Surfactant-free aqueous-phase synthesis of barium titanate nanoparticles and their growth mechanism

Current wet-chemical approaches for synthesizing small-sized and monodisperse barium titanate (BT) nanoparticles can produce BT particles of less than 100 nm. However, because of poor recyclability, they often involve complex reaction systems, expensive precursors, and environmental concerns, thus driving the need for a simple, stable method to advance the miniaturization of multilayer ceramic capacitors. Herein, we present a simplified hydrothermal synthesis using only TiO 2 and Ba(OH) 2 ·8H 2 O as raw materials in the presence of NaOH, without additional additives, to obtain irregular BT with an average size of 80 nm. Further, we systematically investigated TiO 2 precursors of varying morphologies and sizes to elucidate the hydrothermal synthesis mechanism, disproving the in situ transformation mechanism and establishing an inverse correlation between BT particle size and the specific surface area of TiO 2 . Further validation using mixed TiO 2 precursors (1:1 ratio) led to the proposal of a dissolution–precipitation nucleation mechanism in which the precursor surface area governs dissolution kinetics, subsequently determining the nucleation rate and final particle size. This study not only provides a practical and scalable synthesis route but also offers valuable insights into hydrothermal crystallization processes.