Annealing temperature and initial iron valence ratio effects on the structural characteristics of nanoscale nickel zinc ferrite

Abstract

Nickel zinc ferrite ͑NZFO͒ nanoparticles were synthesized via a reverse micelle method with a nonionic surfactant. Three different initial Fe 3+ / Fe 2+ ratios were employed along with three different firing temperatures ͑200, 500, 1000°C͒ to investigate the effects on the NZFO system. Extended x-ray absorption fine structure ͑EXAFS͒ results reveal zinc loss at high annealing temperatures; at 1000°C, the loss is nearly total for Fe 3+ / Fe 2+ ratios other than 10:90. Annealing at 500°C, however, appears necessary for fully incorporating the zinc and nickel into the spinel phase. The best nanoferrite was thus obtained using an initial Fe 3+ / Fe 2+ ratio of 10:90 and a moderate firing temperature of 500°C. This sample exhibits a room temperature saturation magnetization of 58 emu/g as measured via vibrating sample magnetometry, comparable with bulk values and greater than that of confirmed nano-NZFOs found in the literature. EXAFS also indicates that in all cases in which the elements adopted a spinel structure, the nickel occupies only octahedral sites and the zinc primarily tetrahedral sites.

Influence of Nd3+ substitution on structural, electrical and magnetic properties of nanocrystalline nickel ferrites

“…This method suffers from disadvantages like chemical inhomogeneity, coarser particle size and impurity insertion during the process [4]. In recent years several researchers have prepared nanosized ferrites by sol-gel method [2,5], emulsion method [6], co-precipitation method [2,7], citrate precursor method [8], tartrate precursor method [9], hydrothermal method [10], reverse micelle technique [11], microemulsions [12], high energy ball milling technique [13] and pulsed wire discharge method [14]. There are many reports in literature on the studies of Ni-Cr [15], Ni-Ge [16], Ni-Zn [17,18], Ni-Al [19], Ni-Cd [20], Ni-Li [21], Ni-Cu [22], Ni-Mg [23] and Ni-Mn [24] ferrites.…”

Correlating the effect of preparation methods on the structural and magnetic properties, and reducibility of CuFe2O4 catalysts

“…It has been reported that the cation distribution in the spinel structure could be inuenced by the particle size, the preparation method, the calcination temperature, and the cationdoping. [28][29][30][31][32] As the magnetic moments of cations located in the tetrahedral and octahedral sites couple in an antiparallel alignment, the net magnetization of the spinel ferrites is related to the difference between those of the octahedral and tetrahedral cations. 32 Accordingly, the change in the cation distribution can signicantly affect the magnetic properties of materials, e.g., saturation magnetization, coercivity and Curie temperature.…”

“…32 Accordingly, the change in the cation distribution can signicantly affect the magnetic properties of materials, e.g., saturation magnetization, coercivity and Curie temperature. 29,31 It is therefore important to gain the full structural information. The local structure and cation distribution of these CuFe 2 O 4 spinel nanoparticles were further determined by XAS analysis.…”