  Using short circuit and open circuit modifications of the thermally
stimulated depolarization current technique, relaxation currents have been
measured in corona poled copolymer of vinylidene fluoride with
tetrafluoroethylene in samples stored after poling for either 1 day, or 16
month. Two well structured peaks observed in aged samples were attributed to
relaxation of electret and ferroelectric components of the remnant
polarization. In fresh samples the two components were mixed forming one broad
peak. Relaxation of the space charge caused inversion of the current in the
open circuit mode both in fresh and in aged samples. Space charge peaks
extracted from the total current by appropriate calculations have shown that
the trapped charges were more stable than the polarization. It was suggested
that both the electret and the ferroelectric components of the remnant
polarization were accompanied by either space, or surface charges.
