Measurement of the pyroelectric coefficient of poly(vinylidene fluoride) down to 3 K

Abstract

The temperature dependence of the pyroelectric coefficient (Formula presented) of polyvinylidene fluoride ((Formula presented)) was measured from 307 K to the previously unexplored region of 3 K. The measurements were performed on a film of oriented (Β-phase) (Formula presented) by monitoring its surface charge response to quasistatic heating and cooling transients. The data exhibit a pure cubic temperature dependence from 3 to 6 K with no evidence of a linear term. This is consistent with the prediction by Szigeti and the Debye limit, respectively, for the primary (i.e., strain-free) and secondary contributions to pyroelectricity. The data from ∼20 to ∼150 K, which include the region of largest change, are well fit by an exponential function (i.e., (Formula presented)(Formula presented)), corresponding to a thermal activation energy of θ=(25.9±0.06) K. Our data for (Formula presented), from 100 to 250 K, are approximately proportional to the thermal expansion coefficient, recently published by Hartwig, which indicates that the observed pyroelectricity is dominated by piezoelectric (i.e., secondary) contributions in that temperature regime. © 1997 The American Physical Society.