Structural and magnetic characterization of Co2+ substituted Ni-Zn ferrite nanoparticles synthesized by refluxing co-precipitation and their potential application as gas sensors

Abstract

This work investigates the effect of Co2+ content on the structural, magnetic, and gas sensing properties of Ni0.3Zn0.7-xCoxFe2O4 (x=0.00, 0.05, 0.15, 0.25, 0.35) nanoferrites synthesized by refluxing co-precipitates of metal chlorides. X-ray diffraction and electron microscopy were used to study the structure and morphological aspects of the materials. X-ray diffraction (XRD) patterns revealed single-phase nanomaterial with shrinking lattice constants from 8.41 to 8.38 Å with increasing Co2+ content. The crystallite sizes varied slightly between 9.95 and 10.06 nm. The vibrating sample magnetometer (VSM) was used to extract information of the magnetization of the materials at room temperature. Saturation magnetization increased from 39.5 to 48.5 emu/g from x = 0 to 0.25 and dropped at x = 0.35 to 46.2 emu/g. Furthermore, the coercivity, effective anisotropy constant and remnant magnetization increased from 170 to 400 Oe, 696 to 1925 erg/Oe, and 1.15 to 2.72 emu/g respectively. A distinct correlation between the inverse initial magnetic susceptibility and unit cell volume of the materials was found. Room temperature 57Fe Mössbauer spectra revealed a magnetic transition from paramagnetic to ordered magnetic phase with increased Co2+ content. Except for sample with x = 0 and 0.15, where suspected co-existence of Fe3+ and Fe2+ was observed Fe3+ ions were observed. Zn2+ ions were found to largely occupy the B sites. Specific surface area and the average pore size distribution increased from 61 – 85 m2 g−1 and 22 – 25 nm respectively, with the addition of Co2+ content. The composition x= 0 showed exceptional response to propanol suggesting good suitability for sensor fabrication. All samples revealed the selectivity preferences in the order of propanol > ethanol > methanol.