BaTiO3 particle formation mechanism under hydrothermal conditions

Solid-state kinetic analysis by the Johnson-IMehl-Avrami plot was introduce d to understand the reaction mechanism of fine BaTiO3 powders prepared unde r hydrothermal conditions. In the experiment reactants were dissolved and c onsumed to spherical particles of 50 nm from aggregation of several nanomet er-sized particles. The particulate formation of BaTiO3 underwent Ist-order hydrolysis-condensation reaction with phase-boundary transition in the ear ly stage of the reaction regardless of the initial concentration of the fee dstock. However, as the concentration of nutrients reduced, dissolution fol lowed by precipitation became dominant, and a diffusion-controlled reaction proceeded. When the concentration of nutrients reduced to an extent that w as not high enough to sustain supersaturation, the reaction was controlled by solidification for encapsulation of aggregated particles, inside of whic h the diffusion-controlled reaction slowly proceeded.