H_3BO_3をフラックス剤に用いた溶液法によるBa_2Ti_9O_<20>強誘電体材料の合成

概要

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Ba2Ti9O20 has a similar structure to Hollandite structure, and has high ionic conductivity because of its tunnel structure. It is used as electronic material in high frequency devices due to its ferroelectricity and the small temperature coefficient. The single phase of Ba2Ti9O20 is hard to obtain because only the small deviations from the required stoichiometry lead to formation of impurity phases having close chemical composition. In this study we prepared precursor of Ba2Ti9O20 by complex gellation method in which citratoperoxititanic acid tetranuclear complex was used as a Ti source. The homogeneous precursor was obtained by mixing the Ti complex, Ba(CH3COO)2, and H3BO3 (as a flux) in aqueous solution. The obtained precursor was then heat-treated at 1,273 K, which is 230 K below the temperature needed for the conventional solid-state reaction method, and the single phase of Ba2Ti9O20 was formed. The crystallite size of the prepared powder was less than 100 nm that is desirable for ferroelectric materials.
2009-04-15