The crystallinity and piezoelectric properties of spray-coated films of P(VDF70-TrFE30): effect of film thickness and spin-crossover nanofillers
Résumé
Spray coating the ferroelectric polymer P(VDF-TrFE) appears as an attractive approach for the fabrication of electromechanical transducers. However, it is important to elucidate how the crystallinity and associated piezoelectric properties depend on the coating thickness and additives. To this aim, we have spray-coated various substrates both with pure and nanocomposite films of the 70-30 % copolymer in a broad thickness range (200 nm – 30 µm). Using X-ray diffraction, differential scanning calorimetry, Raman spectroscopy and atomic force microscopy, we show that the obtained films are dense and homogeneous with ca. 50-60 % crystallinity, which consists of a majority polar β-phase, with slight alterations in the sub-micrometer thickness regime. Robust piezoelectricity and ferroelectricity are revealed at room temperature through both local hysteresis loops and lithography experiments using the piezoresponse force microscopy technique. After poling, the piezoelectric d33 coefficient displays values up to -19 and -11 pC/N for the pure copolymer and the composite, respectively. For a 33 vol% load of inorganic spin-crossover nanofiller, the switching properties are substantially improved and a coercive voltage <10 V is demonstrated for micrometric films. Overall, this approach appears as a promising way for the in-situ integration of high quality piezopolymer films into complex transducer geometries for sensing, actuating and energy harvesting purposes.
Domaines
Matériaux
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Angulo-Cervera, Crystallinity and piezoelectric properties, 2022.pdf (1.59 Mo)
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