Synthesis and characteristics of near-stoichiometric barium titanate powder by low temperature hydrothermal reaction using titanium tetra(methoxyethoxide)

Near-stoichiometric BaTiO₃ powders with ultrafine particle size and high crystallinity were prepared by low temperature hydrothermal reaction of Ba(OAc)₂ and Ti(OCH₂CH₂OCH₃)₄. BaTiO₃ particles were synthesized in the spherical, metastable cubic crystalline grains with size distribution between 60-90 nm in diameter. Ultrafine particle size was resulted from the control of the hydration rate and the decrease of Ti-O-Ti cross-linking extent of titanium precursor, Ti(OCH₂CH₂OCH₃)₄, which gives electronic, steric, and weakly chelating effect to titanium ion. Increasing the Ba/Ti mole ratio in reactant could not overcome the notorious Ba-deficiency but, improved stoichiometry and produced finer and less agglomerated particles. Interestingly, adding a slight pressure to autogeneous hydrothermal condition (total 4-10 atm) has yielded near-stoichiometric, highly crystalline, and less agglomerated BaTiO₃ particles. These particles, which were in metastable cubic form as synthesized, initiated phasetransition to tetragonal form by calcination at below 400 °C.