Effect of the air humidity on the corona polarization of β-PVDF films

The corona triode making it possible to charge polymeric foils with a constant current has proved to be a powerful method for studying charge storage and transport. For ferroelectric polymers it allows one to determine the coercive field and the remanent polarization. A special version of such a triode was developed for poling samples in a controlled atmosphere. The results show that for β-PVDF (polyvinylidenefluoride) samples the surface potential build-up is dependent on the air humidity. For a dry air atmosphere, the polarization clearly shows the ferroelectric behavior of the PVDF sample. A tentative explanation for the saturation of the potential build-up dependence on the humidity takes into account the increase in conductivity due to the water in the bulk of the polymer