Cation distribution in nanosized Ni–Zn ferrites

Abstract

Nanoparticles of Ni1−xZnxFe2O4 (x=0.0, 0.25, 0.50, 0.75, and 1.0) in the size range of 6–12 nm have been synthesized by chemical precipitation followed by hydrothermal treatment. A strong correlation between the particle size and the zinc concentration has been identified. Mössbauer studies on these systems show that the cation distribution not only depends on the particle size but also on the preparation route. There are indications that in the present nanophase samples Fe occupies more tetrahedral sites as compared to the normal occupancy in the spinel ferrite structure. The occupancy returns to normal values after heat treatment at 1000 °C. Low-temperature Mössbauer studies indicate a significant amount of deviation of cation distribution from their bulk preferences.

Effect of Sintering Temperature on the Micro Strain and Magnetic Properties of Ni-Zn Nanoferrites

“…The lattice constant corresponding to each peak of the diffraction pattern was plotted against the Nelson-Riley error function [14] (F(θ) = ), and the accurate lattice constant, corresponding to zero error, was obtained by the least square fit. The lattice constant (Table 1) of the AP sample was found to be 8.397 Å, which is in well comparison with the reported values [10,15]. The crystallite size of the AP powder particles as determined by the Scherrer formula was 18 nm (Table 1) [16] using the intense (311) peak.…”

“…The site occupancy of a cation in the spinel lattice in general depends on several factors such as cation radius, crystal field effects, polarization effects, electrostatic energies, and temperature [28]. Moreover, finite particle size effects, methods of preparation, and sintering conditions play a vital role in deciding the site occupancy, wherein an inhomogeneous distribution is observed in several ferrispinels [3,10,24] with the cations occupying sites departing from their usual site preferences and thereby exhibiting several different structural, magnetic, and electrical properties at the nanoscale. Hence, in this study, examining the differences in the saturation magnetization, lattice strain, and lattice constant it is required to propose a suitable cation distribution, which could suffice the observed results.…”

“…The sintered Ni 0.58 Zn 0.42 Fe 2 O 4 at 1,473 K corresponds to the bulk material with a normal site preference for the cations, and the authors suggested that the nonequilibrium cation distribution and the canted spin arrangement resulting from the reverse micelle route is metastable, indicating that sintering restores an equilibrium configuration. Upadhyay et al [10] studied the cation distribution of the nanosized Ni-Zn ferrites prepared by the chemical coprecipitation method followed by the hydrothermal treatment using Mossbauer spectroscopy. The authors confirmed the restitution of the regular site preference of the cations upon sintering at ≥1,000°C.…”

Characterization of nanodimensional Ni-Zn ferrite prepared by mechanochemical and thermal methods

“…Figure 1 shows the RT Mössbauer spectra of samples obtained after different processing routes. The corresponding parameters, listed in Table 2, are typical of Fe 3+ ions in octahedral and tetrahedral spinel sites [1,6,7]. As shown in Figure 1A the spectra of all milled samples are doublets.…”

“…The Ni-Zn ferrites have been extensively studied for various properties as well as for structural issues [1][2][3][4]. Zn and Ni are known to have very strong preferences for the tetrahedral and octahedral sites, respectively, making Ni-ferrite a model inverse ferrite and Zn-ferrite a model normal ferrite.…”