Effect of Annealing Time on Structural and Optical Properties of ZnGa2O4: Cr3+ (2.0mol %) Nanostructure Prepared by Sol Gel Method

Abstract

ZnGa2 O4 : Cr3+ (2.0mol %) nanopowders annealed at annealing times (AT) of = 1, 2, 3, and 4H (hour) were synthesized by the sol-gel method. X-ray diffraction (XRD) results confirmed that the prepared ZnGa2 O4 : Cr3+ samples were cubic structures. In this study we showed that the annealing time has no pronounced influence on the ZnGa2O4: Cr3+ crystallite size at annealing times in the range of 1H to 3H. A significant change in the crystallite size was observed for the sample annealed for a relatively long time (4H). Scanning electron microscopy (SEM) images show the morphology of the prepared nanopowders influenced by annealing time. UV-visible spectrophotometer measurements showed that the energy gap of the prepared nanoparticles could be tuned from 4.50 to 4.12 eV as the annealing time changed from 1H to 4H. Photoluminescence (PL) measurement showed that the annealing time increased, and the PL intensity also increased reaching the maximum value for the sample annealed at AT=3H. Energy dispersive X-ray spectroscopy (EDS) measurements confirmed the presence of Zn, Ga, O and Cr ions.