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We investigate nonlinear conduction in aromatic polyurea thin films and its influence on the dielectric applications over a broad temperature range. The experimental data indicate that several high field conduction mechanisms coexist in the polymer films and one conduction mechanism may dominate over the others depending on different temperatures. The results also reveal that owing to the non-linear increase of the conduction loss with field, the dielectric loss at high field can be many orders of magnitude larger than that at low field. Therefore, besides the electrical breakdown strength, the conduction loss at high field and their temperature dependence behavior are other key factors in developing polymer dielectric materials for high energy density dielectric applications over a broad temperature range. [ABSTRACT FROM AUTHOR]

Ferroelectric materials are intrinsically multifunctional and have found a broad range of applications. A new class of semicrystalline terpolymers comprising vinylidene fluoride (VDF), trifluoroethylene (TrFE), and 1, 1-chlorofluoroethylene (CFE), were prepared at Institut de Saint-Louis (ISL) via a suspension polymerization process. Relevant studies and results show that this class of electroactive polymers offers unique properties in comparison with other ferroelectric polymers. The terpolymer exhibits high electrostrictive strain (x>7%) with relatively high modulus (>0.3GPa). It has been also observed that the large electrostrictive strain is nearly constant in the temperature range from 20 to 80 °C. The high room temperature relative dielectric constant (∼ 50), which is the highest among all the known polymers), high induced polarization (∼ 0.05 C/m²), and high electric breakdown field (>400 MV/m) lead to very high volume efficiency for the electric energy storage operated under high voltage (∼ 10 J/cm³). [ABSTRACT FROM AUTHOR]

This paper investigates the relaxor ferroelectric polymer—poly(vinylidene fluoride/trifluoroethylene/chlorofluoroethylene) terpolymer for energy storage capacitors. It is found that the high dielectric constant (> 50 at 1 kHz) and high reversible polarization in the terpolymer lead to a high electric energy density ∼ 10 J/cm³, achieved under an electric field of more than 350 MV/m. The high dielectric constant also causes the polarization saturation at fields much below the breakdown field and whereby the discharged energy density increases nearly linearly with applied field, distinctively different from the low dielectric constant linear dielectric polymers whose energy density rises with square of the applied field. The strong frequency dispersion and nonlinear polarization response (polarization saturation) of the relaxor terpolymer result in a low effective capacitance at the beginning of the discharge and the effective capacitance increases with time during the discharge. Furthermore, due to the frequency dispersion and nonlinear effect, the discharged energy density of the terpolymer to a resistor load RL increases with RL. A large RL will lead to high discharge efficiency in the terpolymer capacitor. [ABSTRACT FROM AUTHOR]