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.