The negative piezoelectric effect of the ferroelectric polymer poly(vinylidene fluoride)

Ilias Katsouras, Kamal Asadi, Mengyuan Li, Tim B. Van Driel, Kasper S. Kjær, Dong Zhao, Thomas Lenz, Yun Gu, Paul W.M. Blom, Dragan Damjanovic, Martin M. Nielsen, Dago M. De Leeuw

Research output: Contribution to journalArticle

132 Citations (Scopus)

Abstract

Piezoelectricity describes interconversion between electrical charge and mechanical strain. As expected for lattice ions displaced in an electric field, the proportionality constant is positive for all piezoelectric materials. The exceptions are poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene (P(VDF-TrFE)), which exhibit a negative longitudinal piezoelectric coefficient. Reported explanations exclusively consider contraction with applied electric field of either the crystalline or the amorphous part of these semi-crystalline polymers. To distinguish between these conflicting interpretations, we have performed in situ dynamic X-ray diffraction measurements on P(VDF-TrFE) capacitors. We find that the piezoelectric effect is dominated by the change in lattice constant but, surprisingly, it cannot be accounted for by the polarization-biased electrostrictive contribution of the crystalline part alone. Our quantitative analysis shows that an additional contribution is operative, which we argue is due to an electromechanical coupling between the intermixed crystalline lamellae and amorphous regions. Our findings tie the counterintuitive negative piezoelectric response of PVDF and its copolymers to the dynamics of their composite microstructure.

Original languageEnglish
Pages (from-to)78-84
Number of pages7
JournalNature Materials
Volume15
Issue number1
DOIs
Publication statusPublished - 1 Jan 2016

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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