Internal fields in PT/PVDF-TrFE 0-3 composites

Composites of ferroelectrics have a promising potential for applications, as it is possible to obtain new properties by combining two different ferroelectric materials. The spontaneous polarization of lead titanate (PT) is about an order of magnitude higher than that of vinylidenefluoride-trifluoroethylene copolymer (PVDF-TrFE). Therefore, in order to polarize the PT inclusions in a PT/PVDF-TrFE 0-3 composite, the depolarizing field must be compensated to a large extent by a counter field due to charge accumulated at the interface between the matrix and inclusions. An internal field will arise within the composite when the accumulated charge is insufficient to generate a fully compensating counter field. To demonstrate the existence of such an internal field we have studied the pyroelectric activity of composites with 27 volume% of PT in 56/44 mol% PVDF-TrFE. In the temperature range around the ferroelectric phase transition of the copolymer, induced pyroelectric activity is observed. The internal field can be estimated from an analysis of the pyroelectric activity of the composite