So far, we have discussed linear dielectrics whose dielectric constant increases linearly with the applied field accompanied by an increase in the polarization depending upon the presence of polarization mechanisms in the materials.

In addition, there are a few special classes of dielectric materials which show large dielectric constants, non-zero polarization in the absence of electric field and nonlinearity in the dielectric constant.
These also show extraordinary special effects such as

• Coupling of strain and electric field (piezoelectric ceramics),

• Temperature dependence of the polarization (pyroelectric ceramics) and

• Presence of large polarization in absence of electric field i.e. spontaneous polarization (ferroelectric ceramics).

Most of these materials happen to be oxides and as you can very well understand now, these properties will be greatly affected by the defect chemistry and process variables.

The presence of these features makes these materials extremely useful for a variety of applications such as sensors, actuators, transducers, temperature detectors, imaging, permanent data storage etc.
In this module, we will discuss origin of these properties with a crystallographic and thermodynamic framework and associated mathematical representations along with a few examples of materials and devices.

The Module contains:

Suggested Reading:

• Principles of Electronic Ceramics, by L. L. Hench and J. K. West, Wiley

• Principles and applications of ferroelectrics and related materials, M. E. Lines and A. M. Glass, Oxford University Press

• Electroceramics: Materials, Properties, Applications, by A. J. Moulson and J. M. Herbert, Wiley