Polarization rotation and piezoelectricity of electric field-induced monoclinic and triclinic structures in strained PbTiO3

Abstract

Electric field-induced polarization rotation, phase changes, and piezoelectric effect of strained PbTiO3 films have been investigated using a phenomenological approach. Low-symmetry monoclinic and triclinic structures have been induced, and the type of intermediate phases during polarization rotation is closely related to both the initial state at zero electric field and anisotropy of the in-plane strain. The monoclinic MC and triclinic structures in general may exhibit high shear piezoelectric coefficient d35 and sometimes also remarkable enhancement of longitudinal piezoelectric coefficient d33 around the transition point. High piezoelectric activity and low critical field have been found in epitaxial PbTiO3 with equal but opposite in-plane strain where monoclinic MC is the only intermediate phase on the polarization path. The present results suggest that anisotropy of epitaxial strain may have significant impact on polarization rotation behavior and electromechanical coupling of ferroelectric thin films.