The origin of piezoelectricity in polymeric materials

The origin of piezoelectricity and related phenomena in poled polymeric materials is reexamined. It is suggested that in most cases the result of poling is the setting up of stable interfaces between polarized domains and conductive amorphous phases. These interfaces have double layer properties and high local fields are established in them while the bulk of the material has a much lower field. It will be shown that these regions of high electrical stress are the piezoelectric elements and control the acoustic response of the material. As such they are examples of a universal electrostrictive phenomenon associated with all interfaces. The microscopic piezoelectric mechanisms operating after poling in the newer cellular-foamed polymer electrets are considered in the light of the above.