Synthesis and growth mechanism of donut-like lead titanate particles by hydrothermal method

Tetragonal perovskite structure PbTiO3 donut-like particles have been synthesized by a hydrothermal method in strong alkaline environment using lead nitrate (Pb(NO3)2) as the lead source and TiCl4 as the titanium source. The as-prepared particles were characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM), and it was indicated that the phase composition and particles shapes were influenced by the reaction temperature and reaction time. Based on the morphologies and phase evolutions as a function of reaction temperature or reaction time, a mechanism for the growth of the donut-like PbTiO3 particles was proposed to involve nucleation, agglomeration, phase in situ conversion, dissolution, and recrystallization. The spherical particles were formed by primary nucleation of PbTi0.8O2.6 followed by agglomeration into platelets. Then, the platelet PbTi0.8O2.6 particles in situ converted into Pb2Ti2O6 particles. Under the effects of temperature, pressure (autogenous pressure), and high solution pH value, the platelet Pb2Ti2O6 particles dissolved from its center of surface and recrystallized to form PbTiO3 nano-particles which adhered to its edges. Finally, the monocrystal donut-like PbTiO3 particles were formed as the dissolution of Pb2Ti2O6 particles completed.