The electric moment contribution to the piezoelectricity of PVDF

Basically the piezoelectric constant is composed of two contributions, i.e. of mechanical load-induced changes of the sample electric moment at fixed sample shape (`moment term´) and of mechanical load induced changes of the sample shape at fixed sample electric moment (`shape term´). In the present paper, the contribution of the material´s permittivity to the moment terms of the hydrostatic piezoelectric coefficients of unoriented polarized PVDF/PMMA blends are calculated and compared with the experimental values. It must be concluded from the results that the polarized domains behave as elongated particles which are oriented parallel to the polarization direction although the supermolecular structure is isotropic. Several possible origins of this observation are presented and discussed