Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics are reviewed with the aim of providing an insight into different processes which may affect the behaviour of ferroelectric devices, such as ferroelectric memories and micro-electro-mechanical systems. Taking into consideration recent advances in this field, topics such as polarization switching, polarization fatigue, effects of defects, depletion layers, and depolarization fields on hysteresis loop behaviour, and contributions of domain-wall displacement to dielectric and piezoelectric properties are discussed. An introduction into dielectric, pyroelectric, piezoelectric and elastic properties of ferroelectric materials, symmetry considerations, coupling of electro-mechanical and thermal properties, and definitions of relevant ferroelectric phenomena are provided.

https://iopscience.iop.org/article/10.1088/0034-4885/61/9/002/pdf

Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics

Dielectric properties, lattice‐ and microstructure of ceramic BaTiO3 showing grain sizes of 0.3–100 μm were studied. At grain sizes <10 μm the width of ferroelectric 90° domains decreases proportionally to the square root of the grain diameter. The decreasing width of the domains can be theoretically explained by the equilibrium of elastic field energy and domain wall energy. The smaller the grains, the more the dielectric and the elastic constants are determined by the contribution of 90° domain walls. The permittivity below the Curie point shows a pronounced maximum er ≊5000 at grain sizes 0.8–1 μm. At grain sizes <0.7 μm the permittivity strongly decreases and the lattice gradually changes from tetragonal to pseudocubic.

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Dielectric properties of fine‐grained barium titanate ceramics

An overview of the state of art in ferroelectric thin films is presented. First, we review applications: microsystems' applications, applications in high frequency electronics, and memories based on ferroelectric materials. The second section deals with materials, structure (domains, in particular), and size effects. Properties of thin films that are important for applications are then addressed: polarization reversal and properties related to the reliability of ferroelectric memories, piezoelectric nonlinearity of ferroelectric films which is relevant to microsystems' applications, and permittivity and loss in ferroelectric films-important in all applications and essential in high frequency devices. In the context of properties we also discuss nanoscale probing of ferroelectrics. Finally, we comment on two important emerging topics: multiferroic materials and ferroelectric one-dimensional nanostructures. (c) 2006 American Institute of Physics.

/pdf/ferroelectric-thin-films-review-of-materials-properties-and-rc7umdkxk5.pdf

Ferroelectric thin films: Review of materials, properties, and applications

In response to the current environmental regulations against the use of lead in daily electronic devices, a number of investigations have been performed worldwide in search for alternative piezoelectric ceramics that can replace the market-dominating lead-based ones, representatively Pb(Zr
 x
 Ti1-x
 )O3 (PZT)-based solid solutions. Selected systems of potential importance such as chemically modified and/or crystallographically textured (K, Na)NbO3 and (Bi1/2Na1/2)TiO3-based solid solutions have been developed. Nevertheless, only few achievements have so far been introduced to the marketplace. A recent discovery has greatly extended our tool box for material design by furnishing (Bi1/2Na1/2)TiO3-based ceramics with a reversible phase transition between an ergodic relaxor state and a ferroelectric with the application of electric field. This paired the piezoelectric effect with a strain-generating phase transition and extended opportunities for actuator applications in a completely new manner. In this contribution, we will present the status and perspectives of this new class of actuator ceramics, aiming at covering a wide spectrum of topics, i.e., from fundamentals to practice.

Giant electric-field-induced strains in lead-free ceramics for actuator applications – status and perspective

The piezoelectric effect in ferroelectric single crystals and ceramics is investigated considering intrinsic (lattice), and extrinsic (originating mainly from displacement of domain walls) contributions. The focus of the study of intrinsic properties is on piezoelectric anisotropy, which was examined using the Landau-Ginsburg-Devonshire phenomenological theory. It is shown that the enhanced piezoelectric response along nonpolar directions, observed in many perovskite systems, is a consequence of the flattening of the Gibbs free energy profile. This flattening is common for temperature-, composition-, and external field-induced enhancement of the piezoelectric properties along nonpolar axes. A brief review of recent advances in understanding the origins of the piezoelectric nonlinearity, hysteresis, and frequency dispersion is also given.

Contributions to the Piezoelectric Effect in Ferroelectric Single Crystals and Ceramics

A proposed model which takes into account an elastic interaction between a polydomain grain and a surrounding ceramic matrix under weak external mechanical stresses has been used for evaluating a contribution from 90° domain wall displacements to piezoelectric and elastic constants of the perovskite ferroelectric ceramics. A difference between experimental and averaged constants of BaTiO3 ceramics can be explained by the estimated contribution.

The role of 90° domain wall displacements in forming physical properties of perovskite ferroelectric ceramics

This review concerns the experimental and theoretical publications devoted to the important problem of the large piezoelectric anisotropy in -based polarized ferroelectric ceramics.

https://iopscience.iop.org/article/10.1088/0022-3727/30/11/002/pdf

Ferroelectric ceramics with a large piezoelectric anisotropy

Maxwell-Wagner piezoelectric, dielectric and elastic relaxations in two-layer or multilayer serial piezoactive media are considered. As distinct from the oversimple model, described in literature, we derive exact solutions by taking into account mechanical boundary conditions, transversal piezoelectric response and elastic properties of layers. We first study the Maxwell-Wagner relaxation of elastic compliances and the contribution from piezoelectric coefficients and elastic constants of two layers to the value of the relaxation time. Methods for strengthening as well as eliminating the relaxations and for the giant enhancement of dielectric permittivity are specially reviewed.

https://iopscience.iop.org/article/10.1088/0022-3727/35/11/314/pdf

Maxwell-Wagner relaxation in piezoactive media

The elastic compliance coefficients, dielectric permittivities and piezoelectric constants of a BaTiO3 tetragonal crystal with periodically alternating layers of 180° domains were calculated. It was shown that the presence of 180° domain walls resulted in changes of a number of elastic and dielectric constants of the polydomain sample as compared with the single domain one. The propagation of elastic waves in the laminated crystal was considered. The frequency dependence of effective permittivity and the effect of domain structure on the piezoelectric behaviour of crystal were analysed.

A. V. Turik

Papers

The role of 90° domain wall displacements in forming physical properties of perovskite ferroelectric ceramics

Ferroelectric ceramics with a large piezoelectric anisotropy

Maxwell-Wagner relaxation in piezoactive media

Effect of domain structure on physical properties of ferroelectrics

The effect of 90° domain wall displacements on piezoelectric and dielectric constants of perovskite ferroelectric ceramics