TEM Characterization and Raman Spectra of Hydrothermal BaTiO3 Nanoparticles

Microstructures of BaTiO₃ (BT) nanoparticles synthesized by hydrothermal process, were investigated by transmission electron microscopy (TEM) and Raman spectra. TEM images showed that BT nanoparticles synthesized at high Ba/Ti molar ratios in the precursors had large particle sizes and cubic morphology. Small faceted-particles were observed in the BT powders synthesized by using ethylene glycol (EG) as solvent, in comparison to reactive medium of pure water or water-EG mixed solution. X-ray diffraction and selected area electron diffraction revealed that the as-produced BT nanoparticles exhibited a room temperature-stabilized cubic structure, whereas Raman spectra indicated a tetragonal phase BT existing in the produced nanoparticles, which is not the dominant phase due to the weak characteristic peak of tetragonal structure at 305 cm^?1. HRTEM images demonstrated that the BT nanoparticles with either cubic or rectangular shapes, were bounded by their {100} facets, and a terrace-ledge-kink surface structure was frequently observed at the edges of rough nanoparticles. Surface steps lying on the {100} planes were clearly observed. However, in the spherical nanoparticles, their surface edges were very smooth, and no surface steps were observed.