Nanoarchitectonics of zinc nickel ferrites by the hydrothermal method for improved structural and magnetic properties

Abstract

We report the structural and magnetic properties of zinc-nickel ferrites (ZNF), Zn1−xNixFe2O4, nanoparticles synthesized by the hydrothermal method with 0.0 ≤ x ≤ 1.0. The X-ray powder diffraction of Zn1−xNixFe2O4 shows the formation of a single spinel phase of ZnFe2O4 or NiFe2O4. The lattice parameter and unit cell volume decreased slightly as the x ratio increased, whereas the average crystallite size ranged from 9.55 to 22.7 nm. The nanoparticles’ morphology consists of small cubic and spherical particles with an average size increasing up to x = 0.6 and dropping at further increases of x. The assigned peaks obtained by the Fourier-transform infrared spectroscopy at 556–592 cm−1 verified the formation of metal (Zn, Ni, and Fe) oxides. The surface area, pore radius, and total pore volume were estimated using the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) theories and found to be dependent on the composition of the synthesized nanoferrites. Interestingly, we observed the largest surface area, SBET, of 264 ± 28 m2 g−1 at x = 0.6, which is three times higher than the other samples. The Zn1−xNixFe2O4 nanoferrites exhibited ferromagnetic behavior at room temperature with a saturation magnetization between 30.3 ± 0.01 and 126 ± 0.07 emu g−1. We found a possible link between maximum retentivity, corrective filed, and squareness with the surface area, especially at x = 0.6. The magnetic behavior at x = 0.4 could be attributed to the sample’s larger crystallite/particle sizes as compared to the other samples. Our results of the synthesized Zn1−xNixFe2O4 nanoparticles demonstrate the wide applicability of the ZNF nanostructures in magnetic storage as well as other applications that demand ferrite materials with a larger surface area.