Optical, magnetic and structural characterization of Zn1 − x Co x O nanoparticles synthesized by solvothermal method

Nanoparticles of Co-doped ZnO with 3·8, 7·2 and 11·5 wt% were synthesized by solvothermal method through oxalate precursor route. X-ray diffraction studies showed the formation of hexagonal ZnO structure for x = 0·038, however, secondary phase of Co3O4 arises on increasing the Co content up to 11·5%. Transmission electron microscopic studies showed that particles are in the nano-metric regime and the grain size decreases on increasing the Co concentration. Optical reflectance measurements showed an energy bandgap, which decreases on increasing Co concentration. Specific surface area of these nanoparticles was found to be very high and comes out to be 97·6, 112·1 and 603·8 m2g − 1, respectively. All the solid solutions showed paramagnetism with weak antiferromagnetic interactions. It is seen that the antiferromagnetic interaction increases on increasing Co concentration.