Structural evolution and characterization of BaTiO3 nanoparticles synthesized from polymeric precursor

We synthesized barium titanate (BaTiO3) particles by heat-treating the polymeric precursors in air at 500-900 degrees C and proposed a model for the BaTiO3 formation from the polymeric precursors. The model contained a series of steps such as the transformation of the precursor to amorphous barium titanate, three-dimensional nucleation and growth, and solid-state reaction. We investigated the crystal structure of the particles (20 nm in size), processed at 600 degrees C, using X-ray powder diffractometry (XRD) and Raman spectroscopy. The XRD measurement indicated formation of cubic BaTiO3, and the Raman spectrum indicated that the particles of 20 nm size might have had a tetragonal symmetry. For the particles heated at 500 degrees C, XRD and Raman spectroscopy data suggested the presence of a high-temperature hexagonal phase at room temperature. High-resolution transmission electron microscopy indicated that the peaks that were ascribed to the above phase, in the Raman and XRD spectra, may originate from (111) planar defects in the particles. (C) 1998 Elsevier Science Ltd. All rights reserved.