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 spinel 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 × 107 to 6.9 × 1010 Ω 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.

AFM images of NiFe2O4 ferrite nanoparticles at room temperature synthesized by sol–gel technique.Figure optionsDownload as PowerPoint slideHighlights
► Particle size reduces to less than 30 nm.
► DC electrical resistivity increases with substitution of Cr3+.
► Dielectric constant decreases.