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Issue 4, 2020
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Structural control of the dielectric, pyroelectric and ferroelectric properties of poly(vinylidene fluoride-co-trifluoroethylene) thin films

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Abstract

The effects of solvents and temperature on the crystal formation were investigated for vinylidene fluoride/trifluoroethylene copolymer P(VDF-TrFE). Highly crystalline P(VDF-TrFE) thin films were fabricated by spin-casting using various polar solvents such as diethyl carbonate (DEC), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Ferroelectric polarisation reversal of the P(VDF-TrFE) was evidenced by a displacement (D)electric field (E) hysteresis loop measurement and supported by the presence of pyroelectric activity. The samples which were annealed above 100 °C gave elongated rod-like crystalline structures and the highest crystallinity, Xc of 83% was formed at 120 °C. Consequently, remnant polarisation (85 mC m−2) and the pyroelectric coefficient (30 μC m−2 K−1) were enhanced. Thus, annealing plays a substantial role in controlling the crystalline structure of P(VDF-TrFE) films regardless of the choice of solvent. Although, the crystalline structure control is almost independent of the solvent's polarity, the choice of solvent is essential in preparing a smoother film surface. Molecular dynamics of P(VDF-TrFE) are discussed from the observation of two dielectric relaxation processes, β and γ related to the segmental micro-Brownian and local modes, respectively. The complete ferroelectric polarization reversal caused a reduction in the dielectric polarization and reduced the lattice spacing of the 110/200 planes.

Graphical abstract: Structural control of the dielectric, pyroelectric and ferroelectric properties of poly(vinylidene fluoride-co-trifluoroethylene) thin films

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Supplementary files

Article information


Submitted
20 Mar 2019
Accepted
02 Jan 2020
First published
03 Jan 2020

Phys. Chem. Chem. Phys., 2020,22, 2414-2423
Article type
Paper

Structural control of the dielectric, pyroelectric and ferroelectric properties of poly(vinylidene fluoride-co-trifluoroethylene) thin films

C. Y. B. Ng, W. C. Gan, T. S. Velayutham, B. T. Goh and R. Hashim, Phys. Chem. Chem. Phys., 2020, 22, 2414
DOI: 10.1039/C9CP01556F

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