Abstract
The present study envisages the preparation of chromium substituted Nickel ferrite NiCrxFe2−xO4 (x = 0~1.0) powders by a sol-gel auto-combustion method. X-ray diffraction analysis (XRD) showed that the specimens with x > 0.2 exhibited a single-phase spinel structure, and that more content of Cr within a specimen is favorable for the synthesis of pure Ni-Cr ferrites. The lattice parameter decreased with an increase in the Cr concentration. The sample without calcining exhibited a good crystallinity. Scanning Electron Microscopy (SEM) showed the formation of ferrite powders nano-particles, and that the substitution of Cr weakened the agglomeration between the particles. Mössbauer spectra of NiCrxFe2−xO4 showed two normal Zeeman-split sextets that displayed a ferrimagnetic behavior. Furthermore, the spectra indicated that iron was in the Fe3+ state, and the magnetic hyperfine field at the tetrahedral tended to decrease with an increase in the Cr substitution. The saturation magnetization decreased by the Cr3+ ions, and reached a minimum value (Ms = 4.46 emu/g). With an increase in the annealing temperature, the coercivity increased initially, which later decreased.
Highlights
Nickel ferrite (NiFe2 O4 ) is a typical soft magnetic ferrite, making it one of the most important spinel ferrites [1]
X-ray diffraction analysis (XRD) results show that the specimens with x > 0.2 exhibited a single-phase spinel structure, while an impurity peak of Fe2 O3 was detected in the samples with x = 0 to 0.2
XRD analysis of the NiCrx Fe2−x O4 ferrite reveals that the specimens with x > 0.2 exhibit a single-phase spinel structure, while the impurity peak of Fe2 O3 was detected in the samples with x = 0 or 0.2
Summary
Nickel ferrite (NiFe2 O4 ) is a typical soft magnetic ferrite, making it one of the most important spinel ferrites [1]. The magnetic and electric properties of the spinel ferrites depend on the distribution of the cations among tetrahedral and octahedral sites. Patange et al investigated the cation distribution and magnetic properties of chromium-substituted nickel ferrite, and found that Cr3+ and Ni2+ ions both have strong preference to occupy octahedral (B) site, and the magnetic saturation and Curie temperature all decrease by Cr3+. Prasad et al prepared nanoparticles NiCrx Fe2−x O4 by sol-gel, and concluded that the magnetization and coercivity decreased with an increase in the chromium ion concentration, due to the depletion of Fe3+ ions at the octahedral (B) sites [5]. From previous studies [4,5,6], it is evident that increasing the substitution of Cr is favorable for the synthesis of pure Ni-Cr ferrites, and weakens the agglomeration between the particles
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