Thermodynamics and fabrication of epitaxial Pb(Zr,Ti)O-3 (PZT) thin films

Abstract

Up to now, an epitaxial PZT thin him in which the tetragonal and rhombohedral phases coexist has not been successfully obtained. We have considered the reason behind the observed difficulty in the fabrication of this type of thin films and developed a new thermodynamic model for an epitaxial ferroelectric thin film under a two-dimensional compressive stress. This thermodynamic formalism predicts a shift of the morphotropic phase boundary towards the rhombohedral-phase field under the stress so as to explain the observed difficulty in the fabrication. We have experimentally proved this prediction by fabricating an epitaxially oriented tetragonal PZT thin film on MgO substrate with the target composition corresponding to the bulk MPB composition (i.e., Zr/Ti approximate to 52/48).