Solid State Synthesis of 200nm-Sized BaTiO_3 Dielectric for Ultra High Capacitance MLCC

摘要

BaTiO_3 dielectric with deagglomerated finer grain size as well as higher tetragonality was required in order to produce multilayer ceramic capacitor (MLCC) of high capacitance with small size. In this study, fine-grained BT dielectric powder for MLCC of very thin dielectric layer less than lum was synthesized by solid-state reaction using fine-milled BaCO_3 and nanocrystalline TiO_2 powder with high specific surface area. A high energy milling in aqueous slurry was applied and the particle size of BaCO_3 powder decreased significantly and its morphology changed from needle to round by pre-milling before mixing with TiO_2. BaTiO_3 powder with the tetragonality of 1.0097, the average particle size of 213 nm and along with the specific surface area of 6.30 m~2/g were acquired after heat treatment at 985℃ for 2 h. Long time milling of BaCO_3 and adoption of nanocrystalline anatase-rich TiO_2 were effective in decreasing the reaction temperature and in increasing the tetragonality (=c/a). Dielectric sample made of this solid-state reacted BaTiO_3 showed higher dielectric constant than that from hydrothermal powder.