Linear and Nonlinear Dielectric Response of VDF60/Tr40 Copolymer in the Vicinity of Ferroelectric Phase Transition

The effect of the bias electric field E= (0–10 kV/cm) on the dielectric properties of the VDF60/Tr40 copolymer was studied in the temperature range of 20–110°C. It was found that the dielectric nonlinearity Δε is negative in the polar phase and becomes positive above the Curie temperature (TC). The increase in TC under the field E= is not uniform. At E= < Ec (Ec is the threshold field), the Curie temperature is practically independent of E=. At E= > Ec, an increase in TC is observed. The presence of the threshold field indicates the existence of sources of random electric fields in the material under study. It is suggested that they are responsible for the smearing of the ferroelectric phase transition.