Rietveld refinement and cation distribution of Zn-Al substituted NiFe2O4 ferrite nanoparticles

Abstract

A series of Zn-Al co-substituted nickel ferrites having general formula Ni1-xZnxFe2-yAlyO4 with x = y = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 were successfully synthesized by wet chemical sol–gel auto combustion method. The X-ray diffraction pattern with Rietveld refinement has confirmed the formation of monophase cubic spinel structured samples with space group Fd-3 m. It is found that the lattice constant (a) decreases from 8.3399 Å to 8.2801 Å with an increase in Zn-Al content. The crystallite sizes are decreased from 25 nm to 18 nm with Zn-Al content. The X-ray density is decreased from 5.3679 to 4.9642 g/cm3 and porosity is decreased from 32.23 to 30.68 % with Zn-Al substitution. The cation distribution attributed that the dopant Zn2+ preferentially occupies tetrahedral A-site and dopant Al3+ preferentially occupies octahedral B-site for all the composition of Zn-Al. The average grain size (G) is observed to be increased from 36 nm to 43 nm. The saturation magnetization (Ms) is decreased from 48.51 to 1.05 emu/g with Zn-Al composition. The coercivity (Hc) of the sample is decreased from 104 to 26.31 Oe and the remenance ratio is decreased from 0.23 to 0.03 Zn-Al content. The variations in dielectric properties are explained on the basis of Maxwell and Wagner’s type of interfacial polarization effects. The magnetic and dielectric properties of nickel ferrite nanoparticles are strongly influenced by the Zn-Al co-substitution, which is valuable in technological applications.