Thermodynamics
Electrocaloric Materials

To define the electrocaloric effect, we need to recall a few elements of classical thermodynamics. The electrocaloric effect cannot be dissociated from the pyroelectric effect, of which it is the symmetrical (in the sense of electrical/thermal energy conversion).

The fundamental quantities of pyroelectricity are, for the electrical part, the field E_k and the electrical displacement D_k ("k" index from 1 to 3 translating the three possible directions for the electrical quantities), and, for the thermal part, the temperature T and the entropy S. Assuming that these four quantities are state functions, it is possible to formalize the electrocaloric effect based on the development of the free enthalpy or Gibbs energy G of the system...