It is a physical property associated with antiferroelectric materials. In fact, these are ionic materials that can polarize without an external field (spontaneous polarization). As a result, the dipoles are aligned or arranged along alternating directions. That is, adjacent lines will be parallel in opposite directions. An electric field causes a phase transition in these materials. This phase transition causes large pattern stress and energy changes. Antiferroelectricity is closely related to ferroelectricity. They are contradictory to each other. So we have to know that ferroelectricity is also a physical property which is rapidly polarized. By varying the direction of the applied field we can reverse the direction of polarization. Therefore, the difference is the direction of the dipole after polarization. The former will align antiparallel and the latter will align in the same direction. The antiferroelectric property is stabilized by the ferroelectric property in a simple cubic pattern.
The entire macroscopic spontaneous polarization in antiferroelectric material is zero. The reason is that the closest dipoles will cancel each other. This property can emerge or vanish depending on various parameters. The parameters are external field, pressure, growth method, temperature etc. The antiferroelectric property is not piezoelectric. That is there is no change in mechanical character of the material by the application of external field. These materials usually have high dielectric constant. The dipole orientation of this material is similar to the chess board pattern which is shown below.
Examples of antiferroelectric materials are as follows:
- PbZrO3 (lead zirconate).
- NH4H2PO4 (ADP: Ammonium Dihydrogen Phosphate).
- NaNbO3 (Sodium Niobate).
Antiferroelectricity and Temperature:
The antiferroelectric property will disappear above a certain temperature. We can call it antiferroelectric Curie point. The materials and their Curie temperatures are shown in Table 1. The dielectric constant (relative permittivity) is investigated below and above this Curie point. This is done for first and second order transitions. In a second-order transition, the dielectric constant is constant across the Curie point. In both cases the dielectric constant should not be too high.
Double Hysteresis Loop:
A hysteresis loop of a perfect antiferroelectric material can be constructed as shown in Figure 2 below. The reversal of the spontaneous polarization of these materials gives double hysteresis loops. The applied external field is a low frequency AC field.
Application of Antiferroelectricity:
- MEMS application.
- Used in combination with ferromagnetic materials.
- High energy storage devices.
- Photonic application.
- Liquid crystal etc.