Nanoscale Structural and Chemical Properties of Antipolar Clusters in Sm-Doped BiFeO3 Ferroelectric Epitaxial Thin Films

Abstract

The local atomic structure and nanoscale chemistry of an antipolar phase in Bi0.9Sm0.1FeO3 epitaxial thin films are examined by an array of transmission electron microscopy (TEM) coupled with electron diffraction and electron energy-loss spectroscopy methods. The observations are tied to macroscopic properties of the films, namely, polarization-electric field hysteresis loops, dielectric constant-electric field hysteresis loops, and the dielectric loss. At room temperature, the local Sm deficiency was determined to destabilize the long-range ferroelectric state, resulting in the formation of local antipolar clusters with the appearance of PbZrO3-like antiparallel cation displacements, which give rise to 1/4{011} and 1/4{211} reflections as well as 1/2{321}, because of in-phase oxygen octahedral tilts. Aberration-corrected TEM analysis reveals that the antipolar structure is actually a lamellar of highly dense ferroelectric domains with alternating polarizations. With increasing temperature, a phase transi...