Berlin 2012 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 13: Poster II
DF 13.9: Poster
Mittwoch, 28. März 2012, 15:00–17:30, Poster E
Ionic-Liquid Promoted Crystalline β Phase in Polyvinylidene Fluoride Nanofilms — •Alexander Lack, Feipeng Wang, Peter Frübing, Werner Wirges, and Reimund Gerhard — Applied Condensed-Matter Physics, Department of Physics and Astronomy, Faculty of Science, University of Potsdam, Karl-Liebknecht-Strasse 24- 25, 14476 Potsdam-Golm, Germany
Up to now it is immensely difficult to obtain sub-micrometer thin films of polyvinylidene fluoride (PVDF) in the ferroelectric β phase. We present a novel way to achieve β-phase PVDF sub-micrometer thin films that were obtained by spin coating from a solution containing a small portion of the ionic liquid 1-ethyl-3-methylimidazolium nitrate [EMIM][NO3]. After drying and annealing at temperatures above 100 ∘C the films showed strong ferroelectric hysteresis with a remanent polarization of maximum 76 mC/m2 and a coercive field of 200 MV/m. The pyroelectric coefficient was measured to 17 µC/(m2K) at 30 ∘C. The impact of [EMIM][NO3] on the crystallization behavior of PVDF, with particular attention to the occurrence and ratio of the ferroelectric β phase, was confirmed using infrared spectroscopy and X-ray diffraction. The surface morphology was determined using atomic force microscopy and scanning electron microscopy. They show that under the influence of ionic liquids no α-phase spherulitic crystallites are visible and the size of the crystalline regions decreases from about 10 to 2 µm. The ferroelectric β phase is assumed to be promoted by Coulomb interaction between NO3− anions and the molecular dipoles of PVDF.