Optical and electrical properties of undoped and (Mn, Co) co-doped ZnO nanoparticles synthesized by DC thermal

The undoped and (Mn, Co) co-doped ZnO nanopowders were synthesized through DC thermal plasma method. The pellets of this powder were annealed at 450, 550 and 650 degrees C for 1 h. Structural, chemical and optical properties of the samples were studied by XRD, SEM, EDX, UV-Vis and PL analysis. XRD spectra showed that all the samples were hexagonal wurtzite structure and as the annealing temperature increases the material becomes purer and more crystalline. It is seen that the optical band gap decreases when the ZnO is doped with manganese and cobalt. Photoluminescence intensity varies with doping because of the increment of oxygen vacancies. DC conductivity studies of the pellets were carried out at different temperatures (25-100 degrees C) and it was found that the activation energy for the electrical transport is high for (Mn, Co) co-doped ZnO than undoped ZnO. (C) 2011 Elsevier Ltd. All rights reserved.