Internal charge generation in polyvinylidene fluoride films during poling observed by Raman spectroscopy

The electrical degradation and charge generation in PVDF during poling has been investigated using Raman spectroscopy. Two new peaks at 1118 cm/sup -1/ and 1515 cm/sup -1/ corresponding to conjugated polyene sequences arise in the Raman spectrum after poling. In conjunction with our observation that HF gas is formed during poling at the negative electrode, a HF-unzipping chain reaction initiated by F/sup -/-ions is proposed. The large amount of HF which can be generated by this mechanism might be a source for additional ionic charges if the HF molecules dissociate into H/sup +/- and F/sup -/-ions. Thus these additional charges could lead to a complete internal polarization neutralization even if the amount of injected charges is too small for this.