Microwave assisted synthesis and characterization of Co doped Cu ferrite nanoparticles

Co doped Cu nanocrystalline ferrites with composition Cu1-xCoxFe2O4 (x = 0.0 <= x <= 0.5) were successfully synthesized through microwave assisted sol-gel method. Structural and electrical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), dielectric and impedance spectroscopy measurements. XRD analysis revealed the single phase cubic spinel structure of all samples with Fd3m space group. No secondary phase was detected confirming the substitution of Cu ions by Co ions in the Cu ferrite matrix. The average crystallite size calculated from XRD data was found to decrease from 28 to 10 nm with the increase in Co doping. Room temperature dielectric and impedance spectroscopy measurements showed that the dielectric constant, loss tangent and ac conductivity increases up to 3% Co doping and thereafter, these parameters decrease. The analysis of complex impedance data showed two semicircles, one corresponding to the grain and other corresponding to grain boundary volume which suggests that the conduction mechanism takes place predominantly through grain boundary volume as well as grains in the studied samples. The observed behavior of the samples has been explained on the basis of an electron-hole hopping mechanism in the light of Maxwell-Wagner two layer models and Koop's phenomenological theory, which is responsible for conduction and polarization. (C) 2012 Elsevier B.V. All rights reserved.