Some features of the electric relaxation in PVDF and PVDF-PZT composites

It is shown that relaxation of the residual polarization in PVDF can be caused by spontaneous switching of a portion of the polarized volume to its initial electric state. The phenomenon is observed as Barkhausen's pulses. The duration of the pulse, the magnitude of a leap, and the switched volume per pulse are calculated. The current oscillations of infra-low frequency are also observed in partly poled samples, caused by a propagation of polarization waves (solitons) through the sample thickness. It is shown that relaxation of the unstable component of the residual polarization is responsible for the thermally stimulated currents in PVDF-PZT composites. The thermally stable one provides for the piezo- and pyroelectricity in the composite.