Synthesis of Ba₂Ti₉O₂₀ ferroelectrics by solution method with H₃BO₃ as a flux

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(CH ₃COO)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.