Particle Coarsening II: Growth Kinetics of Hydrothermal BaTiO₃

Coarsening of barium titanate (BaTiO 3 ) particles under hydrothermal conditions was investigated theoretically and experimentally. A detailed model, in which coarsening is assumed to be controlled by a reversible interface reaction, is presented and discussed. The model predicts a linear growth law R − R 0 = Kt in the early stage of coarsening. This result is supported by the experimental data collected for conventional and microwave-assisted hydrothermal syntheses at two different temperatures. The growth constant K corresponds to a nonlinear combination of thermodynamic and kinetic parameters. Under microwave irradiation, the growth rate was found to be 1 order of magnitude larger than in a conventional hydrothermal process. The predicted variation of the growth kinetics, from linear to parabolic, was observed experimentally at long reaction times.