Preparation and characterization of Mn-Zn Nanoferrites by Oxalate Precipitation Method

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International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)

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ISSN (Print): 2319-3182, Volume -7, Issue-2-3, 2018 1

Preparation and characterization of Mn-Zn Nanoferrites by Oxalate Precipitation Method

1Tanuj Sharma, ²M. Singh, ³B.Chauhan, ⁴A.Thakur

1FCET Ferozepur, Punjab India,

2,3HPU Shimla

4Shoolni University Solan

Email: ¹[email protected], ²[email protected], ⁴[email protected] Abstract— In the present study preparation and

characterization of Mn-Zn nano ferrites with formula MnxZn1-xFe2O4, where x = 0.3, 0.5 and 0.7 by oxalate precipitation method has been reported. Micro structural properties studied with the help of X-ray diffraction have single phase spinel structure. The properties like initial permeability, permeability loss, dielectric constant, dielectric loss are studied as function of frequency. The electric loss factor has been observed to be high at low frequencies which decrease to low values at high frequencies The permeability loss factor has been observed to be high at low frequencies which decreased sharply to low values at higher frequencies and then again increased. These variations have been understood in terms of the variation of real and imaginary values of the initial permeability for these nano ferrites. The dispersion in magnetic and electrical properties has been discussed by using various models and theories.

Index Terms— initial permeability, permeability loss, dielectric constant, dielectric loss, d.c. resistivity

I. INTRODUCTION

Soft ferrites such as Mn-Zn and Ni-Zn have a wide range of applications in electronic components such as inductors, wide band transformers, antenna cores, HF transformers [1-5]. Spinel Ni-Zn ferrites are particularly suitable for read-write heads used in high speed digital tapes or discs [6]. The electrical and magnetic properties of soft ferrites have been studied by many workers [7-11].

The usefulness of the ferrite is strongly influenced by the physical and chemical properties of the materials and depends upon many factors including the processing technique used to synthesize them. In order to get good quality ferrite with reproducible stoichiometric composition and desired microstructure, a recently reported oxalate precipitation method has been used to synthesize ferrite. In the present communication, we have studied the properties like initial permeability, permeability loss, dielectric constant, dielectric loss and d.c. resistivity of MnxZn1-xFe2O4 ferrites with x = 0.3, 0.4 and 0.5.

II. EXPERIMENTAL DETAILS

The composition of spinel ferrite system MnXZn1-xFe2O4

(x=0.3, 0.4, 0.5) were prepared by oxalate precipitation method. The sulphates MnSO4, ZnSO4, FeSO4 were taken in stoichometric proportion and dissolve in the distilled water, the pH of the solution was properly maintained.

The solution of ammonium oxalate was added into the mixture excessively in order to complete the process of precipitation. The precipitate was the solid solutions of Mn, Zn & Fe oxalates. It was then filtered, washed with water in order to remove sulphate ions. The removal of sulphate ions was confirmed by barium chloride test. The precipitate was finally dried. The residue is dried and was calcinated in a box type furnance for 3 hours, at 700^oC to obtain a ferrite power the characterization of compositions were done by using standard tools like x-ray power diffraction. Now this powder was mixed with 2%

P.V.A. binder and by die hydroxilic pressure pressed into pellets of thickness 1 cm and rings of outer diameter = 1.5 cm, inner diameter 1.0 cm and thickness = 0.3 cm.

These samples were presintered at 700^oC for 3 hours followed by slow cooling in furnanace. The pellets close coated with silver paste to provide electrical contacts and rings were wound with about 50 turns on enameled copper wire to from torroids.

Dielectric constant, dielectric loss, initial permeability and loss factor were measured by using Agilent Technologies 4285A Precision LCR Meter upto 30MHzX-ray diffraction measurements were taken on a Rigaku Geiger Flex 3 kW diffractometer using CuKα source.

III. RESULT AND DISCUSSION

X-Ray diffraction patterns of Mn-Zn ferrites having chemical composition MnxZn1-x Fe2O4 (x = 0.3, 0.4, 0.5) where obtained as shown in figure 1.These figures shows

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the position and relative intensities of the various X-Ray diffraction peaks.

All the diffraction patterns showed characteristics lines of spinel structure ferrite and no extra lines were observed, which indicate that all the samples had single phase spinel structure. The average grain particle size has been evaluated from (FWHM) i.e. full width at half maximum of the reflection of maximum intensity in the XRD pattern using scherr’s formula [12-13].

d = K λ/Bcosθ……….(1) where B² = B²M-B²S

d is the particle size in A⁰, K is the shape factor , λ is the X- ray wavelength (1.54 A0), BM & BSare measured peak broadening and instrumental broadening in radian respectively. The calculated average particle sizes were found to be around 1μm.

