Influence of Cu dope on the structural behavior of MgFe2O4 at various temperatures

doi:10.1016/j.physb.2018.05.032

Physica B: Condensed Matter

Volume 544, 1 September 2018, Pages 73-78

https://doi.org/10.1016/j.physb.2018.05.032 Get rights and content

Highlights

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Mg1-xCuxFe2O4, (х= 0, 0.2, 0.4, 0.6, 0.8, 1) ferrites are studied at various temperatures.
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No phase transition of doped and undoped MgFe2O4 is observed up to 753K.
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The magnetization decreased with increasing temperature approaching zero at ∼753 K.
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Mg1-xCuxFe2O4 have higher magnetic moments than undoped ferrite samples.
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The lattice expansion and magnetization loss processes at high temperatures are hindered.

Abstract

The influence of Cu doping on the MgFe₂O₄ crystal and magnetic structure has been studied at various temperatures. A series of Mg_1-xCu_xFe₂O₄ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) spinels have been prepared by a chemical solid-state reaction method. The diffraction patterns confirmed that the formation of the single cubic spinel phase obtained for samples with a Cu content of up to 0.6. The second phase of a small amount of tetragonal CuFe₂O₄ phase was observed in the sample with x = 0.8. Cu doping increased and stabilized the magnetization of MgFe₂O₄ at a high temperature. The crystal phase of Cu doped MgFe₂O₄ was not changed up to 753 K.

Introduction

Amongst the spinel ferrite families, magnesium ferrite (MgFe₂O₄) is a soft magnetic n-type semiconducting material that finds applications in the fields of heterogeneous catalysis, adsorption, sensors and magnetic technologies [1,2]. Numerous studies have been carried out on the spinel ferrites which had the general formula (M_1-δFe_δ)[M_δFe_2-δ]O₄ due to their chemical and structural simplicity. The divalent metal element M (Mg, Zn, Cu, Fe, Co, Ni, or the mixture of them) can occupy either tetrahedral 8a (marked A) or octahedral 16b [marked B] sites of a spinel structure as depicted by the parentheses and brackets, respectively [[3], [4], [5]].

The crystal structure lies between a normal and an inverse spinel type that depends on the fraction of Fe³⁺-ions at the tetrahedral sites [6]. MgFe₂O₄ has a partially inverse spinel structure with the preference of Mg²⁺ cations mainly on octahedral sites [7,8], while copper ferrite (CuFe₂O₄) has an inverse spinel structure, in which all Cu²⁺ cations occupy octahedral sites [9,10]. Substitution of copper for MgFe₂O₄ resulted in the enhancement of permeability as well as magnetization values [11].

In our previous work [12], we performed a detailed investigation of the crystal structure of Cu doped MgFe₂O₄ at room temperature. In the present paper, structural properties of magnesium ferrite were explored at various temperatures. In order to test the phase stability and observe the structural evolution of the magnesium ferrite, some in-situ and ex-situ annealing experiments were performed under different temperatures, ranging from 298 to 753 K. Structural characteristics were studied by x-ray and neutron diffraction. Formation of ferrite was also confirmed by using Fourier-transform infrared spectroscopy (FT-IR). The main attention was paid to the evolution of the Mg_1-xCu_xFe₂O₄ under various annealing conditions.

Section snippets

Experimental

Mg_1-xCu_xFe₂O₄ type powder was prepared by a solid reaction method using MgO, CuO, Fe₂O₃ powder as a starting material [13]. Phase analysis of the samples were carried out using an x-ray powder diffractometer, Shimadzu XRD-7000 with CuK_α radiation and λ = 1.5406 Å. Neutron diffraction measurements were performed on the HRFD (High Resolution Fourier Diffractometer) instrument at the IBR-2 reactor, Joint Institute for Nuclear Research, Dubna, Russia [9]. FT-IR spectra were recorded for all samples

Phase analysis

Fig. 1 shows the XRD patterns of the Mg_1-xCu_xFe₂O₄ samples with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 which the peaks identified with Miller indices. The data showed intense sharp peaks and revealed well-crystalline single spinel structures. The result of phase analysis of patterns points out that the nominal composition structures with different concentrations have the cubic MgFe₂O₄ phase without any signature of impurity. A small amount of tetragonal CuFe₂O₄ phases were observed in the sample with

Conclusions

The temperature dependence of doping influence, crystal and magnetic structures above room temperature of Mg_1-xCu_xFe₂O₄, (х = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) ferrites were studied in detail. No phase transition of doped and undoped MgFe₂O₄ was observed up to 753 K, beside cubic to the tetragonal structural transition of CuFe₂O₄ appeared at 473 K. The magnetization decreased with increasing temperature approaching zero at ∼753 K for Cu doped MgFe₂O₄, which had higher magnetic moments than undoped

Acknowledgements

The authors are grateful to Prof. A.M.Balagurov and Dr. I.A.Bobrikov for their help in neutron diffraction experiments on the IBR-2 (JINR, Russia) neutron source. This work was partially supported by the Mongolian Foundation of Science and Technology (Grant No: 2017/24).

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View full text

Influence of Cu dope on the structural behavior of MgFe2O4 at various temperatures

Highlights

Abstract

Introduction

Section snippets

Experimental

Phase analysis

Conclusions

Acknowledgements

Jour. All. Comps

J. Magn. Magn Mater.

J. Magn. Magn Mater.

J. Magn. Magn Mater.

Jour. Mol. Str.

Results in Physics

Arch. Appl. Sci. Res.

Am. Mineral.

Indian J. Sci. Res.

Influence of Cu dope on the structural behavior of MgFe₂O₄ at various temperatures