Effect of Ni-doping on structural, dielectric, and magnetic properties of CdO nanoparticles

In the present studies, we are reporting synthesis, structural, microstructural, optical dielectric, and magnetic properties of pristine and Ni-doped CdO (Cd${}_{1-x}$Ni${}_x$O, 0% ≤ x ≤ 10%) nanoparticles. Co-precipitation method was used to synthesize these nanoparticles. X-ray diffraction patterns show the cubic phase of polycrystalline Cd${}_{1-x}$Ni${}_x$O nanoparticles along with the formation of secondary NiO phase at higher Ni-content. The XPS spectra indicate the presence of oxygen vacancies along with mixed oxidation states of nickel (Ni${}^{2+}$ and Ni${}^{3+}$) and cadmium (Cd${}^{2+}$, Cd${}^{4+}$). FESEM micrographs show non uniform distribution of grains in these nanoparticles. The observed Raman peaks show that Ni${}^{2+}$ ions are successfully substituted at the Cd${}^{2+}$ lattice sites in the host lattice of CdO. The decrease in ac-conductivity of CdO with Ni-doping indicates the segregation of defects (Cd interstitials and oxygen vacancies) at grain boundaries. The conduction phenomena are explained by correlated barrier hopping mechanism in these nanoparticles. The optical band-gap broadening of CdO with Ni-doping show the influence of carrier densities. Ferromagnetic ordering in these nanoparticles is explained using bound magnetic polarons' (BMPs) model.