Multiple Nucleation and Crystal Growth of Barium Titanate

Crystal growth of cubic BaTiO3 in the presence of polyethylene glycol-200 (PEG-200) is investigated step by step using powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Titanium precursor Ti(OC4H9)(4) aggregates with PEG to form spherical colloidal particles at the very beginning. Multiple nucleation of BaTiO3 takes place on the surface of these colloidal particles. The nanocrystallites then self-adjust their orientations likely under dipole-dipole interaction and/or inter-crystallite interactions enhanced by surface adsorbed polymers, followed by an orientated connection and crystal extension via an Ostwald ripening process. The final BaTiO3 crystals have a novel dodecahedral morphology. The formation mechanism is proposed to be attributed to the selective adsorption of PEG molecules on the {110} crystal planes, significantly reducing the crystal growth rate on these surfaces. A kinetic model is proposed based on the calculated crystallite size using the Scherrer equation. The physical meaning of the model and a significant fake reduction of the crystallite size is discussed.