Ferroelectric polarization, pyroelectric activity and dielectric relaxation in Form IV poly(vinylidene fluoride)
| Autor: | Takeo Furukawa, W.H. Abd. Majid, W. C. Gan |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Materials science
Polymers and Plastics Annealing (metallurgy) Organic Chemistry 02 engineering and technology Dielectric Coercivity 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Ferroelectricity 0104 chemical sciences Pyroelectricity Condensed Matter::Materials Science Dipole Crystallography Nuclear magnetic resonance Electric field Materials Chemistry Crystallite 0210 nano-technology |
| Zdroj: | Polymer. 82:156-165 |
| ISSN: | 0032-3861 |
| DOI: | 10.1016/j.polymer.2015.11.024 |
| Popis: | Ferroelectric, pyroelectric and dielectric properties were investigated for Form IV poly(vinylidene fluoride) (PVDF). We fabricated highly crystalline Form II thin films by spin-casting from acetone or methyl ethyl ketone followed by annealing at 155 °C and then converted into Form IV using a high electric field of 500 MV/m. We observed displacement (D) - electric field (E) hysteresis loop and attendant pyroelectric activity that supported ferroelectric polarization reversal in Form IV PVDF. The highly rounded D-E loop with a coercive field of 240 MV/m suggests that reversal of the dipole component perpendicular to TGT G ¯ chain requires very high field and progresses based on step-by-step switching of respective molecules. We also observed similar crystalline relaxations in Form II and IV suggesting that fluctuations of parallel dipoles in TGT G ¯ chains were not affected by chain packing. Simultaneous observation of polarization reversal and dielectric relaxation associated with two orthogonal directions (a- and c-axis) of crystallites is interpreted using the tilt angle between of the chain axis and sample surface. Microscopic features are discussed in terms of electric-field-induced and thermally-induced changes in TGT G ¯ conformational sequences. |
| Databáze: | OpenAIRE |
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