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DF: Fachverband Dielektrische Festkörper

DF 16: Dielectric and ferroelectric thin films

DF 16.5: Vortrag

Mittwoch, 13. März 2013, 12:00–12:20, H11

Crystallization and ferroelectric activity of poly(vinylidene fluoride) thin films doped with ionic liquids — •Feipeng Wang¹, Peter Frübing¹, Alexander Lack¹, Andreas Taubert², and Reimund Gerhard¹ — ¹Applied Condensed-Matter Physics, Department of Physics and Astronomy, Faculty of Science, University of Potsdam, 14476 Potsdam-Golm, Germany — ²Institute of Chemistry, University of Potsdam, Potsdam-Golm, Germany

Ferroelectric PVDF films are obtained with doping of different types of ionic liquids (ILs). Selected ILs are used: 1-ethyl-3-methylimidazolium, combined with nitrate, or ethyl sulfate, or trifluoromethanesulfonate, respectively; as well as 1-butyl-3-methylimidazolium hexafluorophosphate. The doping of ILs enhances the crystallinity of PVDF. Crystalline β-phase (ferroelectric) dominant films are spin coated from solutions containing an IL of around 1 to 2 wt%. The content of β phase in PVDF decreases with larger anions. Additionally, high symmetry of the anions' charge centroid leads to lower polar phase (β or γ phase) content. For drop-cast films, the crystalline phases are non-uniform across the films' thickness.

The PVDF films exhibit remanent polarization values above 50 mC/m2. Large anions and/or cations produce PVDF films with lower conductivity and higher breakdown strength. The ferroelectric films show comparable pyroelectricity to stretched PVDF. The dipolar interaction between anions of ionic liquid and CH2 groups in the PVDF chain is considered to facilitate the formation of the β phase.