Influence of annealing temperature on ferroelectric and electromechanical responses of P(VDF-TrFE-CFE-FA) tetrapolymer

We study the influences of the annealing temperatures on the ferroelectric and electromechanical (EM) responses of the relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene- fluorinated alkyne) (PVDF-TrFE-CFE-FA) tetrapolymer. The results show that only within a narrow annealing temperature window (<10 °C) around 120 °C, the tetrapolymer exhibits a pure relaxor phase and displays the highest EM response. Films annealed outside of this narrow temperature window contain a small amount of local polar-phase mixed with the relaxor phase. These results reveal that the tetrapolymer composition in the study is near a critical transition region between polar (ferroelectric) and non-polar (relaxor) chain condensed state which has vanishingly small energy barriers between different chain condensed state, thus a small electric field generates a large EM response. The films annealed outside of the narrow temperature window have a broad energy landscape that includes both non-polar and polar chain condensed state. Hence, small changes in annealing temperature result in different ferroelectric and electromechanical responses.