Preparation of BaTiO₃ by homogeneous precipitation

Three different methods are studied for the preparation of fine-grained BaTiO3 by homogeneous precipitation: (1)Hydrolysis of barium and titanium alkoxide precursors, in which the required water is generated by an esterification reaction; (2)Precipitation of a barium¿titanium complex as a result of thermal decomposition of Ba-EDTA; (3)Precipitation of a barium and titanium complex by the increase of pH caused by the hydrolysis of urea. The properties of powders, prepared via these methods, and their sintering behaviour are as follows: (1)The esterification method results in a powder with medium average aggregate size of about 3 ¿m and a sintered density of 90% which is higher than the value obtained with the other precipitation methods. The considerable differences, in hydrolysis rate between the barium and titanium precursors used, lead to second phase formation; (2)The complexation method gives the most promising results; 1 ¿m sized spherical aggregates were obtained which consist of smaller particles. Sintered densities obtained were up to 88% and the method can be optimised further to obtain values in excess of 95%; (3)The urea method results in large irregular aggregates and is found to be unsuitable for the preparation of BaTiO3 ceramics.