Influence of surface state on the dielectric properties of nanocrystalline BaTiO3

Nanocrystalline BaTiO3 with even grain size was synthesized by a stearic acid gel method and the relationship between the surface state and the dielectric property was investigated. The products were characterized by X-ray powder diffraction, infrared spectra analysis and transmission electron microscope. The surface state was analyzed by means of X-ray photoelectron spectroscopy. The results show that the surface structure of nanocrystalline BaTiO3 is not integrated mainly due to the existence of oxygen cavities, and most of the exposed atoms on the grain surface are metal ions. With the decrease of the grain size, the content of oxygen cavity defect increases and the polarization is enhanced. The surface states of nanocrystalline materials put an important influence on their dielectric properties and make the static state dielectric constant much bigger than that of bulk material.