TRANSIENT CURRENTS IN CHARGING AND DISCHARGING MODES IN ETHYL CELLULOSE

Transient current in vacuum aluminized ethyl cellulose foil samples of thickness 75 mu m were investigated in charging and discharging modes at different temperatures and fields. The occurrence of a peak in the current-time characteristics of charging current (I-c), and the depen dence of such currents on field, characterized by a negative resistanc e region and followed by a superlinear region, are considered to indic ate injection controlled transient currents modified by space-charge a rising from the localization of carriers in various traps. Carrier mob ility values calculated from a knowledge of the peak in the charging c urrent versus time characteristics were found to range from 10(-11) to 10(-9) cm(2)/V s. At times larger than the peak time, the charging cu rrent follows the relation I proportional to t(-n) at low temperatures with different poling fields (V-p). However, the current increases wi th time and finally tends to saturate for samples poled at higher temp eratures with higher values of field. The isochronal characteristics ( i.e, current-temperature plots at fixed times) constructed from discha rge current versus time plots are characterized by a peak at 70 degree s C or 100 degrees C, depending upon the poling field values.