Can charge cause dielectric hysteresis? Observations on non-ferroelectric α-PVDF

Under suitable conditions, hysteresis of the current or of the polarization can be observed as a function of the electric field during poling of ferroelectric polymer films. This behavior has been investigated extensively, and was explained for various ferroelectric polymers with the well-known theory of ferroelectrics. The present work, however, indicates that poling of polymers that contain excess charges but no polar crystallites, sometimes leads to a similar hysteresis behavior. In support of this finding, we present and discuss current measurements during the electric poling of α-polyvinylidenefluoride (PVDF) films and compare the results to the respective behavior of ferroelectric β-PVDF films in which charge effects play quite a different role