Synergistic effects of stretching/polarization temperature and electric field on phase transformation and piezoelectric
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Synergistic effects of stretching/polarization temperature and electric field on phase transformation and piezoelectric properties of polyvinylidene fluoride nanofilms S. Debili1 · A. Gasmi1 · M. Bououdina2 Received: 17 February 2020 / Accepted: 23 March 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This study aims to investigate the dependence of crystalline structure and piezoelectric properties of polyvinylidene fluoride stretched films (up to four times their initial length) as a function of temperature, polarization under constant field as well as varying electric field at constant polarization temperature. X-ray diffraction analysis indicates that α → β phase transformation occurs below 80 °C; meanwhile, the crystallinity is improved with stretching temperature reaching 44% compared to 32% for un-stretched. FTIR analysis confirms the results obtained by XRD, as new functional groups, shift of peaks position as well as reduction in their relative intensity are observed. It is found that the piezoelectric coefficient (d33) decreases with increasing temperature, while it increases with the electric field. The obtained results are discussed on the basis of the dependence of (d33) as a function of phase (α + β + amorphous) composition and the degree of crystallinity associated with various vibrational modes and the arrangement of hydrogen and fluorine atoms (corresponding charge H+ and F−) from either sides of PVDF skeleton chains arising upon the influence of thermomechanical treatment, polarization and electric field. Keywords Polyvinylidene fluoride · Stretching temperature · Polarization · Phase transformation · Piezoelectric effect
1 Introduction Polyvinylidene fluoride (PVDF) is a semi-crystalline polymer that has been extensively investigated because it exhibits fascinating and unique properties including piezo-/pyro-/ ferro-electric, dielectric as well as mechanical [1–5]. Hence, it offers broad range of applications in biomedicine, sensors and biosensors, triggers, transducers and nonvolatile memory devices as well as other electrical and optical uses such as surface acoustic wave devices [6–14]. In general, PVDF consists of a mixture of an amorphous matrix with homogeneously dispersed tiny crystalline phases. Five polymorphic phases have been identified, namely α, β, γ, δ and ε. The molecular chain
* M. Bououdina [email protected] 1
Laboratory of Solid Physics ‑ LPS, Department of Physics, Faculty of Sciences, University Badji Mokhtar Annaba, BP 12, 23000 Annaba, Algeria
Department of Physics, College of Science, University of Bahrain, PO Box 32038, Zallaq, Kingdom of Bahrain
2
conformation of these phases has been verified within PVDF, trans–gauche–trans–gauche′ (TGTG′) for nonpolar α and polar δ, all trans planer zigzag (TTT) for polar β and (T3GT3G′) for polar γ and nonpolar ε [15–21]. The most commonly stable and largely investigated in the literature are α and β phases [22, 23]. The nonpolar α phase is the most common and is usually obtained by melt cry
