Nonvolatile Storage Medium Made from PVDF
Regions with a permanent electrical polarization can form in ferroelectric materials. An external field can be used to change this polarization to a different direction. In this way, such materials can be used as nonvolatile storage media. In addition to inorganic ferroelectrics, polymer systems can also be used. Until now, these have consisted of a special copolymer made from PVDF and trifluoroethylene. Production of this copolymer is complex and thus relatively expensive. In addition, the material loses its ferroelectric properties at temperatures above 80°C. As a consequence, the stored data can no longer be accessed.
Scientists at the Zernike Institute for Advanced Materials at the University of Groningen (ZIAM) and the Max Planck Institute for Polymer Research have now found a simpler way to produce storage media from PVDF. Under certain processing conditions, the PVDF homopolymer is converted into a so-called delta phase that exhibits ferroelectric properties and is furthermore stable at elevated temperatures. With this production method, it is possible to use commercially available PVDF that is employed for membranes or medical devices, for instance. As a result, the PVDF films are relatively inexpensive. Moreover, the PVDF films retain the stored data up to temperatures of about 170°C.
A ferroelectric plastic transistor as well as a ferroelectric plastic diode have already been developed at the ZIAM. The objective of a project involving research groups from several European countries is to develop the plastic-based electronic components to marketability.