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

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 °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 °C) and it was found that the activation energy for the electrical transport is high for (Mn, Co) co-doped ZnO than undoped ZnO.

Graphical abstractThe activation energy for the electrical transport is high for (Mn, Co) co-doped ZnO than undoped ZnO due to inadequate number of free hydroxyl groups on the surface.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► In this research, a novel DC thermal plasma reactor was used to produce undoped and (Mn, Co) co-doped ZnO nanoparticles. ► The activation energy of the electrical transport is high for (Mn, Co) co-doped ZnO than undoped ZnO. ► This property of synthesized ZnO pellets can be used for moisture sensing device applications.