Phase transition in corona charged α-PVDF samples in dry air

The constant current corona triode has been used to charge and monitor the surface potential buildup of α-PVDF (polyvinylidene fluoride) samples. Under dry conditions it is possible to pole the samples to sufficiently high electric fields so as to cause a phase change from the nonpolar α form to the polar α_p form. This phase transition is identified in the surface potential buildup by a plateau in which dipole orientation occurs, and can also be confirmed by X-ray diffractograms. A tentative theoretical model which takes into account ferroelectric polarization is developed to explain quantitatively the experimental results obtained for α_p-PVDF