Polarization profiles in corona poled P(VDF-TFE) copolymer studied by piezoelectrically induced pressure step method

Polarization profiles have been measured with a resolution of about in corona poled 95:5 P(VDF-TFE) copolymer by using the piezoelectrically induced pressure step (PPS) method. A polarization peak is observed near the positive side of samples poled in a negative corona by the constant current technique. The distribution of polarization is also nonuniform in the case of a constant voltage poling at , but profiles are rather uniform if a poling field is applied at . In multilayer samples, the upper film bombarded by corona ions remains absolutely nonpolarized. Thin transition nonpolarized zones are seen near surfaces of even well polarized P(VDF-TFE). It is shown that polarization uniformity in P(VDF-TFE) is strongly affected by injection of negative charge carriers from the virtual electrode formed either on the surface bombarded by corona ions, or between two contacting dielectric surfaces. Our data on P(VDF-TFE) are in accord with those reported on other ferroelectric polymers.