Static and dynamic pyroelectric properties of PVDF

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Abstract
The pyroelectric properties of polyvinylidene fluoride (PVDF) have been investigated with a new procedure for the simultaneous measurement of the pyroelectric coefficient under quasistatic and dynamic conditions. The sample is heated at a uniform rate with an overlaid sinusoidal temperature modulation. The dc and the ac component of the electric current are recorded, and the dc and ac components of the temperature are measured with a thin film resistive bolometer. The quasistatic measured pyroelectric coefficient is higher than the dynamic one, with a quotient of both quantities up to three. The frequency dependence of the pyroelectric coefficient has been investigated down to 10−3 Hz, showing a contribution of free charges to the pyroelectric current for frequencies below the reciprocal dielectric relaxation time. The results show, that the polarization of the crystalline regions is locally compensated by charge, and that even a small change of the polarization is compensated within a time scale of 10−3 s.