POLARIZATION PROFILES IN CORONA-POLED P(VDF-TFE) COPOLYMER STUDIED BYPIEZOELECTRICALLY INDUCED PRESSURE STEP METHOD

Polarization profiles have been measured with a resolution of about 2 mu m in corona poled 95:5 P(VDF-TFE) copolymer by using the piezoelect rically induced pressure step (PPS) method. A polarization peak is obs erved near the positive side of samples poled in a negative corona by the constant current technique. The distribution of polarization is al so nonuniform in the case of a constant voltage poling at 50 MV m(-1), but profiles are rather uniform if a 100 MV m(-1) poling field is app lied at 85 degrees C. In muitilayer samples, the upper film bombarded by corona ions remains absolutely nonpolarized. Thin transition nonpol arized zones are seen near surfaces of even well polarized P(VDF-TFE). It is shown that polarization uniformity in P(VDF-TFE) is strongly af fected by injection of negative charge carriers from the virtual elect rode formed either on the surface bombarded by corona ions, or between two contacting dielectric surfaces. Our data on P(VDF-TFE) are in acc ord with those reported on other ferroelectric polymers.