Structural And Magnetic Properties Of Mg Substituted Ni- Co Nanocrystalline Ferrite By Auto-Combustion Technique

Structural And Magnetic Properties Of Mg Substituted Ni- Co Nanocrystalline Ferrite By Auto-Combustion Technique

Structural And Magnetic Properties Of Mg Substituted Ni- Co Nanocrystalline Ferrite By Auto-Combustion Technique

P.G &Research Department of Physics, Abasaheb Garware College, Karve Road, Pune-411004, Maharashtra, INDIA

Abstract

Sol-gel auto combustion is a unique combination of the combustion and the chemical gelation processes. Structural and magnetic properties of Mg2+ substituted MgxNi0.8-x Co0.2Fe2O4 ferrites for x = 0.2, 0.4, 0.6 prepared by an auto-combustion method have been investigated. The nano size powders with compositions MgNiCoFe2O4 were synthesized by sol-gel combustion method. The puffy, porous brown powder as combusted was calcined at temperature of 4000C for 4 hour. Saturation magnetization decreased from 40 emu/g to 32 emu/g for sintered at400o C . These nanoferrites may have application in core materials and in electronic device technology. The prepared materials were confirmation of ferrite bonds studied by IR spectroscopy. The X-ray diffraction pattern of these compositions confirmed the formation of the nanocrystalline structure. Further, the XRD have been used to calculate the lattice parameter and grain size. The particle size of the synthesized compositions materials are varying from 23 nm to 21 nm. Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) respectively. The morphological investigations and nanometric sizes of the samples was studied by using scanning electron microscopy and transmission electron microscopic techniques. The average particle size was estimated about 20-

25 nm for calcined powders .UV visible spectroscopy of the material taken by UV-source Perkin Eimer Lembda-25 it found to be the prepared material in the range of semiconductor in

nature. Transmission electron microscopy (TEM) SADE found to be material is crystalline in nature.

Keywords: Sol-gel auto-combustion, Nanocrystalline, MgNiCoFe2O4, IR- Spectroscopy, X-ray diffraction, Scanning electron microscopy, Vibrating Sample microscopy, UV-Visible Spectroscopy, Transmission electron microscopy (TEM).

Corresponding Author: Dr. Rathod S. M.,

1. G. And Research Department of Physics, Abasaheb Garware College, Karve Road, Pune- 311003, [INDIA]

   1. Introduction

      The sol-gel auto-ignition method is used to speed up the synthesis of complex materials. It is the simple process, a significant saving in time and energy consumption over the traditional methods. This method is employed to obtain improved power characteristics, more homogeneity and have a narrow particle size, thereby influencing structural, electrical and magnetic properties of spinel ferrites [1]. Promising future applications of ferrite nanoparticles in medicine, making many devices like permanent magnets, memory storage devices etc. Ferrite nanoparticles have been the emerging

      focus of the recent scientific research.

      Spinel ferrites are an important class of compounds having large variety of electronic, magnetic and catalytic properties as they possess high resistivity and negligible eddy current losses. Ferrites are magnetic ceramics of great importance in the production of electronic components. Their

      applications range from simple function devices, such as small permanent magnets, to sophisticated devices for the electro-electronic industry. Some interesting applications of these materials are in computer peripherals, telecommunication equipment, permanent magnets, electronic, and magnetic media used in computers, recording devices and magnetic cards. The electrical and magnetic properties are the most important properties for ferrites depending on the processing conditions, sintering temperature, sintering time, chemical composition and the amount and type of the additives [2].The sol-gel chemical methods have given numerous advantages in terms of the properties and simplicity of the technique. The investigations on the nano-crystalline ferrite particles containing nickel and zinc using the sol- gel methods have been given much attention. However, the principle requirements of the ferrites have been less reported. The sol-gel route is relatively a new technique that uses organic compounds to produce ferrite cores, which at the moment imposes a high cost in its chosen starting materials [3-4].

