ALKOXIDE HYDROXIDE ROUTE TO SYNTHESIZE BATIO3-BASED POWDERS

When preparing homogeneous, fine barium titanate powders, the major difficulty is to avoid the spontaneous self‐condensation between the Ti‐OH groups. In the usual way of preparing fine barium titanate powders, chelating agents (citrate, oxalate) or simply unidentate ligands (alkoxy or carboxyl groups) are used to complex titanium atoms. Another way is to mix barium and titanium precursors in a strongly basic medium. The condensation between the Ti(OH)2‐6Ba2+ species directly gives the perovskite compound. Using an alkoxide‐hydroxide route, a homogeneous Ba‐Ti solution was prepared that completely advanced by condensation between the Ti(OH)2‐6Ba2+ species and led to a controlled‐stoichiometry powder. Concerning pure barium titanate, dried powders exhibited the cubic perovskite structure, and a direct sintering at 1150°C, without calcination, led to highly dense BaTiO3 bodies with fine‐grained uniform microstructure (1 μm) that exhibited a high permittivity value at room temperature (K= 5400). The alkoxide‐hydroxide method was also used to prepare dense alkaline‐earth perovskite ceramics with complex compositions. Copyright © 1990, Wiley Blackwell. All rights reserved