Formation process of BaTiO 3 particles by reaction between barium hydroxide aqueous solution and titania obtained by hyd
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Naofumi Uekawaa) Graduate School of Science and Technology, Chiba University, Inage-ku, Chiba-shi 263-8522, Japan; and Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Chiba University, Inage-ku, Chiba-shi 263-8522, Japan
Takashi Kojima Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Chiba University, Inage-ku, Chiba-shi 263-8522, Japan
Kazuyuki Kakegawa Graduate School of Science and Technology, Chiba University, Inage-ku, Chiba-shi 263-8522, Japan; and Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Chiba University, Inage-ku, Chiba-shi 263-8522, Japan (Received 14 November 2006; accepted 16 May 2007)
BaTiO3 particles were prepared by heating a suspension of titania derived from the hydrolysis of titanium isopropoxide in a barium hydroxide [Ba(OH)2] aqueous solution. Well-crystallized cubic phase BaTiO3 fine particles were obtained by heating at a temperature >328 K for 24 h. The morphology and size of the obtained particles were affected by the reaction temperature and the Ba(OH)2/titanium alkoxide molar ratio. The secondary particles with a larger size were obtained at a lower reaction temperature. The nucleation process of BaTiO3 depended on the reaction temperature. The formation mechanism of BaTiO3 and the formation kinetics were investigated by measuring the concentrations of Ba2+ ions in the solution during the heating process. The BaTiO3 particle formation occurred on the surface of the titania particles after strong adsorption of the Ba2+ ions from the solution. The experimental results showed that the heterogeneous nucleation of BaTiO3 occurred on the titania surface.
I. INTRODUCTION
Barium titanate (BaTiO3) is one of the most useful dielectric materials and has been intensively investigated. The general trends in high-tech applications require ultrafine powder with high purity and narrow size distribution.1,2 In particular, nano-sized BaTiO3 powder has become attractive and has received growing attention.3,4 Simple and effective preparation methods can also contribute to an increase in the application possibilities of barium titanate. Many solution processes used to prepare barium titanate particles at temperatures lower than 473 K have been reported. In particular, various kinds of hydrothermal
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0337 J. Mater. Res., Vol. 22, No. 9, Sep 2007
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and sol-gel processes have been investigated.5–10 Supin et al. have prepared barium titanate sols using a diolbased sol-gel route.11 Kwon et al. have made partially tetragonal barium titanate powder by using a solvothermal process with 1,4-butanediol.12 These processes can produce nano-sized barium titanate particles with uniform morphology. To control the morphology and crystallographic forms of barium titanate particles prepared by a solution process, it is of primary importance to investigate the growth mechanism.13,14 Th
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