Investigations on the EPR g factors and local structures for the orthorhombic and tetragonal Cu2+ centers in Pb[Zr0.54Ti0.46]O3.

The defect models of the orthorhombical and tetragonal Cu2+ centers in Pb[Zr0.54Ti0.46]O3 are attributed to Cu2+ ions occupying the sixfold coordinated octahedral Ti4+ site with and without charge compensation, respectively. The electron paramagnetic resonance (EPR) g factors gi (i = x, y, z) of the Cu2+ centers in Pb[Zr0.54Ti0.46]O3 are theoretically studied by using the perturbation formulas of a 3d9 ion under orthorhombically and tetragonally elongated octahedra. Based on the calculation, the impurity off-center displacements are about 0.253 and 0.162 Å for the orthorhombical and tetragonal Cu2+ centers, respectively. Meanwhile, the planar Cu2+-O2- bonds are found to experience the relative variation ΔR (≈0.102 Å) along the a- and b-axes for the orthorhombical Cu2+ center due to the Jahn-Teller (JT) effect. The theoretical EPR g factors based on the above local structures agree well with the observed values.