Autocombustion High-Temperature Synthesis, Structural, and Magnetic Properties of CoCr_xFe_2–xO₄ (0 ≤ x ≤ 1.0)

Abstract

CoCr x Fe 2Àx O 4 (0 e x e 1.0) was synthesized by solÀgel auto combustion method using nitrates of respective elements and by keeping 1:3 ratio of metal nitrate to citrate. Representative sample was investigated by thermogravimeter/ differential thermal analyzer (TG/DTA); then, all samples were annealed at 500 °C for 4 h. The broad peaks in the X-ray diffraction patters (XRD) and evaluation of transmission electron microscopy (TEM) indicate a fine particle nature of the particles. Scanning electron microscopy (SEM) analysis and EDAX indicated that the samples were homogeneous and had the expected FeÀCoÀCr ratios. The lattice parameter, bulk density, and particle size are decreased, whereas the X-ray density, specific surface area, and porosity tend to increase with increasing Cr 3+ substitution. Cation distribution was estimated using XRD and by employing Bertaut method. Fourier transform infrared spectroscopy (FT-IR) is employed to determine the local symmetry in crystalline solids and to shed light on the ordering phenomenon. Saturation magnetization determined from vibrating sample magnetometer (VSM) decreases linearly with Cr 3+ concentration, suggesting that the superexchange interaction Fe(A)ÀOÀFe(B) link is stronger than that for the Fe(A)ÀOÀCr(B) link. Coercivity in the Cr-doped cobalt ferrites was larger than that in pure CoFe 2 O 4 compositions.

Influence of Zn2+ doping on the structural and surface morphological properties of nanocrystalline Ni-Cu spinel ferrite

“…Nanocrystalline magnetic particles with specific properties can be synthesized by different chemical techniques [1][2][3][4]. These properties are strongly dependent on their shape, size, crystallinity, and distribution of the cations among the tetrahedral (A) and octahedral (B) sites of the spinel structure.…”

Chromium Substituted Cobalt Ferrites by Glycine-Nitrates Process

“…This decrease in a with x can be explained based on the difference in ionic radii between the larger ionic radius Fe 3+ ion (0.67 Å) and the smaller ionic radius Cr 3+ ion (0.63 Å). [14,21] The average crystallite size of all the ferrite samples was ~ 230 Å. Figure 3.…”

“…The solution combustion process is characterized by high temperature, fast heating rates and very short reactions times. [21] The structural and morphological characteristics of the final oxides depend on the nature of the fuel and the oxidizer/fuel ratio. The ratio of the nitrates to fuel in the initial mixture was calculated using propellant chemistry concepts.…”

“…This ratio affects the velocity of the combustion, the temperature of the flame, and, implicitly, the features of the final oxides. [18,19,[22][23][24][25] In order to obtain nanosized chromium substituted cobalt ferrites, many research groups have used the solution combustion method with various fuels, like urea, [26] citric acid [21,27] etc. P. P. Hankare et al have developed a sol-gel autocombustion method to obtain nanocrystalline CoFe2-xCrxO4 powders (0  x  2) using citric acid as fuel.…”

Preparation and Characterization of Chromium Doped Ni-Cu-Zn Nano Ferrites

“…[17][18][19][20][21] Among these methods, the sol-gel method has gained scientific and technological importance during the last three decades. [22][23][24][25] The sol-gel auto-combustion synthesis method have many advantages as compared to the conventional methods such as low temperature processing and/or better homogeneity for the synthesis of multi-component materials. Considering the importance of Ni-Cu-Zn ferrite, we investigated the preparation of chromium doped Ni-Cu-Zn nano ferrite by sol-gel auto-combustion method using citric acid as fuel at low temperature with a view to study the influence of the substitution of Cr 3+ ion on the structural properties of the system.…”