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 titan ium tetrachloride were used as the starting materials for dielectric-tuning homogeneous precipitation in mixed solvents of isopropanol and water. Hydr oxypropylcellulose was used as a steric dispersant. Evaluations of size, sh ape, and composition of synthesized particles were made using scanning elec tron microscopy, high-temperature X-ray diffractometry, and differential th ermal analysis. Results show that salt concentration, pH, and reaction time are important in determining the morphology and composition of the final p owder. The titania particles from dielectric-tuning precipitation are perfe ct microspheres with narrow size distribution (near monodispersed), while t he particles from barium salts are flake-like, irregular in shape and size. Instead of particles containing uniform compositions of barium and titaniu m compounds, dielectric-tuning coprecipitation yielded powders of two separ ated phases, i.e., monodispersed titania microspheres (similar to 1 mu m) c oated on barium chloride salt flakes. Titanium-rich barium titanate was obt ained after calcination of coprecipitated powders. However, preliminary res ults show that the titania particles obtained by dielectric-tuning precipit ation can be hydrothermally converted to BaTiO3 particles that are fully cr ystallized after calcination above 950 degrees C. (C) 2000 Kluwer Academic Publishers.