Antiferroelectric crystal

Antiparallel dipole ordering to produce an antiferroelectric crystal is also commonly encountered. Other ways of ordering electric dipoles are not so well characterized, but parallels with the situation in magnetic materials occur. 

In some perovskite ceramics, the instability that occurs at the Curie temperature is not ferroelectric but rather antiferroelectric. In antiferroelectric crystals, the neighboring lines of ions are displaced in opposite senses which creates two alternating dipole sublattices of equivalent but opposite polarization. Consequently, the net polarization is zero, and the dielectric constant does change at the transition temperature. Examples of antiferroelectric crystals are WO3, NaNbO, PbZrO, and PbHfOj. 

Some important antiferroelectric crystals are listed here with their Curie Temperatures T. The last column gives the constant which appears in the Curie-Weiss law describing the dielectric constant of these materials above the Curie Temperature ... 

Figure 6.14 Antiferroelectric behaviour schematic (a) parallel array of spontaneous polarisation dipoles characteristic of a ferroelectric crystal (b) antiparallel array of dipoles in an antiferroelectric crystal...

Liquid crystal ferri and antiferroelectrics have many features discovered for years of comprehensive studies of corresponding crystalline substances. Thus, it would be convenient and instructive to begin with a short introduction in the structure and properties of antiferroelectric crystals. A difference between ferro-, ferri and antiferroelectrics is schematically shown in Fig. 13.15, where the three very simplified... 

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