Supercritical hydrothermal synthesis of barium titanate nanocrystals: Mechanisms of key parameters and crystallization kinetics

Multilayer ceramic capacitors are crucial fundamental components in the electronics industry. Their high-performance requirements necessitate that barium titanate, as a dielectric material, possesses nanoscale size, high crystallinity, high dispersion, and a narrow particle size distribution. Traditional synthesis methods struggle to simultaneously achieve these properties, limiting the further miniaturization and increased capacitance of multilayer ceramic capacitors. Due to the extremely low dielectric constant, high diffusion coefficient, and near-zero surface tension under high temperature and pressure, supercritical hydrothermal synthesis enables millisecond-level rapid nucleation and precise crystallization control. This study systematically investigates the impact of key parameters in supercritical hydrothermal synthesis of nanocrystalline BaTiO₃ on product characteristics, reveals the mechanisms of each parameter, and establishes a quantitative crystallization kinetics model. The results show that temperature and pressure primarily regulate crystallinity, particle size and tetragonal phase transition; reaction time dominates particle size and dispersion; and alkaline conditions are the chemical prerequisite for driving selective crystallization of the perovskite phase. By controlling the hydrolysis-complexation form of Ti species, the transformation from amorphous to highly ordered nanocrystals is achieved. The research provides a theoretical foundation for predicting the correlation between process parameters and product performance, supporting the controllable scaling-up of the supercritical hydrothermal synthesis process, and offering important guidance for the preparation of high-performance multilayer ceramic capacitors dielectric materials.