Structural, morphological and electrical properties of Cr2O3 nanoparticles

Chromium oxide (Cr2O3) nanoparticles have been prepared by chemical precipitation followed by calcination at high temperatures. The influence of calcination temperature on the particle size, microstructure, surface area and morphology was examined by X-ray diffraction, Fourier transform infrared, N2 adsorption–desorption isotherms, transmission electron microscopy and thermal analysis techniques. The results indicate the formation of a nanosized single Cr2O3 phase. The particles possess high specific surface area and mesoporous structure, and their sizes increase with increasing the calcinations temperature. DC conductivity was measured in the temperatures range of 170–475 K. For the high temperature region, the conduction was found to be due to small polaron hopping of holes. While for the low temperatures region, the conduction was attributed to variable range hopping mechanism of holes. The temperature dependence of the AC conductivity and dielectric constant was investigated in the same temperature range at four test frequencies. In addition, the impedance spectra of these nanoparticles were investigated only at temperatures above 350 K.

► Cr2O3 nanoparticles have been prepared by chemical precipitation method.
► The XRD particle sizes are in a good agreement with those obtained by TEM.
► The particles size and porosity depend on the calcination temperature.
► Electrical measurements were done in a wide temperature range as functions of particle size.
► The conduction was interpreted by small polaron hopping and variable range hopping mechanisms.