Nano size BaTiO3 powder coated with silica

Physical characteristics of silica-coated BaTiO3 powders were studied. BaTiO3 powders (∼30 nm) were coated with TEOS and ethanol, and KOH solution was used as a catalyst. As the silica content was increased, silica coating changed the surface state of BaTiO3 powders and improved dispersion of the powder. Effects of silica coating on the sintering behavior of BaTiO3 were investigated using TMA. The specimen coated with 5.0 wt.% silica showed the maximum shrinkage of 25.5%, whereas the shrinkage of the uncoated BaTiO3 was 20.4%. At the silica content greater than 1.0 wt.%, the characteristic X-ray peaks of fresnoite (Ba2TiSi2O8) were observed. The specimen coated with silica less than 1.0 wt.% completed densification below 1250 °C, whereas the specimen with greater than 3.0 wt.% gave rise to swelling.