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Effect of Space Charge on Polarization Reversal Currents in a Vinylidene Fluoride/Trifluoroethylene Copolymer
Author(s) -
Guy Ian L.,
DasGupta Dilip K.
Publication year - 1992
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.4990270305
Subject(s) - space charge , poling , materials science , polyvinylidene fluoride , copolymer , polarity reversal , polarization (electrochemistry) , ferroelectricity , ferroelectric polymers , electric field , tetrafluoroethylene , polymer , amorphous solid , pyroelectricity , condensed matter physics , fluoride , asymmetry , polymer chemistry , voltage , dielectric , physics , composite material , chemistry , optoelectronics , electron , organic chemistry , inorganic chemistry , quantum mechanics
Polyvinylidene fluoride and its copolymers with trifluoroethylene and tetrafluoroethylene are ferroelectric. Reversal of polarization in these polymers is known to occur by a rotation of the polar molecular chains, in response to an externally applied electric field. Recent evidence suggests that the dynamics of polarization reversal can be affected by movement of space charges in the amorphous phase of the polymers. If a 75/25 mol.% vinylidene fluoride/trifluoro‐ethylene (VF 2 /VF 3 ) copolymer is poled at elevated temperature, the subsequent polarization reversal currents show large asymmetry and significant shifts in successive reversals. The field required to reverse the polarization in such high‐temperature poled material is significantly larger than the normal coercive field. The asymmetry in the reversal currents is consistent with the presence of local fields within the polymer, generated by space charge which accumulates during the poling process. The subsequent movement of this space charge causes the shift in successive reversal currents. The variation of reversal current with temperature indicates that the movement of space charge within the copolymer is a thermally activated process.