International Journal of Conceptions on Computing and Information Technology Vol. 3, Issue. 1, April’ 2015; ISSN: 2345 - 9808

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Structural and dielectric properties of Indium substituted Ni-Cu-Zn ferrites

M Raghasudha Dept. of Chemistry

JayaPrakash Narayan College of Engineering Mahabubnagar, Telangana, India

raghasudha_m@yahoo.co.in

P Veerasomaiah Dept. of Chemistry, UCS

Osmania University Hyderabad, Telangana, India vs_puppala@rediffmail.com

Abstract— Nanocrystalline Ni0.5Cu0.25Zn0.25Fe2-xInxO4 ferrites of chemical composition with Indium content 0.0≤x≤0.4 were prepared by citrate-gel auto-combustion method. Structural characterization of prepared ferrite samples was carried out by X-ray diffraction analysis (XRD) and Scanning electron microscopy (SEM). XRD analysis confirms the formation of single phased cubic spinel structure of the samples with a crystallite size ranging from 25-34nm. Surface morphology was studied by SEM analysis. High temperature dielectric measurements were carried out using LCR meter with which the dielectric parameters such as dielectric constant (ε′) and dielectric loss (tan δ) were measured at different frequencies ranging from 100 Hz to 5 MHz in the temperature range of 50 -3000C. It is observed that ε′ and tan δ of the ferrites under investigation were increased with increase in temperature for all the selected frequencies. This frequency dependent phenomenon may be attributed to the interfacial polarization in the ferrite samples.

Keywords- Ferrites; Citrate-gel method; XRD; SEM; Dielectric parameters

I. INTRODUCTION The spinel magnetic ferrites have generated considerable

interest among the researchers all across the world, due to their unique and versatile properties [1]. Spinel ferrites are technologically significant materials as they possess exceptional electrical and magnetic properties which make them appropriate for high frequency applications in the field of telecommunication [2]. Owing to high resistivity and low eddy current losses at high frequency, nano ferrites serve as desirable materials for microwave devices [3]. The electrical properties of ferrites are dependent on the microstructure, chemical composition and synthesis technique [4]. Several methods are used for synthesizing nanosized spinel ferrites such as co-precipitation, sol-gel, micro-emulsion, hydrothermal, and reverse micelle methods [5,6].

Ni ferrite is the most suitable one in which the magnetic and electrical properties are affected by the substituent [7]. Assuming the fact that In3+ substitution in NiCuZn ferrites for Fe3+ results in change in structural and electrical properties, the author has investigated and reported the structural and dielectric behavior of In substituted NiCuZn ferrites. The present paper reports the high temperature dielectric study of

Indium substituted NiCuZn ferrites at different frequencies ranging from 100 Hz to 5 MHz.

II. EXPERIMENTAL

A. Materials and Synthesis Ni0.5Cu0.25Zn0.25Fe2−xInxO4 (0.0≤x≤0.4)

nanocrystalline ferrite were synthesized using Ni(NO3)2.6H2O, Cu(NO3)2.6H2O, Zn(NO3)2.6H2O, In(NO3)3.9H2O, C6H8O7H2O and Fe(NO3)3.9H2O as starting materials by citrate gel auto combustion method. The detailed procedure for the synthesis of spinel nanoferrites by Citrate-gel auto-combustion method was clearly mentioned in our earlier publication [8]. Figure 1 shows the simple flow chart for the synthesis of Ni-Cu-Zn-In spinel nano ferrite.

Fig. 1: Synthesis of Ni-Cu-Zn-In nano ferrites by citrate-gel method

B. Characterization The structural characterization of the prepared nano

ferrites was performed by X-ray diffraction analysis and Scanning Electron microscopic analysis. XRD analysis confirms the phase formation and SEM analysis reveals the structural morphology.

