Structural and Electrical Studies of Aluminium-doped Nickel-Cobalt Ferrite Nanoparticles

Abstract: Aluminium-doped Nickel-Cobalt ferrite nanoparticles with general formula Ni0.5Co0.5AlxFe2-xO4 (x = 0 and x = 0.5) were synthesized by microwave-assisted sol-gel auto-combustion method. The X-ray diffraction analysis of the samples confirms single phase with cubic spinel structure belonging to space group Fd3m. The average crystallite size calculated using Debey-Scherrer formula was found to be in the range of 19-36 nm. XRD studies revealed that the lattice parameter (a), the particle size (D) and X-ray density (dx) decrease, whereas porosity increases with Al substitution. Energy Dispersive X-ray (EDX) was used to confirm the elemental composition of synthesized powders. TEM micrograph suggests that the particle size is in nanometric range, which confirms the nanocrystalline nature of the samples. The electrical resistivity and dielectric constant have been studied as functions of temperature. It was observed that the electrical resistivity decreases with increasing temperature, exhibiting the semiconducting nature of the sample. The dielectric constant increases with increase in temperature up to transition temperature and then decreases, which is explained on the basis of hopping mechanism. Keywords: Ni-Co ferrites, Sol-Gel, XRD, Resistivity, Dielectric constant.