Magnitude of Intrinsic Electrocaloric Effect in PbTiO3 at High Electric Fields

Abstract

Based on Landau-Devonshire theory, the electrothermal properties of PbTiO3bulk and film are computed near the temperatures of their phase transitions. A first-order ferroelectric to paraelectric phase transition is present in PbTiO3bulk. The coercive electric field at 700 K is about 25 MV m-1. High applied electric fields drive the transition to higher temperatures and theP−Tcurves to be continuous. For PbTiO3 film, the second-order phase transition reduces the excess entropy, and thereby the isothermal entropy change. With increasing electric field, the excess specific heat capacity becomes small, despite higher transition temperatures. The change of in-plane tensile misfit stress lowers the transition temperature. Besides, the adiabatic temperature change and the refrigerant capacity of PbTiO3bulk are 4.76 K and 94.1 kJ m-3, respectively.