Local symmetry-reduction in tetragonal (La,Fe)-codoped Pb[Zr0.4Ti0.6]O3 piezoelectric ceramics

Ferroelectric Pb[Zr0.4Ti0.6]O3 ceramics codoped with La3+ and Fe3+ at dopant concentrations of 1.0 and 0.5 mol. %, respectively, were investigated by means of multifrequency electron paramagnetic resonance (EPR) spectroscopy. The results prove that iron is incorporated at the [Zr,Ti]-site, acts as an acceptor and favors the creation of charged (Fe′Zr,Ti − V •• O ) • defect dipoles that may give rise to internal bias fields also for ‘soft’ piezoelectric compounds. In particular, the iron functional center site symmetry was investigated. A multi-site situation was observed in which the orientation of the (Fe′Zr,Ti − V •• O ) • defect dipole with respect to the orientation of spontaneous polarization is responsible for a (Fe′Zr,Ti − V •• O ) • center of ‘tetragonal’ and a different center of ‘rhombic’ local site symmetry. PACS numbers: 61.72.Ji, 61.72.Bb, 85.50.−n