Space charge and dipoles in polyvinylidenefluoride

The properties of space charge (homocharge) and dipoles (heterocharge) in v arious electrets have been in the focus of interest since the investigation s of B. Gross on carnauba wax. In this article we present a review on the r ole and the interaction of charges and dipoles in the polymeric electret po lyvinylidenefluoride (PVDF). It covers the importance of charge injection f or the orientation of the dipoles at low fields as well as the role of char ge trapping for the stabilization of the polarization. Investigations of th e thermal stability of the polarization and the charge balance are leading to a detailed analysis of the depth and localization of the charge traps. F urthermore, it was possible to identify the space charge as ions created el ectrochemically during the poling process.