Investigation of structural, optical and electronic properties of (Co, Ni) codoped CeO₂ nanoparticles

Cerium oxide co-doped with cobalt and nickel, is synthesized using sol-gel method. The phase purity and crystal structure are confirmed using x-ray powder diffraction (XRD). Rietveld analysis of XRD data confirms cubic fluorite structure of undoped and (Co, Ni) co-doped CeO₂. Lattice strain increases with codoping which results in reduction of crystallite size, lattice disorder and defects. UV-vis absorption analysis shows that co-doping leads to huge reduction in bandgap from 3.05 eV to 2.31 eV; this is due to the presence of defects and disorder as confirmed by Urbach energy calculation. Raman and Photoluminescence (PL) analysis shows that oxygen vacancies related defects are increasing with codoping. These defects leads to lattice disorder and shifts the bandgap from UV region to visible region by modifying its electronic levels.