Ferroelectric properties of vinylidene fluoride/tetrafluoroethylene copolymer thin films consisting of needle-like crystals

Unique ferroelectric vinylidene fluoride (VDF)/tetrafluoroethylene (TeFE) copolymer thin films consisting of needle-like crystals were formed using Au-sputtered substrates. The VDF/TeFE films with a mixing ratio of 80 : 20mol% were melted at 170 degrees C for 30 min and then recrystallized at 116 degrees C for 300 min. The molecules in the resultant needle-like crystals had a beta-phase form and showed 200/110 orientation, while the direction of each needle-like crystal was random in-plane. The remanent polarization of the 450-nm-thick VDF/TeFE films consisting of the needle-like crystals were estimated to be 62mC/m(2) from the electric displacement vs electric field (D-E) hysteresis measurement at the applied field of 156MV/m and the frequency of 10Hz. The remanent polarization of 62mC/m(2) was approximately 50% larger than that of conventional VDF/TeFE films consisting of plate-like crystals. (C) 2016 The Japan Society of Applied Physics