Mechanism and kinetics of the solid state reaction have. been studied with special emphasis on the effects of aggregation of reactant powder particles. Equimolar mixtures of BaCO3 and TiO2 were prepared by partial precipitation and ball milling methods using two kinds of TiO2 powders with approximately the same ele-mentary particle size in different states of aggregation.
It is shown that BaTiO3 is the only product when fine TiO2 was used but that aggregated TiO2 yielded additional products Ba2TiO4 and BaTi4O9. Disintegration of large TiO2 aggregates by ball-milling decreased the amounts of additional products, and prolonged ball-milling led to substantially the same reaction products and kinetics as those observed with fine TiO2. No single rate equation has been successfully applied to reaction isotherms obtained with different mixtures. Kinetic behavior has been interpreted in terms of the relative amounts of the reaction products as influenced by the state of aggregation of reactant powder particles.