Structural and Optical Properties of ZnO Nano-Powder Synthesized by Combustion and Sol-gel Method

Abstract

Nowadays, ZnO is considered as the most important chemical compounds due their distinctive properties owing to its wide band gab and large exciton binding energy. It is well known that the structural and the optical properties of ZnO differ by different methods of preparation. Therefore, in this work, ZnO power was prepared by two methods, namely sol-gel and combustion method with the aim of comparison. The obtained samples from both methods were investigated by many techniques for considerable comparison. The obtained results from ZnO synthesized by the sol- gel method showed that the crystallite size of ZnO was increases by increasing of the annealing temperature. Also little change in the lattice parameter was observed when the annealing temperature increased. It is observed also that similar structure of ZnO prepared by sol-gel and combustion can be obtained at particular conditions. TEM studies showed that the ZnO nanocrystals are irregularly spherical with average diameter of 32 nm, which is similar to the calculated crystallite size from the XRD data. The calculated energy band gab of ZnO prepared by combustion method is found to be 3.2 eV while for samples prepared by sol-gel method is found to be increased with increasing the annealing temperature. There was a clear difference between the two PL spectra obtained from ZnO synthesized by sol-gel and combustion method which is assigned to be due to complicated defect chemistry relevant to the experimental process.