Dielectric and Complex Impedance Spectroscopic studies of Microwave synthesized Cupric Oxide nanoparticles

Abstract

Abstract Hexamethylenetetramine (HMT) capped CuO nanoparticles were synthesized by microwave assisted technique. X-ray diffraction analysis confirms the formation of monoclinic single phase of the synthesized particles. The nature of ligand bonding and an estimate of the ligand molecules on the surface of CuO particles were obtained from Fourier Transform Infrared spectroscopy and Thermogravimetric analysis, respectively. Hysteresis measurements performed at 10 and 300 K show both the core-shell nature and the impact of the ligand. Dielectric measurements were performed with a temperature variation of 10 to 325 K and a frequency variation over 126 kHz to 949 kHz range. Broad relaxation peaks, reduction of dielectric constant with size and the presence of anomalies at slight variance to the magnetic transitions observed in bulk material, show signatures of the impact of ligand. Impedance spectroscopic (IS) analysis shows the room temperature impedance to be dominated by grain boundaries and reveals core-shell type of behaviour with conducting grains and insulating grain boundaries. A schematic is proposed with the grain consisting of the ligand capped CuO clusters separated by interfaces/grain boundaries.