Ac conductivity measurements were carried out on polycrystalline samples of a ferrimagnetic spinel (Zn0.44Mn0.56Fe2O4) and a ferroelectric perovskite (Sr0.25Bi4Ti3.25O12.75), in the temperature range 20–160 and 20–660 °C, respectively, and in the frequency range 5 Hz–13 MHz. The impedance response in both cases could be resolved into two contributions, associated with the bulk (grains) and the grain boundaries. An analysis by means of the ac conductivity power law showed evidence of a critical temperature of 132 and 536 °C, for the ferrimagnetic and the ferroelectric samples, respectively, which corresponds to the Curie temperature for each type of material. These results are interpreted in terms of the disorder increase approaching the phase transition.

Lanthanum doping of zirconium rich lead zirconate titanate gives rise to incommensurate, long‐period antiferroelectric structures. The structure of two stacking sequences in this incommensurate phase is determined using quantitative analysis of high‐resolution scanning transmission electron microscopy images, with the lead atom positions located with an exceptional precision of about 6 pm. This allows the estimation of local polarisation variations across the stacking units, and the polarisation varies in an approximately sinusoidal fashion along the stacking direction. The measured peak Pb atom displacements of about 28 pm and peak polarisation values of about 60 μC cm−2 match extremely well to reported values for the commensurate antiferroelectric PbZrO3 phase.

The electrical conductivity behaviour in the paraelectric state has been investigated in lanthanum modified lead zirconate titanate (PLZT) ceramics, considering the universal relaxation law. The contribution of conductive processes to the dielectric response for the low-frequency range was discussed taking into account the oxygen vacancies mechanism. The activation energies for the thermally hopping and conductivity processes were obtained. The results for the frequency dependence of the conductivity suggest at the oxygen vacancy hopping processes, due to relaxations in oxygen vacancy-related dipoles, being mainly responsible for the conduction behaviour in the studied system.

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Two modifications of lead titanate ceramic and the polyetherketoneketone polymer (PEKK) have been used to obtain two polymer/ceramic composites. The piezo-, pyro-, ferroelectric, and dielectric properties were studied. The calcium modified lead titanate/polyetherketoneketone (PTCa/PEKK) composite shows better piezo- and pyro-electric properties than that of the samarium and manganese modified lead titanate/polyetherketoneketone (PSTM/PEKK) composite. Also, a lower dielectric permittivity and remanent polarization values with a higher coercive field are obtained. The results are discussed considering the modifications made in the ceramic phases of each composite. The presented properties for both composites are still substantially lower than those in bulk ceramics.

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Ferroelectric ceramics are important materials with a wide range of industrial and commercial applications. Since the discovery of the phenomenon of ferroelectricity, they have been the heart and soul of several multibillion dollar industries, ranging from highdielectric-permittivity capacitors to developments in piezoelectric transducers, pyroelectric sensors, medical diagnostic transducers, electro-optical devices, etc. Materials based on barium titanate and lead zirconate titanate have dominated the field throughout their history. Actually, the ferroelectric ceramics from the Aurivillius family receive great attention due to their large remanent polarization, lead-free nature, relatively low processing temperatures, high Curie temperatures and excellent piezoelectric properties, which made them good candidates for multiple applications. This review presents a general overview of the progress in the studies on the ferroelectric ceramics from the Aurivillius family. The progress includes several aspects: (i) structural studies, (ii) dielectric and electric behavior, (iii) piezoelectricity, and (iv) pyroelectricity.

The details of the domain structure of the incommensurate antiferroelectric structure in La-doped zirconium-rich lead zirconate titanate have been revealed in detail for the first time. The structure is dominated by 60° domain boundaries close to {101} planes of the primitive perovskite cell; and tilts of the perovskite sublattice of about 0.5° are also noted at such boundaries consistent with a small tetragonal distortion of the primitive cell. Within each domain a streaked nanostructure is revealed under weak diffraction conditions perpendicular to the long b-axis of the incommensurate supercell, which appears to be a consequence of planar faulting perpendicular to this b-axis. 90° domain boundaries are also observed but are less frequent than 60° boundaries and in contrast to previous reports, these often have rather curved and irregular boundary planes. The close similarity of all these features, with the one exception of the streaked nanostructure, to the domain structure of the commensurate antiferroelectric PbZrO3, demonstrates the close relationship of the two phases and leads one to speculate that the atomic structures of the phases are also closely related.