Complex dielectric constant behavior through

Dielectric spectroscopy is a technique which allows one to evaluate the complex dielectric permittivity e = e — ie" as a function of frequency and temperature, where e is the dielectric constant and e" is the dielectric loss [3,12]. A schematic view of a dielectric spectroscopy experiment is shown in Fig. 21.3. A dielectric sample of thickness d and area A is subjected to an alternating electric field of angular frequency w. Through measurements of the complex impedance of the sample it is possible to experimentally determine e [12,18-20]. Dielectric spectroscopy is a very suitable method to study molecular dynamics in polymers above Tg. In this case, segmental motions of the polymeric chains give rise to the so called cc-relaxation process, which can be observed as a maximum in e" and a step-Uke behavior in e as a function of frequency. Both, the intensity of the a relaxation, and the frequency of maximum... 

Additionally, many supplementary measurements assist in characterizing conductivity behavior, and thus help in establishing models. These include, for instance, the complex microwave-region dielectric constants of the material, and Reflectance measurements from the Visible through the far-IR. 

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