POLARIZATION AND ELECTRIC-FIELD DISTRIBUTION IN THERMALLY POLED PVDF AND FEP

In the present paper, heat wave (LIMM) and pressure step (PPS) measure ments of the spatial polarization and electric field distributions in nonuniformly thermally poled alpha-PVDF and Teflon FEP films are repor ted. The spatial distributions obtained by the two methods are compare d over the entire thickness range, and a satisfactory agreement is fou nd. For PVDF the results of both methods are in accordance with litera ture data for similarly poled specimens of similar material, the so-ca lled 'thermal profile', a polarization peak near the anode. Furthermor e, in the LIMM experiments we found a small peak near the cathode, whi ch can be explained by a positive compensation charge layer extending approximate to 2 mu m in depth. For the first time, LIMM spectra of FE P are published. The space charge distribution in the FEP sample is ne arly homogeneous inside the sample. Near the anode side an accumulatio n of negative charges appear. Near both surfaces a positive compensati on charge was found with a thickness of similar to 1 mu m. It is demon strated that by means of our deconvolution the spatial distribution ca n be determined simultaneously with two thermal parameters, the diffus ivity of the sample material and the heat transfer coefficient between sample and sample holder.