Role of grain boundaries on the electrical conductivity of nanophase zinc oxide

The grain boundaries of nanostructured materials play an important role in their transport properties. The impedance spectroscopy can effectively be used to study the grain boundary properties of nanostructured materials. In this paper, impedance spectroscopic analysis of grain and grain boundary properties of nanophase zinc oxide is discussed. The equivalent circuit parameters were determined by computer simulation. The grain boundary conductivity was found to be higher than that of the grains. Traps within or at grain boundaries of nanocrystalline ZnO capture free electrons from the adjoining grains resulting in the depletion of electrons in the grains and their accumulation at the grain boundary region, causing an enhanced conductivity of the grain boundary.