      The magnetic properties of the nanosized ferrites are entirely different from those of their bulk counterparts, such as the super-paramagnetic behaviour and associated properties. Nanosized ferrites with uniform particle size and narrow size distribution are desirable for a variety of applications like targeted drug delivery, ferrofluids, medical imaging and other biomedical applications, magnetic data storage, etc., [5-8].ll manuscripts must be in English. These guidelines include complete descriptions of the fonts, spacing, and related information for producing your proceedings manuscripts. Ferrite nanocrystals are also of interest in various applications, such as inter-body drug delivery [9-11], bioseparation, and magnetic refrigeration systems [12-16], as they exhibit superparamagnetism

   2. Experimental

      1. Synthesis of nanoferrite:

         Mg substituted Ni-Co nanocrystalline ferrite MgxNi0.8-xCo0.2 Fe2O4 (where x = 0.2, 0.4, 0.6) were prepared by sol-gel auto-combustion technique. The precursor solution was prepared using AR grade metal nitrates; Mg(NO3)2, Co(NO3)2,

         Ni(NO ) , and Fe (NO ) . These nitrates were

         above solutions and continuously stirred for 30 minutes at 80o C. An aqueous solution of citric acid mixed with metal nitrate solution, and then ammonia solution was slowly added to adjust the pH at 7. The mixed solution was kept on to a hot plate with continuous stirring at 100o C. When finally all water molecules were removed from the mixture, the viscous gel began frothing.

         The materials used in this procedure for the preparation of MgNiCo ferrite are analytical grade of Magnesium nitrate, Nickel nitrate, Cobalt nitrate, Iron nitrate, and citric acid. The materials are weighed according to the required stoichiometric ratio. These nitrates and citrate were dissolved in suitable amount deionised water which was magnetically stirred at 750C until the mixture was homogenized. Liquid ammonia was added to the solution to adjust the pH value about 7. During this procedure the solution was continuously stirred using a magnetic stirrer. Then the mixed solution was heated at 1000C with constant stirring to transform it into a xerogel. When ignited at any point, the dried gel burnt in a self-propagating combustion manner until all the gel was burnt out completely to form a loose powder.

   3. Results and Discussions:

      1. Infra Red Characterization

         The disappearance of the characteristic bands of carboxyl group and (NO)3 ion in the IR spectrum curve after combustion revealed that the carboxyl group and the (NO)3 ion take part in the reaction during combustion. Therefore, the combustion can be considered as a thermally induced anionic redox reaction of the gel where in the citrate ion acts as a reductant and the nitrate ion acts as an oxidant. Because the nitrate ions provide an in situ oxidizing environment for the decomposition of the organic component, the rate of the oxidation reaction relatively increases.

         110

         100

         90

         intensity

         80

         70

         60

         50

         40

         30

         3 2 2 3 2

         initially dissolved separately in distilled water and stirred well for 20 minutes at 80o C, sbsequently the precursor solution was prepared by adding all

         0 500 1000 1500 2000 2500 3000 3500 4000 4500

         Wavelength

         FIGURE 1: IR graph of MgNiCoFe2O4

      2. X-Ray Diffraction

         The phase formation behavior of MgxNi0.8-xCo0.2Fe2O4 (where x = 0.2, 0.4, 0.6) was studied by XRD There was no metal oxide phase in the as burnt powder. The crystallite size was calculated from Full Width at Half Maximum (FWHM) for all the peaks using Scherrer formula:

         0.9

         was operated to 1 Tesla. Fig. 4 shows the magnetization curve of the MgNiCoFe2O4. as increasing the percentage of Mg the magnetization, coercivity and retentivity decrease.

         t cos

         (1)

         =full width at half maximum, =bragg angle for the actual peak.

         The lattice parameter was calculated by using the following formula:

         (2)

         FIGURE 2: XRD graph of MgNiCo ferrite where x The size of the particle is observed to be increased with increase in sintering temperature. While sintering generally decreases the lattice defects and strains, however it can also cause coalescence of crystallites that result in increasing the average size of the nanoparticles [17]

      3. Vibrating Sample Microscopy

         Saturation Magnetization has been determined from the force experienced by the ferrite specimen in the field gradient. It was measured using Vibrating Sample Magnetometer (VSM) (model 7307, Lake Shore). The principle of VSM is the measurement of electromotive force induced by magnetic sample when it is vibrated at constant frequency in the presence of a static and uniform magnetic field. A small part of sintered powder (0.0125 g) was weighted and made to avoid movements inside the sample holder. The VSM

         FIGURE 3 :VSM of MgNiCoFe2O4 (a)Mg0.2Ni0.6Co0.2Fe2O4

         (b) Mg0.6Ni0.2Co0.2Fe2O4

      4. Scanning Electron Microscopy

         The structural morphology for different proportions of MgxNi0.8-xCo0.2Fe2O4 (where x = 0.2, 0.4, 0.6) is studied by using scanning electron microscopy. The Figure 3 shows SEM graphs of the MgNiCo ferrite revealed that this material doesnt have a specific morphology and average grain sizes of the samples are determined from these micrographs..

