Disorder-induced optical and paramagnetic properties in zirconium dioxide: role of low symmetry crystal fields

The paramagnetic and optical properties of sixfold coordinated Zr3+ ions (T centers) in x-ray-irradiated yttria-stabilized zirconia have been investigated. We propose the attribution of the optical absorption to intracenter transitions as suggested by optical bleaching experiments. Wave functions and energy levels of the possible T-center configurations have been determined by supposing a disorder-induced distribution of oxygen displacements around the anionic vacancies. Electric dipole matrices of these defect structures are evaluated in order to determine the oscillator strength of optical transitions within the 4d1 multiplet. It is shown that local axial distortions without inversion symmetry account for the experimental features of the optical absorption and the paramagnetic resonance spectra. © 1995 The American Physical Society.