Ni-doped ZnO nanoparticles derived by the sol-gel method: structural, optical, and magnetic characteristics

A simple sol-gel route was used for preparation of Ni doped ZnO nanoparticles (Ni:ZnO) with 0, 3, 5, 7 and 9 wt % of Ni to Zn precursor salts. Structural, optical and room temperature magnetic properties were studied. The prevailing structural arrangement that observed in all the examined samples is the wurtzite structure of ZnO. Nevertheless. The orderly development of NiO rock-salt phase on at the surfaces of ZnO nanoparticles upon Ni doping is confirmed by Rietveld refinements. The ZnO wurtzite structure is dominant in all the samples as confirmed by both XRD and Raman results. The average crystallite size showed almost no change upon Ni doping. RTFM behavior is being exhibited for all Ni:ZnO nanoparticles that is demonstrating using of ZnO as the host structure allowed for the efficient formation of DMS. The Near-infrared solar reflectance (RNIR) and the visible solar reflectance (RVis) values reduced with increasing of the Ni content as a result of the rising in density of trap states upon Ni doping of the samples. Kubelka-Munk method was used to determine the energy band gap (Eg) and band Urbach energy (EU) tails from diffused reflectance (DRS) results. The obtained energy gap values were very close in all studied samples with an average value of energy gap is 3.164 eV. The EU values raise from 123 to 173 meV upon increasing of Ni content in the samples in agreement with lower values of RNIR and RVis and their effect on optical performance of the investigated samples in applications.