Controlled hydrothermal synthesis of highly crystalline tetragonal BaTiO3 nanocrystals with uniform size distribution

Highly dispersed tetragonal phase BaTiO₃ nanoparticles were synthesized via a hydrothermal method. The effects of TiO₂ precursor and hydrothermal media on the phase transformation and microstructure of BaTiO₃ nanocrystals were investigated. Additionally, the time-dependent evolution of nucleation and crystal growth was elucidated. A key influencing factor of this method is the use of a well-crystallized TiO₂ as the precursor, combined with ammonia-based reaction media; this combination not only promotes nucleation but also inhibits OH defect formation during crystal growth. Consequently, superior tetragonality and narrow particle size distribution of BaTiO₃ nanoparticles can be achieved. Furthermore, atomic-scale internal and surface structure were investigated using high-angle annular dark field scanning transmission electron microscopy. Ferroelectric and piezoelectric properties of the prepared samples were examined based on their polarization characteristics using piezoelectric responsive force microscopy, further confirming the high tetragonality of the as-prepared BaTiO₃ nanoparticles.