20 30 40 50 60

Mn_0.5Zn_0.5Fe₂O₄ (sintered at 700^oC)

2

511

422

400

222

311

220

Mn_0.4Zn_0.6Fe₂O₄ (sintered at 700^OC)

Intensity (arb.unit) 111

Mn_0.3Zn_0.7Fe₂O₄ (sintered at 700^OC)

Fig. 1 X-ray diffraction of MnxZn1-xFe2O4 (x = 0.3, 0.4 and 0.5) ferrite sintered at 700^oC.

Initial Permeability

The variation of initial permeability with frequency The observed variation of initial permeability (i) as a function of frequency of the applied field in the frequency range from 75 KHz to 30 MHz is shown in figure for the Mgx Zn1-x F2O4 (X=0.3, 0.4, 0.5) ferrite sample.

The initial permeability remains almost constant up to 10⁶ Hz and then decreases upto 10⁷ Hz. A significant rise is observed at high frequencies.

The variation of initial permeability with frequency can be understood on the basis of Globus model [14-17].

According to this model, relaxation character, (_i1)²fr = constant, ……….. where I is the static initial permeability and fr is the relaxation frequency. It follows from this equation that the dispersion frequency is expected to be lower for specimen of higher permeability.

10⁵ 10⁶ 10⁷

250 300 350 400 450 500

Frequency (Hz) Mn_0.5Zn_0.5Fe₂O₄ Mn_0.4Zn_0.6Fe₂O₄ Mn_0.3Zn_0.7Fe₂O₄

Permeability ()

Initial permeability is dependent on many parameters such as stoichiometry, grain structure, composition, impurity contents, saturation magnetization, magnetostriction, crystal anisotropy and porosity. High permeability is favoured by large grain size, high saturation magnetization, low porosity, low crystal anisotropy, low magnetostriction and high purity of the material. Since at nano level, grains have a single domain configuration, therefore grain structure is not contributing to the high initial permeability. As the initial permeability is sensitive to many other parameters, it is difficult to draw specific conclusion as to which other factors are dominating here.

The variation of the tan_ with frequency is shown in figure.

10⁵ 10⁶ 10⁷

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Mn_0.5Zn_0.5Fe₂O₄ Mn_0.4Zn_0.6Fe₂O₄ Mn_0.3Zn_0.7Fe₂O₄

Frequency (Hz)

Magnetic loss

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Variation of permeability loss factor (tan  ) with frequency

As can be seen that permeability loss factor decreases rapidly upto frequency 10⁶ Hz and then a slow decrease upto 10⁷ Hz in each sample. And then at higher frequency the permeability loss factor increases.

These values are about the same and in some cases are of an order or magnitude lower than those for the specimens prepared by the soft chemical route . The variation of tan with frequency showed identical behaviour all the specimens as proposed by Globus. This is the normal behaviour and also observed by other workers[18-19].

Dielectric constant :- The variation of dielectric constant

‘’ for Mn Zn_1-x Fe2O4nanoferrites was studied as a function of frequency. Frequency was varied from 75 KHZ to 30 MHZ. The results for these measurements are shown in fig.

10⁵ 10⁶ 10⁷

40 41 42 43 44 45 46 47 48 49 50

Dielectric constant ()

Frequency (Hz) Mn_0.5Zn_0.5Fe₂O₄ Mn_0.4Zn_0.6Fe₂O₄ Mn_0.3Zn_0.7Fe₂O₄

The value of dielectric constant of Mn-Zn nanoferrite as a function of frequency shows that for each sample dielectric constant decreases slowly upto 10⁶ Hz. A increase in dielectric constant was found above 10⁶ Hz.

The value of dielectric for Mn0.3 Zn0.7 Fe2O4 does not increased much in comparison to others.

The variation of dielectric constant reveals the dispersion due to Maxwell-Wanger [20-21] interfacial polarization in agreement with Koops phenomenological theory [22].

Increase in dielectric constant with frequency can a given as, IWauchi [23] pointed out that there is a strong correlation between conduction mechanism & the dielectric behavior of ferrites. Variation of dielectric loss factor (Tan) with frequency as shown in figure for Mnx

Zn1-x Fe2O4 (x= 0.3, 0.4, 0.5) ferrite sample. Frequency was varied from 75 KHZ to 30 MHZ.

10⁵ 10⁶ 10⁷

0.0 0.1 0.2 0.3 0.4

Dielectric loss

Frequency (Hz)

Mn_0.5Zn_0.5Fe₂O₄ Mn_0.4Zn_0.6Fe₂O₄ Mn_0.3Zn_0.7Fe₂O₄

The electric loss factor has been observed to be high at low frequencies which decreases to low values at high frequencies. But dielectric loss factor for Mn0.5 Zn0.5

Fe2O4 does not show much variations. This could be understand with the help of koops phenomenological model [22]. A quantities description of this increase in Tan can be given as, I wachi [23] point out that there is strong correlation between conducting mechanism and the dielectric behaviour of ferrites.

IV. CONCLUSION

We are successful in synthesizing high permeability ferrites in our laboratory by oxalate precipitation method, which could be used from low frequency to high frequency applications, data storage devices, inductors, cores of transformers etc.

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