Synthesis of Nano-Sized BaTiO3 by solid-state reaction between $BaCO_3$ and $TiO_2$

Abstract

The recent development of thinner multilayer ceramic capacitor (MLCCs) has tremendously increased the demand for dielectric $BaTiO_3$ nanoparticles. In general, $BaTiO_3$ nanoparticles have been synthesized by wet chemical process. However, the problem of low crystalinity and difficulty in controlling the Ba/Ti ratio in these routes forced to find other ways for the synthesis of $BaTiO_3$ nanoparticles. Therefore, it is meaningful to investigate the synthesis of $BaTiO_3$ nanoparticles by conventional solid-state reaction. In the present study, formation mechanism and size control of $BaTiO_3$ in solid-state reaction between $BaCO_3$ and $TiO_2$ was systematically investigated. The formation mechanism suggested that small amount of $BaTiO_3$ is formed first at the contact surface of $BaCO_3$ and $TiO_2$ particle. The course of the reaction then was controlled by the diffusion of barium into the $TiO_2$ particle. The formation mechanism also suggested that the final $BaTiO_3$ particle size was dependent mainly on the initial $TiO_2$ particle. The milling of $BaCO_3$ particles not only accelerates the diffusion process but also ensure well mixed $BaCO_3$ and $TiO_2$ starting mixture. Therefore, controlling the size and milling condition of the starting powders could control the size of the final $BaTiO_3$. The powder mixture was calcined for different temperature and time. The phase analysis was done using X-ray powder diffractomery and particle size was confirmed by using SEM and TEM. The single phase $BaTiO_3$ was observed at temperature as low as 800℃ with average particle size of 52nm. The results are encouraging and it can be deduced that the nano-sized $BaTiO_3$ particles can be synthesized by optimizing the experimental variables in the conventional -solid-state reaction between $BaCO_3$ and $TiO_2$.