IMF2017

In an aged ferroelectric sample, a pinched hysteresis loop is present, the origin of which can be interpreted by the presence of the defect dipoles. The aging behavior influences multiple materials properties. To the best knowledge of the authors, the influence of aging on the electrocaloric effect (ECE) is not investigated. Using a direct calculation approach based on Monte Carlo simulation with a Landau-Ginzburg type Hamiltonian, the ECE of aged BaTiO₃ is evaluated. In the simulation setup, the defect dipoles with two opposite directions are placed perpendicular to the external field, which induces a perpendicular internal field. This leads to the phenomena that the characteristic pinched hysteresis loop appears below the Curie temperature T_C, and disappears above T_C. Below T_C, with the field applied the domain configuration is disordered close to the defect dipoles. After field removal, in the vicinity of the defect dipoles, the domain configuration becomes more ordered than with applied field, which leads to the decrease of the configurational entropy. Thus, the positive temperature change under field removal, i.e., the negative ECE, is observed. Above T_C, the initial configurational entropy with field applied is bigger when introducing defect dipoles. After field removal, the final configuration entropy in the case with defect dipoles is similar to the defect-free case. Therefore, the increase of the configurational entropy is smaller in the case with defect dipoles, which leads to the degeneration of the positive ECE. Simulation results will be compared with experimental data.