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Abstract
The electrocaloric (EC) effect in normal ferroelectric copolymer P(VDF-TrFE) and in relaxor terpolymer P(VDF-TrFE-CFE) is described in the framework of a phenomenological appoach. The change of the dipolar entropy in the copolymer, derived earlier from dielectric measurements by means of the Maxwell relation, is analyzed in terms of the mean field expression for entropy, and is shown to be consistent with the dielectric data. In the terpolymer case, the entropy change determined recently by direct (EC) measurements is found to be in qualitative agreement with the predictions of the mesoscopic spherical model of relaxor ferroelectrics.
Acknowledgments
This work was supported by the Slovenian Research Agency through Grants P1-0044, P1-0125, P2-0105, J1-0155, and J1-2015. Research at the Pennsylvania State University was supported by the US DoE, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award No. DE-FG02-07ER46410.