1. Introduction
Ferromagnetism likewise spinel ferrites has general chemical formula M Fe2O4 (where M is a divalent metal ion of the transition metal elements, such as Mn, Fe, Co, Ni or Cu, Zn, Mg or Cd) [1]. These metals consider as an important and promising material which is widely used for various applications according to their outstanding electronic, optical, magnetic, and catalytic properties [2]. The spinel ferrite has three different types of spinels that are determined by the preference of cation occupancy for A and B-sites, namely normal spinel ferrite, inverse spinel ferrite and intermediate spinel ferrite. Typical examples for these categories are bulk zinc ferrite (Zn Fe2O4) for normal spinel ferrite, copper ferrite (CuFe2O4) for inverse spinel ferrite and magnesium ferrite (Mg Fe2O4) for intermediate spinel ferrite [3] [4] [5]. Ferrites based engineering materials have unique physical and chemical properties. Properties of ferrite are dependent upon several factors, such as composition of preparation, and doping of different cations, sintering temperature, sintered density, a grain size and distribution [6] [7]. Spinel ferrite plays an important role in a variety of technical fields, for example, ferrites have been used in Telecommunication, Digital memories for Computers, Channel filters, satellite communications memory, television industry, audio applications, satellite communications and radar [8] [9]. Doping ferrite as a new substituting method is an important class of materials. Spinel ferrites are examples for doping ferrites [10]. Several synthetic routes were employed for the development of aforementioned mixed ferrite system, namely sol-gel, co-precipitation, hydrothermal and the auto-emulsion methods [11].
The aims of this work are to study the effect of Cu (x = 0.0, 0.1, 0.2, 0.3, and 0.4) doped ZnMgFe2O4 nanocrystalline. The morphology and optical properties of the samples that prepared using sol-gel method were investigated. Different techniques were used such as X-ray diffractometer (XRD), elemental dispersive X-ray Spectroscopy (EDX), Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, UV-Vis, Spectroscopes.
2. Experimental and Method
Samples ZnMgFe2O4, CuFe2O2, MgFe2O4 and Zn0.5MS K0.5−x Fe2O4 where MS is Cu, K0.5−x is Mg and (X = 0.0, 0.1, 0.2, 0.3, 0.4) were prepared by using sol-gel the auto combustion method [12]. High purities of zinc nitrate [Zn(NO3)2∙6H2O (96%)], Copper nitrate [Cu(NO3)2∙3H2O (99%)], magnesium nitrate [Mg(No3)2∙6H2O (99%)], Ferric nitrate [Fe(NO3)2∙9H2O (98%)] and Sodium hydroxide (96%) were used as raw materials. The amount of metal nitrates in Cactus oil was Homogenous and separatism of metal ions were achieved by the use of sodium hydroxide. A required amount of sodium hydroxide added into the solution in order to modify pH value to about 7. The solution was constantly stirred for an hour at room temperature using magnetic stirrer. The obtained sol was heated at 80˚C in a magnetic stirrer to condensate into a gel, and then ignited in a self-propagating combustion manner to form a fluffy loose powder. Finally, the powders were grained by agate motor and the pellets were finally sintered at 750˚C for 4 h in a programmable furnace to remove any organic material present in samples.
Crystal structure of samples were investigated using X-ray diffraction (XRD) techniques—the shimadzu 60,000 X-ray diffract meter—with Cu-Kα radiation of a wavelength of λ = 1.5406 Å [13]. At room temperature, with nickel filter operating at 40 KV, 40 mA the data collected for the 2θ in 0.02-step size and five-second count in 0.02-step size and five-second count time 20 - 80 range. The MDI jade 0.5 programs used for the XRD data analysis. The crystallite size (D) calculated by Scherer equation [14].
“The SEM images were obtained on a Zeiss Ultra plus 55 field emission scanning electron microscopy (FE-SEM) (Carl Zeiss, Oberkochen, Germany) operated an accelerating voltage of 2.0 KV” investigated the morphology powder and analysis the elements energy dispersive X-ray Spectroscopy (EDX).The transmittance mode investigated for the sample by a (satellite FTIR 5000 of the wavelength rang of 400 to 4000 cm−1) [14] at room temperature. A Fourier transform infrared spectroscopy collected by KBr pellet method, the material mixed with KBr of ratio 1:100 for FTIR measurement between 400 and 2000 cm−1 [15] [16].
