In recent years, the stability field of a monoclinic phase at the morphotropic phase boundary in lead zirconate titanate, Pb͓Zr 1−x Ti x ͔O 3 , has been under discussion. In the present study, we investigated samples in the compositional range between 0.40ഛ x ഛ 0.475 and x = 0.55 using high-resolution synchrotron x-ray diffraction in combination with transmission electron microscopy and electron paramagnetic resonance to correlate average structure and microstructural information. It is shown that the microstructure plays a crucial role in the analysis of diffraction data. The appearance of intensity in diffraction patterns formerly linked to a monoclinic phase ͓B. Noheda et al., Phys. Rev. B 61, 8687 ͑2000͔͒ can directly be correlated to a miniaturization of the average domain structure of the material visible in the presence of nanodomains. The internal symmetry of the nanodomains is not necessarily monoclinic due to coherence effects in diffraction and is discussed with respect to martensitic theory.
Universal scaling features of polarization switching are established experimentally in rather different classes of disordered ferroelectrics: in well-studied lead-zirconate titanate (PZT) ferroelectrics, in recently synthesized Custabilized 0.94(Bi 1/2 Na 1/2 )TiO 3 -0.06BaTiO 3 (BNT-BT) relaxor ferroelectrics, and in classical organic ferroelectrics P(VDF-TrFE). These scaling properties are explained by an extended concept of an inhomogeneous fi eld mechanism (IFM) of polarization dynamics in ferroelectrics. Accordingly, disordered ferroelectrics exhibit a wide spectrum of characteristic switching times due to a statistical distribution of values of the local electric fi eld. How this distribution can be extracted from polarization measurements is demonstrated. Generally, it is shown that the polarization response is primarily controlled by the statistical characteristics of disorder rather than by a temporal law of the local polarization switching.
The composition dependent variation of domain configuration and size in Pb(Zr1−xTix)O3 (PZT) has been investigated in a detailed transmission electron microscopy study in the range of 0.40⩽x⩽0.55. Single phase composition, Pb(Zr0.45Ti0.55)O3 and Pb(Zr0.60Ti0.40)O3, the former belonging to the tetragonal, the latter to the rhombohedral phase, feature small microdomain widths coupled with a pronounced bimodal domain distribution. Samples with compositions around the morphotropic phase boundary exhibit a decrease of bimodal distribution and an increase in microdomain width associated with nanodomain formation. The investigation of micro- and nanodomains, as well as the bimodal distribution of microdomains in undoped PZT ceramics, with respect to composition, is reported. We define nanodomains as “domains arranged within microdomains possessing a width of a few nanometers.” The strict alternation of the two orientation variants of microdomains is denoted as “bimodal domain distribution,” and is characterized by narrow and broad microdomains, which join each other in turn.
Bipolar cycling of lead zirconate titanate ceramics can lead to massive material damage in regions close to the electrode. The damaged region can be identified by color changes, and the microstructure in this region shows signs of interface melting. This damaged region can screen the sample volume from the applied voltages and reduced fields are applied to the undamaged part of the sample. This has two effects. The first one is that the bulk is effectively subjected to smaller fields, but the measured parameters are assigned to the applied field, yielding apparent fatigue curves. The second effect is that with further cycling, field screening protects the bulk of the sample from fatigue due to the reduced effective fields. If the damaged region is mechanically removed and the ferroelectric hystereses are measured again, nearly unfatigued parameters are obtained.
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