METAL NITRATE SOLUTI

International Journal of Conceptions on Computing and Information Technology Vol. 3, Issue. 1, April’ 2015; ISSN: 2345 - 9808

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The dielectric properties of the prepared nanoferrites were measured using LCR meter in the temperature range of 50 to 3000C at different frequencies ranging from 100 Hz to 5 MHz. Dielectric parameters such as dielectric constant (ε׳), dielectric loss tangent (tan δ) were measured using LCR meter in the specified range of temperature and frequency.

III. RESULTS AND DISCUSSION

A. XRD Analysis X-ray diffraction patterns obtained by XRD analysis were shown in figure 2 which confirms the formation of single phased cubic spinel structure of the ferrites as compared to the standard XRD patterns with JCPDS No. 48-0489. The particle size was calculated using Sherrer’s formula (8) and was found to be in the range of 25-34nm as shown in table.1

Figure 2. XRD patterns of NiCuZnIn ferrites

TABLE 1. PARTICLE SIZE OF Ni-Cu-Zn-In FERRITEs

B. SEM Analysis The SEM images of various compositions of NiCuZnIn ferrites were shown in the figure 3. The SEM images reveal that the particles are spherical in shape and are agglomared in nature.

Figure 3. SEM Images of Ni0.5Cu0.25Zn0.25Fe2−xInxO4 (0.0≤x≤0.4) nanoferrites

C. Dielectric measurements The dielectric parameters (ε׳ and tanδ) were found to be dependent on variation of external factors such as temperature and frequency. The variation of dielectric constant and dielectric loss tangent in the temperature range of 50 to 3000C at different frequencies ranging from 100 Hz to 5 MHz was investigated. a. Variation of dielectric constant with frequency and temperature Figure 4 indicates the variation of dielectric constant of Ni0.5Cu0.25Zn0.25Fe2−xInxO4 nanoferrites with frequency at different temperatures for various concentrations of Indium from x=0.0 to x=0.4.

Ferrite composition Particle size(nm)

Ni0.5Cu0.25Zn0.25Fe2O4 25

Ni0.5Cu0.25Zn0.25Fe1.9In0.1O4 28

Ni0.5Cu0.25Zn0.25Fe1.8In0.2O4 29

Ni0.5Cu0.25Zn0.25Fe1.7In0.3O4 31

Ni0.5Cu0.25Zn0.25Fe1.6In0.4O4 34

X=0.2

X=0.1

X=0.0

X=0.3

X=0.4

International Journal of Conceptions on Computing and Information Technology Vol. 3, Issue. 1, April’ 2015; ISSN: 2345 - 9808

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Figure 4. Variation of log of real dielectric constant () with frequency at

selected temperatures for Ni0.5Cu0.25Zn0.25Fe2−xInxO4 (0.0≤x≤0.4) nanoferrites

From the figure, it is clear that the dielectric constant fall rapidly at lower frequency showing dispersion where as the decrease is less at higher frequency for all temperatures All the samples showed this dispersion at low frequency range at all temperatures, which is due to Maxwell-Wagner polarization [9, 10]. This dielectric behavior of ferrites under investigation can be explained by Koops theory. According to the theory, dielectric material is assumed to be made up of well conducting grains separated by non-conducting grain boundaries. The grain boundaries are more effective at low frequencies whereas the grains are more effective at the higher frequencies. Figure 5 shows the variation of dielectric constant with temperature at selected frequencies for all the samples Ni0.5Cu0.25Zn0.25Fe2−xInxO4 (0.0≤x≤0.4). From the figure, it is observed that dielectric constant of all the samples at selected

frequencies was increased with increase in temperature. This is because, the charge carriers (electrons) are thermally activated with increase in temperature of the sample resulting in an increase in electron exchange interaction. This fact makes the dielectric constant values to increase. From the figure, it is also clear that the increase in dielectric constant with increase in temperature is appreciable at lower frequency but it is very less (almost constant) at higher frequency.