The UV-Visible absorption was investigated by UV Mini 1240 manufactured by Shimadzu company—Japan. Hydrochloric acid HCL was used as a reference for 100% absorbance [17].
3. Results and Discussion
3.1. Structural Analysis
The results of samples ferrites of Zn0.5CuxMg0.5−xFe2O4 with (X = 0.0, 0.1, 0.2, 0.3, and 0.4) are illustrated in Figure 1. The spectra showed the presence of peaks that correspond to (002), (110), (111), (310), (112), and (002) planes, where highly intense peak at (002) plane confirms cubic spinel structure of as- prepared material [11]. The lattice parameters constants (a) are found to decrease from (8.906 - 8.35) Åas the value of X increases. The particle size of the nanocrystalline varies from (30.56 - 40.58) nm. It can be noticed that the lattice constant decrease with increasing Cu concentration. This is maybe due to the fact that Cu2+ ions (0.73 Å) is larger than that of the Mg2+ ions (0.71Å) [7]. Addition of Cu2+ at the expense of Mg2+ in the ferrite is expected to decrease the lattice constant. The lattice constant (a), crystallite size (D), volume (v), space group, and relative density values of all the compositions are tabulated in Table 1.
The particle size of the nanocrystalline varies from (30.56 to 40.58) nm for different compositions. The observed variation in crystallite size of Cu2+ substituted Zn Mg ferrite supports the observed lattice constant variation results. From Table 1, it can be observe that the density increase with increasing Cu2+ content, exhibiting maximum 6.1 g/cm−3 for (X = 0.4). As magnesium has larger atomic weight than copper, the density of the sample without Cu doping (X = 0)
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Figure 1. XRD pattern for Cu-doped Zn0.5CuxMg0.5−xFe2O4 samples.
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Table 1. Crystallite size (D), Lattice constant (a), Volume (v) Space group and density of Zn0.5CuxMg0.5−xFe2O4 Nano-ferrites: where (X = 0.0, 0.1, 0.2, 0.3, 0.4).
is observed to be lower than that of Cu2+ doping (X = 0.4) sample. The values of weight and atomic are given in Table 2 [11]. The increase in density may be due to the ionic of constituent ions.
After analyzing the XRD data, the structural studies showed that all the samples prepared through the sol-gel method are single phase of a face-centered cubic (FCC) spinel and a symmetry structures with space group (SG: Fd-3m).
3.2. Morphological Properties
The morphological characteristics of the gained Zn0.5Mg0.5−xCuxFe2O4 X = 0.0, 0.1, 0.2, 0.3 and 0.4) nanoparticles are discovered with the high resolution Scanning electron microscopy and are shown in Figure 2. HR-SEM images of Zn0.5CuxMg0.5−xFe2O4 samples Figures 2(a)-(e) reveal that all the samples are displayed a close arrangement of homogeneous nanoparticles with prismatic shape. Figure 2(a) shows the presence of pure Zn0.5Mg0.5Fe2O4 nanoparticles, and Figures 2(b)-(e) shows the images of Cu- doped Zn Mg ferrite nanoparticles, which are homogeneous and agglomerated with diameter ranging from 1.9 to 2.4 nm. The SEM images of Figures 2(a)-(e) of Zn0.5CuxMg0.5−xFe2O4 reveal that the particle’s size and morphology of nanoparticles are an agglomerated due to the presence of magnetic interactions between the particles [18].
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Figure 2. (a)-(e) FE-SEM images of (a) Zn0.5Mg0.5Fe2O4; (b) Zn0.5Cu0.1Mg0.4Fe2O4; (c) Zn0.5 Cu0.2Mg0.3Fe2O4; (d) Zn0.5Cu0.3Mg0.2Fe2O4; (e) Zn0.Cu0.4Mg0.1Fe2O4 samples.
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Table 2. EDX analysis (weight % and atomic %) of Zn0.5Mg0.5−xCuxFe2O4 (X = 0.0 - 0.4).
