l-Ascorbic acid assisted synthesis and characterization of CoFe₂O₄ nanoparticles at different annealing temperatures

The effect of annealing temperature on structural, electrical and dielectric properties of cobalt ferrite nanoparticles has been discussed in this work. The cobalt ferrite nanoparticles were prepared by using sol–gel auto-combustion method taking AR grade nitrates of the constituent ions and l-ascorbic acid as a fuel. The as-prepared powder was annealed at temperatures 600, 800 and 1000 °C. The single phase nature of the prepared samples was confirmed through X-ray diffraction analysis. The particle size was estimated through Scherrer’s formula by considering the most intense peak i.e. (311). The particle size found to be in the nanometer range (32, 43 and 48 nm) and increases with increase in annealing temperature. XRD data was used to obtain other structural parameters and their variation with annealing temperature is discussed. Scanning electron microscopy and infra-red spectroscopy techniques were employed to characterize the prepared cobalt ferrite nanoparticles. IR spectra reveal the characteristic features of the spinel ferrite. The grain size obtained from SEM images was found to vary with annealing temperature. The electrical and dielectric behavior of the cobalt ferrite nanoparticles was studied by using two probe technique as a function of temperature and frequency respectively. The DC electrical resistivity varies inversely with temperature. The dielectric constant, dielectric loss and dielectric loss tangent all decreases exponentially with increasing frequency. The DC electrical resistivity decreases with increasing annealing temperature whereas dielectric parameters increase with increasing annealing temperature.