Enhancing the electrocaloric effect in a relaxor polymer by including minor normal ferroelectric phase

Generating a large caloric effect under a low applied field is critical for realizing high performance solid state caloric cooling. Here, we report that a large enhancement in the electrocaloric response at a moderate electric field level over a relatively broad temperature range can be achieved in the relaxor poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) [P(VDF-TrFE-CFE)] polymers by including the minor normal ferroelectric phase. We show that the terpolymer of P(VDF-TrFE-CFE) 69.7/30.3/6 mol. % which contains a minor normal ferroelectric phase, under a moderate electric field of 90 MV/m, can reach an adiabatic temperature change ΔT = 11 K, compared with ΔT = 6 K of the terpolymers with a pure relaxor phase under the same field. The results reveal that the presence of the minor ferroelectric phase facilitates the polarization switch in a temperature range near the ferroelectric transition while the relaxor phase maintains a large electrocaloric effect (ECE) over a broad temperature range, resulting in a large ECE over a relatively broad temperature range in the material.