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[Zr_0.54Ti_0.46]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 g_i (i = x, y, z) of the Cu²⁺ centers in Pb[Zr_0.54Ti_0.46]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.