Welcome Session 1 Relaxor Structure and Dynamics Chair –

The effect of electron irradiation on the ferroelectric properties ofLangmuir-Blodgett films of the copolymer poly(vinylidene fluoride-trifluoroethylene) isinvestigated using 1.26 MeV electrons with dosages from 16 to 110 Mrad. Films wereirradiated in the ferroelectric state to investigate the effect of defect introduction inultrathin films. Electron irradiation is known to have significant effects on theelectromechanical properties of PVDF copolymer films. We report the effects ofirradiation on phase transition temperature, polarization, and crystallinity in ultrathin(18-90 nm) Langmuir-Blodgett films. The films retain bistable ferroelectric polarizationup to dosages of 90 Mrad. The main effect of irradiation is reduction of crystallinity andaverage polarization at a rate of –0.8% per Mrad, indicating a steady conversion of thefilm to an amorphous, non-ferroelectric form. Figure 1 shows the reduction in the totalcrystallinity and the switchable remnant polarization as a function of dosage, revealing astrong correlation between crystallinity and ferroelectric polarization. This indicates thatthe crystalline material remains ferroelectric after irradiation. Previous studies haveshown a large re-conversion of paraelectric material to ferroelectric material underelectric field, which may be partially responsible for the giant electrostriction in thesematerials. It is unknown how stable such a conversion may be, however our pyroelectricmeasurements indicate the polarization is stable for at least 36 hrs.