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

Abstract

Various processes of coprecipitation or crystallization of inorganicsalts of barium and titanium from homogeneous solutions were studiedin this work. In particular, barium hydroxide and barium chloridesalt as well as titanium tetrachloride were used as the startingmaterials for dielectric-tuning homogeneous precipitation in mixedsolvents of isopropanol and water. Hydroxypropylcellulose was used asa steric dispersant. Evaluations of size, shape, and composition ofsynthesized particles were made using scanning electron microscopy,high-temperature X-ray diffractometry, and differential thermalanalysis. Results show that salt concentration, pH, and reaction timeare important in determining the morphology and composition of thefinal powder. The titania particles from dielectric-tuningprecipitation are perfect microspheres with narrow size distribution(near monodispersed), while the particles from barium salts areflake-like, irregular in shape and size. Instead of particlescontaining uniform compositions of barium and titanium compounds,dielectric-tuning coprecipitation yielded powders of two separatedphases, i.e., monodispersed titania microspheres (∼1 μm) coated onbarium chloride salt flakes. Titanium-rich barium titanate wasobtained after calcination of coprecipitated powders. However,preliminary results show that the titania particles obtained bydielectric-tuning precipitation can be hydrothermally converted toBaTiO₃ particles that are fully crystallized after calcination above950°C.