Origin of the strong temperature effect on the piezoelectric response of the ferroelectric (co-)polymer P(VDF70-TrFE30)

The electroactive (co-)polymer poly(vinylidene fluoride(70)-trifluorethyline(30)) is predestined for applications in flexible and soft electronic devices. However, the piezoelectric properties are highly temperature sensitive and so far, reported results cannot provide an explanation for their strong temperature dependence. For this purpose, we investigate the impact of temperature on important electrical, mechanical and electromechanical properties. For instance, both the electric-field- and the load-induced piezoelectric response characteristics were determined using micromachined capacitor-type test structures. Our results show that the piezoelectric performance of the polymer is strongly temperature-dependent even before the phase transition from the ferroelectric to the paraelectric regime. Starting from 25 degrees C, we measured an increase in the piezoelectric constant d(33) up to 150% with increasing temperature up to 80 degrees C. We show that the highly increasing piezoelectric response of the polymer is directly linked to the temperature dependence of its elastic modulus and polarization.