The effect of growing time and Mn concentration on the defect structure of ZnO nanocrystals: X-ray diffraction, infrared and EPR spectroscopy

Abstract

ZnO nanopowder was synthesized via a hydrothermal route and characterized with several methods such as XRD, TG/DTA, FT-IR, FE-SEM, TEM and Electron Paramagnetic Resonance spectroscopy (EPR) in order to investigate the effect of growing time and Mn doping on the defects which occurred. The pure ZnO nanopowder was obtained in a hexagonal phase with (101) as the preferred orientation except for the one prepared for 36 h which is (002). The growing time does effect the orientation of the crystallite whereas the Mn-doping does not. The concentration of Mn²⁺ significantly increases the spin–spin interaction in the ZnO : Mn nanopowder. It was observed that there was a competition between intrinsic (Zn and O vacancies) and extrinsic (Mn²⁺ ion) structural defects but still the former defects are dominant in ZnO : Mn. The effect of growing time and concentration of Mn²⁺ on the activation energy of ZnO and the ZnO : Mn nanopowder are calculated by Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods.