Generation of unagglomerated, dense, BaTiO3 particles by flame-spray pyrolysis

Fine particles of dense, high-purity crystalline BaTiO3 were produced by flame-spray pyrolysis. A 0.5-M (Ba:Ti = 1:1) solution of barium acetate, titanium lactate, and water was aerosolized using an ultrasonic generator, and the droplets were delivered into the core of an annular diffusion flame (H-2/air) reactor. For all investigated temperatures [similar to 1,000-similar to 2,000 degrees C adiabatic], the generated powders were chemically pure, crystalline (primarily tetragonal phase with hexagonal and cubic polymorphs), and unagglomerated. At a low-flame temperature (similar to 1,000 degrees C ad.), the particles produced were hollow and irregularly shaped. Particles produced at higher flame temperatures (> similar to 1,500 degrees C ad.) were dense and homogeneous. Particles showed a transition from a nonspherical porous morphology to a spherical dense morphology with increasing temperature. By increasing residence time, the temperature at which particles became spherical and dense was reduced. Flame-spray pyrolysis provides a useful method for forming dense particles of high melting point materials by aerosol-phase densification.