Effects of surface state of nanocrystal PbTiO3 on their dielectric properties

Nanocrystalline PbTiO3 powder was obtained by melting appropriate amount of stearic acid at 70 degreesC, into which tetrabutyl titanate and lead acetate were added while stirring. Then the solution was cooled in cool water to form a gel and the gel was calcined at different temperatures. The products were characterized by X-ray powder diffraction and infrared spectra analysis. The surface state was analyzed by means of X-ray photoelectron spectroscopy and surface photovoltage spectroscopy (SPS). The results show that the surface structure of nanocrystalline PbTiO3 is not integrate mainly due to the existence of oxygen cavities and most of the exposing atoms on the grain surface are metal ions. With the reducing of grain size, the oxygen cavity defect increases, the photovoltage effect on the surface enhances and the width of SPS becomes wider. The surface states of nanocrystalline materials have important influence on their dielectric properties and make the static state dielectric constant much bigger than that of bulk material.