Synthesis, structural, optical, electrical and Mössbauer spectroscopic studies of Co substituted Li0.5Fe2.5O4

Abstract

A series of cobalt substituted lithium ferrite Li0.5CoxFe2.5−xO4 with x=0, 0.2, 0.4 was prepared by a chemical technique called citrate precursor method. In this technique citric acid was used as a reducing agent. Structural, morphological, topographical, optical, electrical, and magnetic properties were studied by using X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, DC resistivity, Mössbauer Spectroscopy. XRD patterns showed characteristic (220), (311), (400), (422), (511), (440) peaks which confirmed the inverse spinel phase. SEM and TEM support the formation of cubic nanoparticles. FTIR studies reported the ferrite peaks between 400cm−1 and 800cm−1 confirming the inverse spinel structure. Five optical Raman modes (A1g+Eg+3F2g), characteristics of the cubic spinel structure with (P4332) space group are also observed. Electrical DC resistivity studied from room temperature to 300°C showed the semiconducting behavior of lithium ferrite. Porosity, transition temperature and activation energy are found to decrease with cobalt ion concentration. The room temperature Mössbauer spectra of all the samples showed normal Zeeman Splitting sextets supporting the formation of ferromagnetic phase. With increase in cobalt content, the value of hyperfine field at A site is found to vary from 53.15 to 54.96T whereas at B site it vary from 54.79 to 52.82T. The obtained results have been explained based on possible mechanisms, models and theories.