Interpretation of hydrothermal crystallization of fine BaTiO3 powders

In the preparation of fine BaTiO3 powders under hydrothermal conditions, th e reaction mechanism was interpreted through solid-state kinetic analysis o f the Johnson-Mehl-Avrami plot. In this experiment reactants were dissolved and consumed to spherical particles of 50 nms from aggregation of several nanometer-sized particles. The particulate formation of BaTiO3 underwent a 1st-order hydrolysis-condensation reaction with phase-boundary transition i n the early stage of the reaction regardless of the initial concentration o f the feedstock. However, as the concentration of nutrients was reduced, di ssolution followed by precipitation became dominant, and a diffusion-contro lled reaction proceeded. When the concentration of nutrients was reduced to an extent that was not high enough to sustain supersaturation, the reactio n was controlled by solidification for encapsulation of aggregated particle s, inside of which the diffusion-controlled reaction slowly proceeded.