The role of material chemistry in processing BaTiO ₃ in aqueous suspensions

The application of material chemistry concepts to processing powder suspensions including solution thermodynamics will be demonstrated on several material systems, notably the complex metal oxide, barium titanate, in aqueous environments. After a discussion of the relevant thermodynamic and kinetic issues for fine particles in liquids, various characterization approaches to understand and control the behavior of powders in liquids will be discussed. Various colloidal characterization techniques, high-resolution TEM, and chemical analyses of both the solution and solid exposed to solution have been used to study the nature of the chemical reactions and subsequent altered surface layers in the barium titanate-water system. The key factor in developing an effective aqueous processing scheme for any water sensitive material (and all metal oxides are water sensitive) in aqueous suspension, is recognition that deleterious surface hydrolysis reactions must be prevented. It is shown that local chemical inhomogeneities play a role in abnormal grain growth in the barium titanate system exposed to aqueous environments, but can be controlled with appropriate chemical passivation approaches. The success of a passivation-dispersion approach in the aqueous processing of these materials will be discussed as well as the implementation of the general concept of material chemistry approaches to the aqueous processing of other water sensitive materials.