Optical, Structural, and Magnetic Properties of ZnO:Co Nanoparticles Prepared by a Thermal Treatment of Ball Milled Precursors

In this study, ZnO nanoparticles with different cobalt concentration were prepared by a simple and rapid method. This method is based on a short time solid state milling and calcinations of zinc acetate, cobalt acetate, and citric acid powders. The samples were characterized using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FTIR), photoluminescence, and UV-vis. spectroscopy. It was shown that a very low substitution of Co (less than 1% of molecular weight) has little effect on the lattice parameters of ZnO and significantly decreases the band gap (Eg) value of the synthesized ZnO:Co nanoparticles. Calculation based on the XRD data shows that the average crystallite sizes of ZnO particles are nearly 18 nm. Photoluminescence spectroscopy shows that many defects such as interstitial zinc, zinc vacancy, and exciton recombination are responsible for the observed optical properties. Magnetization measurements which were performed by using a superconducting quantum interference device (SQUID) magnetometer determine the paramagnetic behavior for all samples due to the absence of oxygen vacancy.