Effect of texturing conditions on the ferroelectric characteristics of vinylidene fluoride-tetrafluoroethylene copolymer films

Isometric annealing of ferroelectric films of a vinylidene fluoride-tetrafl uoroethylene copolymer uniaxially drawn at a low temperature is accompanied by noticeable enhancement of both remanent and spontaneous polarization. I n addition, this leads to some decrease in the coercive field. The analysis of optical data shows an increase in the full orientation upon annealing. As follows from spectroscopic data, the annealing leads to an increase in c rystallinity simultaneously with an increase in the perfection of the cryst als formed by drawing. Postcrystallization upon annealing proceeds via the mechanism of transition to the ordered state of amorphous-phase chains occu rring in the trans zigzag conformation. A necessary condition for the afore mentioned structural changes upon annealing is high orientation of the amor phous-phase chains in the original (before annealing) textured copolymer fi lms. The annealing temperature providing the formation of highly oriented p erfect structure has an optimal value. At high annealing temperatures, a de crease in the orientational ordering is observed. This decrease is ascribed to the possibility of transition of ferroelectric to paraelectric crystals , which have less dense packing, at such temperatures. ne occurrence of thi s transition is validated by shifting the Curie point to lower temperatures by an applied mechanical stress.