Comparative study of NiFe2-xAlxO4 ferrite nanoparticles synthesized by chemical co-precipitation and sol-gel combustion techniques

A series of aluminum substituted Ni-ferrite nanoparticles have been synthesized by chemical co-precipitation and sol-gel techniques. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), DC electrical resistivity and dielectric properties. Analysis of the X-ray diffraction pattern of all the samples confirmed the formation of spine! structure. The crystallite sizes remain within the range 25-41 +/- 3 nm. FTIR measurements show two fundamental absorption bands, assigned to the vibration of tetrahedral and octahedral sites. DC electrical resistivity increases from 6.60 x 10(7) to 6.9 x 10(10) Omega cm as the Al3+ concentration increases from 0.00 to 0.50. The dielectric constant and loss tangent decreases with increasing Al3+ concentration from 22 to 14, 0.354 to 0.27 respectively at 5 MHz for all the samples. Impedance measurements as a function of frequency (1 kHz-5 MHz) at room temperature further helped in analyzing the electrical properties of the prepared samples. (C) 2012 Elsevier Ltd. All rights reserved.