Polarization reversal and thermally stimulated discharge current in a vinylidene fluoride trifluoroethylene copolymer

Polarization reversal in a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene is observed in a circuit with a large time constant. The contributions of the ferroelectric and nonferroelectric phases in the copolymer can be identified in the reversal currents. If the copolymer is poled at high temperature, then reversal currents measured subsequently at lower temperatures display an asymmetry which is consistent with the accumulation of space charge in the copolymer. Shifts in successive reversal currents indicate that this space-charge accumulation dissipates slowly during polarization reversal. Thermally stimulated discharge currents from poled samples, and from samples with partially reversed polarization, indicate that there may be two populations of dipoles in the copolymer which are affected to different degrees by the space charge.