Homogeneous (co)precipitation of inorganic salts for synthesis of monodispersed barium titanate particles

Various processes of coprecipitation or crystallization of inorganic salts of barium and titanium from homogeneous solutions were studied in this work. In particular, barium hydroxide and barium chloride salt as well as titanium tetrachloride were used as the starting materials for dielectric-tuning homogeneous precipitation in mixed solvents of isopropanol and water. Hydroxypropylcellulose was used as a steric dispersant. Evaluations of size, shape, and composition of synthesized particles were made using scanning electron microscopy, high-temperature X-ray diffractometry, and differential thermal analysis. Results show that salt concentration, pH, and reaction time are important in determining the morphology and composition of the final powder. The titania particles from dielectric-tuning precipitation are perfect microspheres with narrow size distribution (near monodispersed), while the particles from barium salts are flake-like, irregular in shape and size. Instead of particles containing uniform compositions of barium and titanium compounds, dielectric-tuning coprecipitation yielded powders of two separated phases, i.e., monodispersed titania microspheres (similar to 1 mu m) coated on barium chloride salt flakes. Titanium-rich barium titanate was obtained after calcination of coprecipitated powders. However, preliminary results show that the titania particles obtained by dielectric-tuning precipitation can be hydrothermally converted to BaTiO3 particles that are fully crystallized after calcination above 950 degrees C. (C) 2000 Kluwer Academic Publishers.