Question

Explain the dielectric properties of solids.

Answer 1

Some important dielectric properties of crystals are as follows:

1. Piezoelectricity: The crystals, in which dipoles align in a way to produce a net dipole moment, exhibit piezoelectricity. When such a crystal is subjected to a mechanical stress, the crystal gets deformed and electricity is produced due to the displacement of ions. The electricity thus produced is called piezoelectricity.
2. Pyroelectricity: Some polar crystals, on being heated, produce a small electric current. The electric current thus produced is called pyroelectricity.
3. Ferroelectricity: In some of the piezoelectric crystals, the dipoles are permanently aligned even in the absence of an electric field. In such crystals, the direction of polarisation may be changed by applying an electric field. This phenomenon is called ferroelectricity. BaTiO₃, KH₂PO₄, Rochelle salt, etc., are some examples of ferroelectric crystals.
4. Antiferroelectricity: When the dipoles in alternate polyhedra point up and down, the net dipole moment of the crystal is zero. This phenomenon is called antiferroelectricity. PbZrO₃ is an antiferroelectric substance.