How Unique are the Microstructure and the Electrical Properties of Nanocrystalline Ceramics?

摘要

A literature overvie on microstructural and electrical properties of nanocrystalline ceramics is given. Space charge effects in nanosystems, especially thin-films nd colloidal particles, are discussed from a theoreticla pointof view. Some common features ofnanocrystalline ceramics are pointed out: nanoparticles present few extended lattice imperfections and the densification process beings at distinctly lower temperatures than that of coarse-grained ceramics. A significant decrease ofgrain boundary resistance occures due to grain-size dependent dopant segregation, which leads also to an important increase of the apparent solubility of dopants in nanocrystalline materials. A number ofstuides confirm the theoretically expected reduction of the poitn defect formation enthalpy at interface sites, giving rise to significantly larger non-stoichiometry an electronic conductivity of nanocrystalline materials. Increased ionic conductivity has been found only in a limited number of cases, some of which remain controversial.