Synthesis and Structural Properties of MgFe2O4

Journal of Applied and Industrial Sciences, 2013, 1 (4): 20-23, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE)

Research Article

20

Synthesis and Structural Properties of MgFe2O4 Ferrite Nano-particles Mohamed I. M. Omer1,2*, A.A.Elbadawi2, O. A. Yassin2,3. 1

Department of Physics, Faculty of Education, Nile Valley University, Atbara 11121, Sudan. Department of Physics, Faculty of Science and Technology, Al-Neelain University, Khartoum 11121, Sudan 3 Department of Physics, Faculty of Science, TaibahUniversity, P. O. Box 30002, Universities road, AlMadinah Al-Monawarah, K. Saudi Arabia (Received August 18, 2013; Accepted October 20, 2013) 2

 Abstract— In the present work, MgFe2O4 magnesium nanoparticle ferrites has been synthesized by wet chemical method using high purity Ferric chloride and Magnesium chloride with oleic acid as the surfactant. The X-ray diffraction patterns of the magnesium ferrite combined with the Rietveld analysis method showed that the sample is cubic spinel ferrites particles with (SG: Fd-3m) and lattice constant ~ 0.84 nm. The estimated average ferrite particle sizes of Mg ferrites using the Debye-Scherer (DS) equation are found to be ~ 12.2nm. The scanning tunneling Microscopy showed that the particle size is of order of 50 nm larger than that obtained by the DS method. The reason is that the DS equation does not include the strain effect. A room temperature Mossbauer spectroscopy showed that the sample is superparamagnetic a typical behavior of the ferrites nanoparticles. Index Terms— Ferrite Superparamagnetic.

nanoparticles;

Particle

size;

I. INTRODUCTION

T

he small scale size of the well-known spinel ferrites has opened up the door for intensive research to utilize their properties for biomedical applications [1-3]. Numerous methods were reported in literature showing the possibilities of producing particle with size in the range of 2-100 nm. Among these methods are some chemical techniques like the coprecipitation, the hydrothermal and the sol-gel methods [4-6], which were reported to be fast and producing high quality nanoparticles. Cobalt ferrite (CoFe2O4) is one of the most important ferrites. It has a cubic structure of normal spineltype and is a soft magnetic. Superparamagnetic nanoparticles offer advantages of reducing risk of particle aggregation and act as attractive magnetic probes for biological imaging and therapeutic applications [7,8]. Preparation of CoFe2O4 (CFO) nanoparticles through chemical methods was reported by many authors to produce it with superparamagnetic property at room temperature [9]. CFO nanoparticle has proved to be good ferrofluidcore material for hyperthermia applications. There is long history of using fine powder of iron oxide ininvitro

*Corresponding author E-mail: [email protected]

diagnosis while recent studies have demonstrated that magnetite (Fe3O4) and maghemite (  -Fe2O3) are very promising candidates due to their bio-compatibility and relative ease to functionalize [10]. However, in order to achieve more safety for biomedical applications, these oxide nanoparticles must be coated by a biocompatible material. Some of these coating materials are polyvinyl alcohol, dextran and polyethylene glycol. The aim of this paper is to present the crystal structures at room temperature of the title compound and to report the observed phase transitions due to the Magnesium effect when it substitutes Cobalt. To the best of our knowledge, the synthesis MgFe2O4, reported in the present work, is the first preparation of this compound. II. MATERIALS AND METHODS Nanoparticle sample of MgFe2O4ferrites was prepared by the wet chemical route. Stoichiometric amounts from pure raw materials of FeCl3.6H2O, MgCl2.6H2O and NaOH were used to prepare the required solutions with required molarities. The solutions of FeCl3.6H2O 0.4M (25ml)and MgCl2.6H2O 0.2M (25ml) were first mixed and then slowly added to a 3MNaOH(25ml) solution under stirring of 3000 rpm for 30 minutes to obtain a mixture of pH 11–13. A specified amount of oleic acid was added to the solution as surfactant and coating material [11]. The colloidal solution was then kept in a water bath at 95oCfor 2 h. To assure removal of NaCl from the powder, the produced precipitate was washed 10 times with hot deionized water until the filtrate had a pH7. The phase purity of the sample was verified using XRD with a Shimadzu 6000 X-ray diffractometer equipped with Cu-k radiation of a wavelength of =1.5406 Å. The data were collected in a 2  range from 20o to 70o at a step size of 0.02. The phase purity and the lattice parameters were determined using the FullProf suite [12]. The particle size was determined by an Easyline scanning tunnelling microscope (STM). Furthermore Mossbauer spectra were collected at 300 at a constant acceleration. The spectrometer was calibrated with αFe foil at room temperature.

Journal of Applied and Industrial Sciences, 2013, 1 (4): 20-23, ISSN: 2328-4595 (PRINT), ISSN: 2328-4609 (ONLINE) 21 III. RESULTS AND DISCUSSION Structural and magnetic characterization of MgFe2O4 The structural and the magnetic properties of the ferrites spinels are sensitive to the details of the preparation methods [13]. Therefore, it is very important to characterize the material. The x-ray diffraction pattern recorded for MgFe2O4 (MFO) is shown in figure 1. It resembles that MFO has a small grain size as the diffraction peaks are broad having low intensity. The formation of single phase MgFe2O4 is confirmed after analyzing the x-ray diffraction patternby the FullProf suites as appears in figure 1. The crystal structure is found to cubic with space group (SG) Fd-3m and a lattice parameter

140

(311)

Experimental data Fitting Difference Bragg Reflection

120 100

Intinsity (a.u)

8.4210 (26) Å, as expected for the ferrites structures. The XRD patterns of the calcined MgFe2O4 are shown in Fig1. All of the main peaks are indexed as the spinel MgFe2O4 in the standard data (Shimadzu 6000 X-ray diffractometer equipped with Cu-k radiation of a wavelength of =1.5406 Å. The data were collected in a 2  range from 10o to 80o at a step size of 0.02. ). The average crystallite sizes of MgFe2O4 samples were calculated from X-ray lines broadening of the reflections of (220), (311), (400), (442), (511), and (440) using Scherrer’s equation (i.e., D = 0.89k/(β cosθ), where k is the wavelength of the X-ray radiation, K is a constant taken as 0.89, h the diffraction angle, and b is the full width at half-maximum [14].

