Ind. Eng. Chem. Res. 2003, 42, 473-483
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Hydrothermal Synthesis of Barium Titanate Huei-Jyh Chen and Yu-Wen Chen* Department of Chemical Engineering, National Central University, Chungli 32054, Taiwan
Barium titanate fine particles were prepared by hydrothermal synthesis. The synthesis was preformed at a temperature between 75 and 180 °C and for 10 min to 96 h. The reactions were carried out in a strong alkaline solution. Ba(OH)2‚8H2O was used as the Ba-precursor material. Various Ti precursors were used to investigate their effects on the properties of BaTiO3. The BaTiO3 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, nitrogen sorption, and differential scanning calorimetry. XRD showed that the as-synthesized BaTiO3 powders have the BaTiO3 structure. The particle size of the Ti precursor has a strong influence on the size and morphology of barium titanate. The particle size of BaTiO3 was the largest when synthesized at 120 °C for 24 h by using anatase TiO2 (Merck) precursor. The particle size was about 0.1 µm when using TiO2 (70% anatase and 30% rutile, Degussa P25) or Ti(OH)4 as the precursor. The BaTiO3 powder was a porous structure when using Ti(OH)4 as the precursor. In addition, the particle size and morphology were dependent on the synthesis temperature. At 85 °C, the morphology of the powder was small crystal and an agglomerate of clusters. At 180 °C, the morphology of the powder was large (∼130 nm), uniform, and nearly monodisperse particles. Extending the synthesis time has no significant influence on the size and morphology. 1. Introduction Barium titanate (BaTiO3), a perovskite structure, has been widely investigated because of its dielectric and ferroelectric properties. Conventional synthesis of barium titanate is by the solid-state reaction. Solid mixtures of barium carbonate and titanium dioxide are prepared at high temperature (∼1100 °C) or by calcination of chemically derived intermediates. The powders thus produced are often low in purity and are composed of large and nonuniform particles. Recent advances in microelectronic and communication industries have led to the miniaturization of multilayer ceramic chip capacitors (MLCC). At the same time, performance requirements have increased: higher mechanical strength, higher reliability, and lower cost. To meet these advanced performance features, manufactures need to fabricate MLCC with uniform, ultrathin ceramic active layers with a
