Structures and properties of Mg0.95Mn0.01TM0.04O (TM = Co, Ni, and Cu) nanoparticles synthesized by sol–gel auto combustion technique

The room temperature structural, optical and dielectric properties of Mg0.95Mn0.05O and Mg0.95Mn0.01TM0.04O (TM = Co, Ni, and Cu) nanoparticles are reported. All transition metal nanocrystalline samples were successfully prepared by sol–gel auto combustion method. X-ray powder diffraction patterns at room temperature confirmed the formation of single-phase cubic structure with an Fmm space group for all prepared samples. Slight variation in the lattice parameter of TM doped Mg0.95Mn0.05O has been observed. Using Rietveld refinement of XRD data, the space group and lattice parameters are determined. Scanning electron microscopy (SEM) measurements were performed to understand the morphology and grain size of the Mg0.95Mn0.01TM0.04O (TM = Co, Ni, and Cu) nanocrystals. The estimated band gaps as calculated by using UV-Vis spectroscopy are found to be 3.59, 3.61, 5.63 and 3.55 eV for Mg0.95Mn0.05O and Mg0.95Mn0.01TM0.04O (TM = Co, Ni, and Cu) nanocrystals, respectively. Both dielectric constant and dielectric loss is found to decrease due to TM (transition metal) doping. The ac conductivity is found to increase with increase in frequency. Electric modulus spectra reflect the contributions from grain effects: the large resolved semicircle arc caused by the grain effect. The results obtained in this study were discussed comparatively with those cited in the literature.