80

(440)

(220)

60

(511) (442)

(400)

40 20 0 -20 -40 -60 20

30

40

50

2

60

70



Figure 1: The x-ray diffraction pattern of MgFe2O4. The figure shows the broaden pattern which indicates the nano phase. It also represents the experimental data, the fitting, the difference line and the Bragg reflections. All the solid line corresponds to the results of the fitting by employing the Rietveld method.


Figure 2: The STM image of the MgFe2O4 The figure illustrates the particle size from its morphology, which verifies the nano structure. The particle size is found to be of the order of 50 nm as detected by STM, figure 2. Since MFO can exist in either cubic (SG: Fd3m) [14] or tetragonal (SG: I41/amd) structures [15]. The room Mössbauer spectra (MS) for MFO is shown in Figure 3. It shows a dominating double and sextet broad absorption peaks. The first one resembles the occurrence of super paramagnetic relaxation due to the small scale size of the MFO particles and the second one reflects a normal Zeeman

splitting of 57Fe nucleus. The doublet peak was fitted assuming two doublets where the first was assigned to the surface and the second to the internal domain of the particles. The results of the fitting parameters are given in figure 3 and table 1. These results show that the quadrupole splitting for the internal domain is considerably smaller than that of the surface where the first one is 0.808 mms-1 and, the later one is 1.813 mms-1. This variation may be related to spin disorder at the surface and wide range distribution of the atomic spacing [16].

6

4.6x10

MgFe2O4 R T

6

Relative Intensity

4.6x10

6

4.5x10

6

4.5x10

6

4.5x10

6

4.5x10

6

4.5x10

6

4.4x10

6

4.4x10

6

4.4x10

-15

-10

-5

0

5 -1

Velocity (mms )

Figure 3: Room temperature Mössbauer spectra of MgFe2O4.

10

15


The figure shows the sextet phase and doublet one also can be observed. That confirms the magnetic behaviour of the sample, which can be too interesting to discuss. The whole MS data are then refitted by inclusion of sextets. It was found that a good fitting can be obtained only including four sextets, one corresponds to the tetrahedral site and three correspond to the octahedral sites. In the second process of

23 fitting, the parameters of the fitted doublets obtained previously were kept fixed and allowed the parameters of the sextets to vary. In terms of the percentage of the intensities of the sextets, the cation distribution between the A- and the Bsites can be estimated to be [Mg0.182Fe0.818]A[Mg0.541Mg0.409]2BO4 resembling that MgFe2O4 is a mixed ferrite.

Table 1 The results of the fitting parameters of the Mossbauer data measured at room temperature. I.S. (mmsec-1) Q. S. HF (Tesla) FWHM Doublet 1 0.443 0.808 0.769 Doublet 2 0.457 1.813 0.789 Sextet 1 0.482 0.000 48.345 0.895 Sextet 2 0.548 0.000 51.021 0.783 Sextet 3 0.482 0.000 44.200 0.767 Sextet 4 0.470 0.000 26.662 1.076 IV. CONCLUSIONS From the results we concluded that: Fine powder sample of MgFe2O4 (MFO) was prepared by the co-precipitation method and well characterized by X-ray diffraction, Scanning Tunneling Microscope (STM) and Mössbauer spectroscopy. The sample was found to be superparamagnetic cubic spinel ferrite. Further, as a strategy for enhancing the performance of the particle size, the scanning tunneling microscope (STM), and the X-ray diffraction (XRD) results confirm the nanoparticle structure. ACKNOWLEGEMENTS Mohamed I. M. Omer would like to thank the office of the external activities, Abds Salam International centre for Theoretical Physics (ICTP) Trieste, Italy, for the financial support provided to him as a part of the project No. PRJ-28 provided to the department of Physics, Al-Neelain University, Sudan. REFERENECES [1]Kumara C. S .SR and Mohammad F. Magnetic Nanomaterials for Hyperthermia-based Therapy and Controlled Drug Delivery. Adv. Drug Delivery Reviews. (2011) 63, 789. [2] GIRI J, PRADHAN P, SOMANI V, CHELAWAT H, CHHATRE S, BANERJEE R, BAHADUR. SYNTHESIS AND CHARACTERIZATIONS OF WATER-BASED FERROFLUIDS OF SUBSTITUTED FERRITES [FE1−XBXFE2O4, B=MN, CO (X=0–1)] FOR BIOMEDICAL APPLICATIONS. J. MAG. MAG. MAT. (2008) 320,724. [3]Sharifi I, Shokrollahi H, Amiri S. Studies of preparation and characterization of the magnetite-sodium alginate/PEO nanofibers and its hyperthermia effect in vitro J. Mag. Mag. Mat. (2012) 324,903. [4] ChenY, Ruan M, Jiang Y. F, Cheng S.G, Li W. The synthesis and thermal effect of CoFe2O4 nanoparticles. J. Alloys and Comp. (2010) 493, L36.

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