Phase Evolution and Nucleus Growth Observation of Solid-State BaTiO 3 Powder Prepared by High-Energy Bead Milling for Raw Material Mixing

• Published in: Japanese Journal of Applied Physics 2011-09, Vol.50 (9R), p.91502
• Main Authors: Lee, Ting-Tai, Huang, Chi-Yuen, Chang, Che-Yuan, Lin, Shih-Pin, Su, Che-Yi, Lee, Chun-Te, Fujimoto, Masayuki
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.50.091502

The solid-state synthesis, phase evolution, and nucleus growth of the barium titanate (BaTiO 3 , BT) powder were investigated in this study. Rapid nucleus growth and precursor phase formation of BT were observed at a relatively low temperature of 600 °C by mixing BaCO 3 (2 m 2 /g) and TiO 2 (7 m 2 /g) with a high-energy bead mill. The decomposition of BaCO 3 and the formation of the Ba 2 TiO 4 phase were identified by transmission electron microscopy (TEM). On the basis of this observation, the weight loss observed at 600 °C in the derivative thermogravimetry (DTG) curve could also be explained. Furthermore, with increasing calcination temperature, single cubic BT with less than 80 nm fine nuclei/crystallites was observed at 900 °C, and tetragonal BT ( c / a > 1.008) with an average particle size of 0.4 µm was obtained at 1000 °C. With regard to the dielectric properties of sintered ceramics, the relative permittivity (ε r ) increased with calcination temperature, and the Curie point also shifted to a progressively higher temperature. However, BT nucleus samples (with low calcination temperatures of 800 and 900 °C) could not satisfy the X7R requirement (Electric Industries Association Standard, the tolerance of capacitance from -55 to +125 °C is ±15%) until calcination temperature increased to 1000 °C.