Ferroelectric behavior

Above a temperature called the Curie temperature, Tc, ferroelectric behavior is lost, and the material is said to be in the paraelectric state in which it resembles a normal insulator. 

In addition, many of the ferroelectric solids are mixed ions systems, or alloys, for which local disorder influences the properties. The effect of disorder is most pronounced in the relaxor ferroelectrics, which show glassy ferroelectric behavior with diffuse phase transition [1]. In this chapter we focus on the effect of local disorder on the ferroelectric solids including the relaxor ferroelectrics. As the means of studying the local structure and dynamics we rely mainly on neutron scattering methods coupled with the real-space pair-density function (PDF) analysis. 

Matsui H, Tsuchiya H, Suzuki T, Negishi E, Toyota N (2003) Relaxor ferroelectric behavior and collective modes in the 7t-d correlated anomalous metal )l-(BEDT-TSF)2FeCl4. Phys Rev 668 155105/1-10... 

Furthermore this method can be applied to fast pulse measurements, which are also of great interest in view of memory applications. An example is shown in Figure 17.17. This method can also be applied as small signal measurements on small structures, e.g. C(V) measurements on sub-micron capacitors, and is of great interest to gain further insight in ferroelectric behavior in the nano-scale [12], [13],... 

The unique dielectric properties and polymorphism of PVDF are the source of its high piezoelectric and pyroelectric activity.75 The relationship between ferroelectric behavior, which includes piezoelectric and pyroelectric phenomena and other electrical properties of the polymorphs of polyvinylidene fluoride, is discussed in Reference 76. 

Most nonferroelectric oxides and fluorides fall in this category of well-behaved compounds, but some materials exhibit larger deviations. Such deviations between observed and calculated dielectric constants can frequently be traced to factors which are known to increase k ionic or electronic conductivity, ferroelectric behavior, the presence of H2O or CO2 in chaimels or large cavities, or the presence of dipolar impurities other than H2O. A further cause of large deviations from additivity is the presence of rattling or compressed cations having unusually large or small cation polarizabilities, respectively. 

Ferroelectric Behavior. Ferroelectric substances are those which have a stable, permanent polarization. They are of interest here because H bonding is one of the important ordering mechanisms responsible for permanent polarization. 

Cohen RE (1992) Origin of ferroelectricity in oxide ferroelectrics and the difference in ferroelectric behavior of BaTiOs andPbTiOs. Nature 358 136-138... 

This compound was the first crystallographically characterized trichlorostannite salt of an amino acid. It crystallizes in the chiral 12 space group and exhibits ferroelectric behavior. Although 11 does not possess the push-pull electronic character required for large NLO efficiency, a powdered sample has provided an SHG response about 0.8 times that of urea at 1.064 qm. Although the origin of the optical... 

Ferroelectric behavior can be obtained by two mechanisms via the relative displacement of the anion and cation sublattices against each other (classical... 

Barium titanate is of particular interest, since it shows remarkable ferroelectric behavior. The reason for this is understood in terms of the structure. Here the ion, Ba2+, is so large relative to the small ion, Ti4+, that the latter can literally rattle around in its octahedral hole. When an electric field is applied to a crystal of this material, it can be highly polarized because each of the Ti4+ ions is drawn over to one side of its octahedron thus causing an enormous electrical polarization of the crystal as a whole. 

Guo S, Zhao XZ, Zhuo Q, Chan HLW, Choy CL (2004) High electrostriction and relaxor ferroelectric behavior in proton-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Appl Phys Lett 84 3349... 

---