高介电常数TiO2纳米晶的表面态研究

将钛酸四丁酯和硬脂酸在熔融状态下混合均匀后置于冷水浴中,使其凝固成凝胶,通过控制烧结过程中氧气的含量,成功地制备出粒度均匀、介电性能好的纳米晶TiO2.通过采用X射线光电子能谱和表面光电压谱对纳米晶TiO2表面状态的分析发现,材料表面存在大量的氧空位缺陷,暴露在粒子表面上的主要是一些金属Ti4+.纳米材料的这种表面状态对其极化性质具有重要的影响,使其在接近静态条件下的低频介电常数远大于常规材料的介电常数.

Surface State Studies of Nanocrystalline TiO2 with High Dielectric Constant

An appropriate amount of stearic acid was melted at 70 ℃, into which tetrabutyl titanate was added while stirring. Then the solution was cooled in cool water to form a gel. By controlling the amount of oxygen during the calcining procedure, nanocrystalline TiO2 powder with even grain size and good dielectric properties were obtained. The surface state was analyzed by means of X-ray photoelectron spectroscopy and surface photovoltage spectroscopy. The results of experiments show that the surface structure of nanocrystalline TiO2 is not integrate mainly due to the existence of oxygen cavities and most of the exposing atoms on the grain surface are Ti4+. The surface states of nanocrystalline materials put important influence on their dielectric properties and make the static state dielectric constant much bigger than that of bulk material.