Orientation dependence of the electrocaloric effect of ferroelectric bilayer thin films

An analytical thermodynamic theory is applied to investigate the electrocaloric effect of ferroelectric BaTiO₃/SrTiO₃ bilayer thin films with different orientations at room temperature. Theoretical analysis indicates that the strong electrostatic coupling between the layers results in the suppression of ferroelectricity at a critical relative thickness which occurs approximately at 50%, 23%, and 12% of SrTiO₃ fraction in the (001), (110), and (111) bilayer thin films, respectively. The ferroelectric bilayer thin films are respected to have the largest electrocaloric effect at this critical relative thickness. Moreover, the electrocaloric effect strongly depends on the orientation and the (110) oriented bilayer thin films have the largest electrocaloric effect. Consequently, control of the orientation and the relative thickness of SrTiO₃ layer can be used to adjust the electrocaloric effect of ferroelectric bilayer thin films, which may provide the potential for practical application in refrigeration devices.