Figure 5. Variation of log of real dielectric constant () with temperature at selected frequencies for Ni0.5Cu0.25Zn0.25Fe2−xInxO4 (0.0≤x≤0.4) nanoferrites

b. Variation of dielectric loss tangent with frequency Figure 6 shows the variation of dielectric loss tangent with frequency at selected temperatures for all the samples Ni0.5Cu0.25Zn0.25Fe2−xInxO4 (0.0≤x≤0.4). The figure reveals that the dielectric loss tangent decrease with frequency.The behavior of dielectric loss tangent (tanδ) with frequency is same as that of dielectric constant. This is because, the jumping frequency of the charge carriers cannot follow the frequency of the applied field beyond certain frequency. At higher frequency range all the compositions show low dielectric loss for all temperatures as evident from the figure.

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0.1

1

10

0.01

0.1

1

0.01

0.1

1

10

0.01

0.1

1

1 2 3 4 5 6 70.01

0.1

1

x = 0.1

RT 50 0C 100 0C 150 0C 200 0C 250 0C 300 0C

x = 0.0

Tan

x = 0.2

Tan

x = 0.3

Log f (Hz)

x = 0.4

Tan

Log f (Hz) Figure 6. Variation of loss tangent (tan) with frequency at selected temperatures for Ni0.5Cu0.25Zn0.25Fe2−xInxO4 (0.0≤x≤0.4) nanoferrites

IV. CONCLUSION Ni0.5Cu0.25Zn0.25Fe2-xInxO4 (0.0≤x≤0.4) nanoferrites were

synthesized using Citrate-gel method. The XRD patterns confirmed the formation of single phased cubic spinel ferrites with an average particle size of 25-34nm. SEM analysis reveals that the shape of the particle is spherical. The dielectric constant (ε′) and dielectric loss tangent (tan δ) showed a decreasing tendency with increase in frequency at selected temperatures for all compositions. The decrease is more at

lower frequency and show almost constant performance at higher frequency. The dielectric constant and loss tangent show increasing trend with increase in temperature at all frequencies. The low dielectric loss values of the NiCuZnIn ferrites in high frequency range at all temperatures make them desirable for high frequency microwave applications.

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ferrites,” Advances in Nanoscience and Nano Tech, A. Sharma, Ed., NISCAIR, 2003

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[3] J. Kulikowski, “Soft magnetic ferrites-Development or stagnation?” J. Magn. Magn. Mater. 41 (1984) 56-62.

[4] A. Verma, R. Chatterjee, “Effect of zinc concentration on the structural, electrical and magnetic properties of mixed Mn–Zn and Ni–Zn ferrites synthesized by the citrate precursor technique” J. Magn. Magn. Mater. Vol. 306, 2006, PP. 313-320.

[5] E.Veena Gopalan, I. A. Al-Omari, K. A.Malini et al., “Impact of zinc substitution on the structural and magnetic properties of chemically derived nanosized manganese zinc mixed ferrites”, J Magn. Magn. Mater. Vol. 321, 2009, PP. 1092-1099.

[6] M. Srivastava, S.Chaubey, A.K.Ojha, “Investigation on size dependent structural and magnetic behavior of nickel ferrite nanoparticles prepared by sol–gel and hydrothermal methods”, Mater. Chem. Phys. Vol. 118, 2009, PP. 174-180.

[7] P.K. Roy, Bibhuti B. Nayak, J. Bera, “Study on electro-magnetic properties of La substituted Ni–Cu–Zn ferrite synthesized by auto-combustion method”, J. Magn. Magn. Mater. Vol. 320, 2008, PP. 1128-1132.

[8] M. Raghasudha, D. Ravinder, P. Veerasomaiah, “Characterization of nano-structured magnesium-chromium ferrites synthesized by citrate-gel auto combustion method”, Adv. Mat. Lett. Vol. 4, 2013, PP. 910-916.

[9] J. C. Maxwell, A Treatise on Electricity and Magnetism, Oxford University Press, New York, Vol.1, 1973, PP. 828.

[10] K. W. Wagner, Zur Theorie der Unvollkommenen Dielektrika, Annalen der Physik, Vol. 40, 1913, PP. 817.