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Chapter V Dielectric Study of ……
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displacement current. The electric displacement can be separated into the
vacuum contribution and the contribution from the material as,
D = 0 E + P = 0 E + 0 E = 0 E (1 +) (5.14)
Where, P is the polarization of the medium and is its susceptibility. The
relative permittivity and susceptibility of a sample are related r = + 1.
5.4.1 Complex permittivity
In figure (5.6), the dielectric permittivity spectrum over wide range of
frequencies is presented. Various processes such as ionic and dipolar
relaxation, atomic and electronic resonance at higher energies are labeled.
Figure: 5.6 Dielectric permittivity spectrum (www.wikipedia.org).
Unlike in vacuum, the response of normal materials to external fields
depends on the frequency of the applied field. In fact, a polarization of
material does not respond instantaneously to an applied field. For this reason
the permittivity is often treated as a complex function of the frequency of the
applied field [2, 5]. The definition of complex permittivity is
= 0 * (ω) i t
E e
0 (5.15)
i t
D e
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