Pyroelectricity in Oriented Polytrifluoroethylene

Poling of oriented polytrifluoroethylene (PTrFE) was found to produce pyroelectricity which showed anomalous behavior and formation conditions identical to those in unoriented samples. The pyroelectric activity in oriented PTrFE was greatly enhanced when the poling temperature was low but was reduced as the poling temperature was raised, contrary to the behavior of ordinary thermoelectrets. The enhancement of the pyroelectricity is attributed to a greater increase of the new crystalline region and to the orientation effect, which aligned the dipoles along the electric field. The reduction of the pyroelectricity is attributed to an increase in the degree of chain orientation, which aligns the polar axis parallel to the film plane. This behavior depended strongly on the state of the amorphous region from which the new crystalline region carrying the spontaneous polarization grew.