Dielectric Studies Essay

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3.2.8 Dielectric studies
Dielectric study of solid polymer electrolytes is an important technique for understanding the various relaxation processes, which are associated with the ion motion. The frequency dependent dielectric constant at room temperature for the PEO with different wt% of KCl is shown in Figure 3.14(a). It is evident from the figure that the dielectric constants are significantly high in the low frequency region due to electrode polarization and space charge effects and it obeys the non-Debye type behaviour [53, 54].
At higher frequencies, the dielectric constants are almost independent of frequency. This is because, at higher frequencies periodic reversal of the field takes place so rapidly that the charge carriers will hardly be able to orient
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The dielectric constant found decreases monotonically in the lower frequency and it is independent at higher frequency. The high value of the dielectric constant at low frequencies can be attributed to the accumulation of charge carriers near the electrodes and at higher frequency the dipoles or polar molecules are unable to orient themselves in the direction of the applied field, hence the dielectric constant appears to decrease or is steady with increasing frequency [58]. The dielectric constants (εꞌ & εꞌꞌ) were found to increases with temperature at a fixed frequency for all electrolyte films due to the greater freedom of movement of the dipole molecular chains of polymer electrolytes at high temperatures. At lower temperatures, the dipoles are rigidly fixed or tightly bound in the dielectric material; therefore the field cannot change the condition of the dipoles. As the temperature increases, the dipoles become comparatively free and they respond to the applied electric field causes the change in the induced energy at the dipole site and consequently enhance the dipole motion
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