenfold-coordinated sites is discussed.