3.3. Effect of temperature
In order to get information about influence of temperature on electrical behavior of water hyacinth plant, dielectric properties of its root (taken as a representative example) are investigated in the temperature rage (30–90 °C) as shown in Fig. 3 and Fig. 4. The permittivity (ε′) and dielectric loss (ε″) shown in Fig. 3, are found to increase with the rise in temperature and decrease with frequency. Further, they showed strong temperature dependent at higher temperatures and lower frequencies. This indicates that the contribution of dipole orientation would be insignificant [34]. The main contribution to ε′ in the low frequency region may be due to the electronic polarization. More evidence is provided at temperatures higher than 60 °C and frequencies lower than 1 Hz. Since, ε′ seemed to be almost constant (see the vertical dashed line in inset) while ε″ showed a sigmoidal increase with decreasing frequency, indicating the pure electronic conduction effect, i.e. dc conductivity (σdc). In this case, no contribution arises from pure electronic conduction to ε′ while ε″ = σdc/εoω increases linearly with decreasing frequency. Where εo is given for the permittivity of air (= 8.85 × 10− 12 F/m), ω (= 2πυ) is angular frequency of the applied electric field and υ is the field frequency. The strong temperature dependence of ε′ in the high-temperature region, may be related to the fact that at high temperatures the loss is dominated by thermally activated electron hopping but in the low-temperature region such an activated process is frozen out, resulting in a decrease of ε′ at low temperature [35].