Energy Loss Processes in Ferroelectric Ceramics

Effect of 90° domain walls on the low-field permittivity of PbZr(0.2)Ti(0.8)O3 thin films

We report on the contribution of 90° ferroelastic domain walls in strain-engineered PbZr(0.2)Ti(0.8)O(3) thin films to the room-temperature permittivity. Using a combination of phenomenological Ginzburg-Landau-Devonshire polydomain thin-film models and epitaxial thin-film growth and characterization, the extrinsic or domain wall contribution to the low-field, reversible dielectric response is evaluated as a function of increasing domain wall density. Using epitaxial thin-film strain we have engineered a set of samples that possess a known quantity of 90° domain walls that act as a model system with which to probe the contribution from these ferroelastic domain walls. We observe a strong enhancement of the permittivity with increasing domain wall density that matches the predictions of the phenomenological models. Additionally, we report experimentally measured bounds to domain wall stiffness in such PbZr(0.2)Ti(0.8)O(3) thin films as a function of domain wall density and frequency.

Characterization of (Fe'Zr,Ti - VO..). defect dipoles in (La,Fe)-codoped PZT 52.5/47.5 piezoelectric ceramics by multifrequency electron paramagnetic resonance spectroscopy

Ferroelectric 1 mol.% La(3)+ and 0.5 mol.% Fe(3)+ codoped Pb[Zr0(0.54)Ti0(0.46)]O(3) ceramics were studied by means of multifrequency electron paramagnetic resonance (EPR) spectroscopy. The obtained results prove that iron is incorporated at the [Zr,Ti]-site, acting as an acceptor and building a charged Fe'(Zr,Ti) - V(O)..)(.) defect dipole with a directly coordinated oxygen vacancy for partial charge compensation. This feature of the defect associates has hitherto been identified only in hard, exclusively Fe(3)+-doped PZT compounds. The present results show, however, that a similar defect association of the Fe3+ functional center with a V(O)..) also exists in soft, donor-acceptor (La(3)+,Fe(3)+)-codoped PZT. According to models developed by Arlt et al. electric dipoles from defect associates, such as the Fe'(Zr,Ti) - V(O)..)(.) defect associate, which may give rise to an internal bias field that is discussed being responsible for ferroelectric aging.