Electrocaloric Effect (ECE) in Ferroelectric Polymer Films

The electrocaloric effect (ECE) is the change in temperature and/or entropy of a dielectric material due to the electric field induced change of dipolar states. Electrocaloric effect in dielectrics is directly related to the polarization changes under electric field.[1-3,6] Hence a large polarization change is highly desirable in order to achieve a large ECE which renders the ferroelectric materials the primary candidates for developing materials with large ECE. Figure 1 illustrates schematically the ECE in a dipolar material. Application of an electric field to the material causes partial alignment of dipoles and consequently a reduction of entropy of the dipolar system. In an isothermal condition, the dipolar material rejects heat Q=TΔS to the surrounding, where T is the temperature and ΔS is the isothermal entropy change. Or in an adiabatic process, to keep the total entropy of the material constant, the temperature of the dielectric is increased by ΔT, the adiabatic temperature change which is related to the Q = CΔT where C is specific heat capacity of the dielectric. In a reverse process, as the applied electric field is reduced to zero and the dipoles return to the less ordered state (or disordered state), an increase in the entropy of dipolar system occurs and under an isothermal condition, the dielectric will absorb heat Q from the surrounding.