Barium titanate nanoparticle self-organization in an external electric field

Abstract

We describe the formation of BaTiO3 superstructures from precursor nanoparticles and the use of ferroelectric properties to trigger a hierarchical growth mechanism. Without specific treatment, the precursor nanoparticles comprise of ferroelectric domains that are oriented randomly (domains of the same spontaneous polarisation). However, using an external electric field the ferroelectric polarization of all domains can be oriented into the same direction and an enduring microscopic dipole results for each precursor nanoparticle. Self-organization of the polarized BaTiO3 nanoparticles to dumbbell- and cross-shaped superstructures was observed as a combined result of nanoparticle alignment by the electric field and crystallographic fusion of the nanoparticles under defined coincidence angles following an oriented attachment process. These structures were characterized by electron microscopy and the nanoparticle superstructure formation guided by electrical dipole fields is explained by molecular modeling. The combination of an orienting physical field with the crystallographic lock in dictated by the crystal lattice is a new mechanism for the guided self-organization of nanoparticles.