PROJECT TITLE :
Ferroelectric properties of polymeric bilayer systems
ABSTRACT:
Bilayers of VDF-TrFE ferroelectric copolymer thin films are characterised in terms of polarisation behaviour and dielectric nonlinearities. The effective properties of the ferroelectric bilayers have been investigated and compared with those of the individual layers within the stack. It's been demonstrated that the effective permittivity of the bilayer is not absolutely described by a simple series model. The remanent polarisation Pr in the bilayer shows essentially a linear decrease with temperature and reaches zero at around a hundred and twenty ° C, i.e. on top of the Curie temperatures of the two copolymers involved. The two observations are attributed to electrical bias fields within the bilayer that cause a coupling between the two layers and lead to a temperature dependence of the polarisation which is phenomenologically almost like observations in superlattices.
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