3.3. EDX Spectroscopy Analysis
The EDX analysis is carried out to obtain an indication of the mount of Zn0.5CuxMg0.5−xFe2O4 series (X = 0.0, 0.1, 0.2, 0.3 and 0.4) are shown in Figures 3(a)-(e) and Table 2. The EDX spectroscopy is found to support the chemical composition of ferrites formations. The analysis fitting coefficients of iron, copper, Magnesium, Zinc, ferric, and oxygen of the individual nano-ferrite are generated by energy dispersive of SEM. From Figure 3(a) shows that the peak of Fe, Zn, Mg and O elements in pure Zn0.5Mg0.5Fe2O4 and Figures 3(b)-(e) shows the peaks of (Zn), (Cu), (Fe), (Mg) and (O) elements for Cu-doped Zn Mg Fe2O4 which is in agreement with(XRD) results. The presence of atoms C, Al, Si maybe attributed to carbon-coating for SEM measurement which was applied prior to EDX measurement.
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Figure 3. (a)-(e) EDX spectra of (a) Zn0.5Mg0.5Fe2O4; (b) Zn0.5Cu0.1Mg0.4Fe2O4; (c) Zn0.5Cu0.2Mg0.3Fe2O4; (d) Zn0.5Cu0.3Mg0.2Fe2O4; (e) Zn0.Cu0.4Mg0.1Fe2O4 samples.
3.4. Fourier Transform Infrared Spectroscopy
FT-IR spectra of investigating samples of Zn0.5CuxMg0.5−xFe2O4 ferrites with (X = 0.0, 0.1, 0.2, 0.3, 0.4) is shown in Figure 4 which are observed in the range of 4000 - 400 cm−1. All the samples show that many peaks which are responsible for different functional groups appear in the range 3600 - 1200 cm−1. Small peak at 3426 cm−1 indicated the presence O-H group, and C-H bending appears in 850 - 1200 cm−1. Two broad metal–oxygen bands are seen in the IR spectra of all spinel’s and ferrites in particular. The highest v1 is attributed to the intrinsic stretching vibrations of the metal at the tetrahedral site the lowest v2 band corresponds to the octahedral stretching vibrations [19]. The highest v1 band is generally observed in the range 650 - 600 cm−1 corresponds of intrinsic stretching vibrations of the metal at the tetrahedral site, whereas the lowers band (v2), usually observed in the range 450 - 380 cm−1, is assigned octahedral, metal stretching, the spectra showed prominent bands near 3426 cm−1 and 1600 cm−1 which were attributed to the stretching modes and H-O-H bending vibrations of the free or absorbed water.
3.5. Uv.vis Result
The optical absorption technique can be utilized for an examination of the optically induced transitions and can supply information about the energy gap in crystalline and Nano-crystalline materials. Figure 5 show UV-vis absorption spectra for the present study in particular the relation between optical absorption and wavelength of nanoparticle samples at room temperature. The absorption peaks of Zn0.5CuxMg0.5−xFe2O4 are found to be 255, 243, 234, 249, and 240 nm for (X = 0.0, 0.1, 0.2, 0.3, and 0.4) respectively. The optical band gap was obtained from the analysis of the spectral dependence of the absorption near the absorption edge Eg = 1242/λ. Regarding the optical transition arising from photons of energy (hv > Eg), the present optical data can be determined according to the following relationship of the near optical absorption, That estimated values of the band gap of Zn0.5CuxMg0.5−xFe2O4 (X = 0.0, 0.1, 0.2, 0.3, and 0.4)
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Figure 4. FT-IR for Cu-doped Zn Mg Fe2O4.
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Figure 5. (a) UV.vis Absorbance spectrum of Zn0.5CuxMg0.5−xFe2O4 samples.
nanoparticles are 4.87, 5.11, 5.30, 4.98 and 5.17 eV in the same order as in Figure 5 for X = 0.0 to X = 0.4. The results of the optical energy band gap of sample series indicated that they can be classified as insulator materials [20] [21].
4. Conclusion
Zn0.5CuxMg0.5−xFe2O4 series were synthesized by sol-gel route and the structural and morphological properties were studied by XRD and SEM. The samples were found to be cubic spinel-type structure with average crystallite size in the range of 30.56 to 40.58 nm. In the same way, the FE-SEM images showed morphology of the samples as prismatic shaped particles in agglomeration. EDX result confirmed the Elemental composition of the as-prepared spinel ferrite to the initial concentration of the synthetic composition used. The FTIR spectroscopy confirmed the formation of spinel ferrite. The energy band gap was calculated for samples were found to be in the insulator range.
Acknowledgements
I would like to thank the department of physics Al-Neelain University, particularly Laboratory of materials for supporting we carry out this paper. Thanks are also extended to the Physics Department, Pretoria University, South Africa for analyzing the Samples through SEM and EDX measurement.