Question

Why dielectric constant becomes maximum at paraelectric to ferroelectric transition?

Answer 1

Answer:

Dielectric polarization in nonconductors has mostly two causes, namely electronic polarizability (electrons shifting within molecules) and orientational polarizability (dipolar molecules rotating or flipping, or ions changing places). The first effect has a rather weak temperature dependence, the second a rather pronounced one.

In a *polar* medium, high temperature disturbs the alignment of dipoles in an outer field: the dielectric constant decreases with temperature. In a *ferroelectric* medium, the dipoles are already aligned and, unless the outer field is very strong, thus do not contribute to the orientational polarizability. High temperature disturbs the ferroelectric alignment and produces molecules that are free to reorient in an external field, and these contribute to the dielectric constant.

Well, this is a kind of very simplistic explanation, but it may give you an idea which forces are at work

Answer 2

Dielectric polarization in nonconductors has mostly two causes, namely electronic polarizability (electrons shifting within molecules) and orientational polarizability (dipolar molecules rotating or flipping, or ions changing places). The first effect has a rather weak temperature dependence, the second a rather pronounced one.

In a *polar* medium, high temperature disturbs the alignment of dipoles in an outer field: the dielectric constant decreases with temperature. In a *ferroelectric* medium, the dipoles are already aligned and, unless the outer field is very strong, thus do not contribute to the orientational polarizability. High temperature disturbs the ferroelectric alignment and produces molecules that are free to reorient in an external field, and these contribute to the dielectric constant.

Well, this is a kind of very simplistic explanation, but it may give you an idea which forces are at work.