         . This result agrees with the result for Zn2+, Cd2+, Ti4+ substituted ferrites [17, 18]. At low composition, formation of large exaggerated grains of non- uniform size is seen to occur. The driving force for grain growth is the surface tension of the grain boundary [19].

         FIGURE4:SEM,

         MgxNix0.6Co0.2Fe2O4.wherex=0.2,0.4,0.6

         FIGURE5:SEM,

         MgxNix0.6Co0.2Fe2O4.wherex=0.2,0.6

      5. UV-Spectroscpoy

      The figure (5) shows the UV-Visible spectroscopy absorption and reflection in the UV region. In the absorption molecules of – electron or non bonding (n-electron) can

      absorb the energy in the form of ultraviolet or visible light to excite this electron to higher or anti-bonding molecular orbit [20]. The band gap energy was calculated by following formula. The results of the samples have great influence on their optical property [21].

      E hc

      FIGURE6:UV-Specrta.

      F.Transmission Electron Microscopy

      The TEM micrograph of the synthesized nano particles along with selected electron diffraction (SAED) for MgxNi08-xCo0.2Fe2O4 ferrite shown in fig.2 a,b., fig.3 a,b. fig 4 a,b .The TEM micrographs shows the particles have a size distribution 20 to 25 nm (±1nm) .The agglomeration formed because they experience a permanent magnetic moment proportional to their volume[11].The SAED image of synthesized nano particles ,distinct ring that conforms good crystallinity are clearly visible.

      (a)

      It has been observed that particles are aggregated during annealing and metal ion incorporation. The

      crystalline lattice fringe is observed as uniformly extended over the primary building blocks, grain boundaries and pores in the samples annealed at

      	Grain Size	Constant
      	(nm)	()
      Mg0.2Ni0.6Co0.2fe2O4	23	8.211
      Mg0.4Ni0.4Co0.2fe2O4	22	7.960
      Mg0.6Ni0.2Co0.2fe2O4	21	7.210

      400o C for all compositions. Thus it can be

      FIGURE8:TEM MgxNix-0.6Co0.2Fe2O4 (a)0.2(b)0.6.

      TABLE 1. XRD calculation.

      concluded that the nanoparticles are organized in to an isooriented attached structure by sharing identical lattice planes.

      Composition Average

      Lattice

      TABLE 2. VSM calculation

      (b)

      Composition Magnetiz

      ation

      (emu/g)

      Coerci- vity (G)

      Reten tivity (emu/ g)

      FIGURE7:TEM MgxNix-0.6Co0.2Fe2O4.(a)0.2(b)0.6.

      Mg0.2Ni0.6Co0.2	39.585	728.71	19.41
      fe2O4			9
      Mg0.6Ni0.2Co0.2 fe2O4	32.823	643.93	15.04
      			1

      (a)

      (b)

   4. Conclusion

      In the present study MgxNi0.6-xCo0.2Fe2O4 (where x = 0.2, 0.4, 0.6) have been synthesized using low temperature Sol-Gel Auto-Combustion method. From above xrd result we found that there is no significant change in particle size but change in Lattice constant of the material decreases as percentage of magnesium increases . As the percentage of magnesium increases the magnetization, Coercivity and retentivity decreases. The morphology seen from the SEM images for MgxNi0.6-xCo0.2Fe2O4 where x = 0.2, 0.4, 0.6 revealed that the MgNiCo ferrite does not have any specific morphology. From UV spectroscopy we found that band gap energy of the material is 2.72eV, it means sample is in nature of semiconductor.TEM micrograph shows material is crystalline in nature.

   5. Acknowledgments

      We thanks to our Department of Chemistry,We also thank the Department of C-MET Pune, IIT Powai and the Department of Physics, University of Pune for their kind co-operation and providing

      their instruments for the purpose of characterization.

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