Non-Isothermal Depolarization Current Studies in Kapton-H Thermoelectrets

Thermally stimulated depolarization current characteristics of Kapton-H electrets are studied in the temperature range 303 to 573 K as functions of the polarizing field (133.3 to 500.0 kV cm−1), polarizing temperature (333 to 453 K), polarizing time (2.7 × 103 to 16.2 × 103 s), specimen thickness (2.5 × 106 to 12.5 × 106 nm), heating rate (0.017 to 0.10 K s−1), and storage time (0 to 720 h). The TSDC spectra comprise three maxima in all, namely, β, α, and ρ with their respective locations around 373, 453, and 553 K. These are attributed to dipole-orientation, motion of space charges, and surface charge injection, respectively. A shoulder (β′) emerging around 343 K is suggested to be akin to the main β-peak. The space-charge peak is found to be more sensitive to the forming and storage parameters than to that involving dipoles. The observed dependence of the peak temperature as well as the activation energy for various peaks on polarizing temperature and time is indicative of a continuous distribution of relaxations.