Structure, Optical and Varistor Properties of One-Dimensional Co-Doped ZnO Synthesized by Reflux Method

Abstract

One-dimensional ZnO composites doped with different Co contents (0 mol.%, 1 mol.%, and 1.5 mol.%) were successfully prepared by the reflux method. Microstructural studies of the as-obtained powders were studied by x-ray powder diffraction, Fourier transform infrared spectra, and scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy. SEM observation showed that the morphology of ZnO particles is influenced by the concentration of Co doping, which formed rod-like and quasi-spherically shaped particles. All samples indicated a hexagonal wurtzite structure. When the Co content increased from 0 mol.% to 1.5 mol.%, the calculated crystallite size decreases from 56.62 nm to 54.38 nm. The change in bond length, lattice parameters, and micro-strain for Co-doped ZnO powders indicate that Co ions have entered the ZnO lattice. The study of the optical properties of ZnO powders proves that the doping of Co increases the absorptance and reduces the band gap of ZnO. The 1.0 mol.% Co-doped ZnO varistor sintered at 1200°C for 2 h has a breakdown voltage of 345.3 V/mm and nonlinear coefficient of 11.7.