Structural and Magnetic Properties of Nickel Substituted Mg Ferrites

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Available online at www.sciencedirect.com Procedia Engineering00 (2017) 000–000

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Procedia Engineering 215 (2017) 9–16

9th International International Conference Conference on on Materials Materials for for Advanced Advanced Technologies Technologies(ICMAT (ICMAT2017) 2017) 9th

Structural and Magnetic Properties of Nickel Substituted Mg Ferrites Pradeep Chavan1, L R Naik1*, Geeta Chavan2, P B Belavi3 and R K Kotnala4 1 1Department

Department of studies in physics, Karnatak university dharwad-580003, India

2 2Department

Department of studies in physics, Karnatak Science College, dharwad-580003, India

3 3Department

Department of studies in physics, Gogte institute of Technology, Belgaumi-590008, India 4 4National

National Physical Laboratory, K. S. Krishnan Marg, Pusa, New Delhi-110012, India

Abstract Polycrystalline ferrites with general formula NixxMg1-x 1-xFe22O44 (0.0 ≤ x≤ 0.5) were synthesized by solid state reaction method. The existence of cubic spinel structure of ferrites was confirmed by X-ray diffraction (XRD) measurement which belongs to the space 77 group of Fd3m 3m - Ohh . Crystallite size of ferrites was estimated by using Debye-�cherer �orm�la� it �aries �rom ��0 nm to �.0� �m. The lattice constant, interplanar distances and miller indices were estimated by using X-ray diffraction measurement. The lattice constant increases with increase in Ni content. Porosity of ferrites was estimated by using Hendricks and Adams method; it is found to increase with increase in Ni content and maximum porosity 22.4% was observed for Ni 0.5 0.5Mg0.5 0.5Fe22O44 ferrites. The dielectric constant decreases with increase in frequency shows dielectric dispersion behavior which is predicted by MaxwellWagner type interfacial polarization and is in good agreement with Koops phenomenological theory. AC conductivity increases with increase in frequency shows small polarons type of conduction mechanism. The magnetic properties of ferrites were studied by using M-H hysteresis loop and measured saturation magnetization and magnetic moment of the ferrites. © 2017 The Authors. Published by Elsevier Ltd. © 2017 The Authors. Published by Elsevier Ltd. of the scientific committee of Symposium 2017 ICMAT. Selection and/or peer-review under responsibility Selection and/or peer-review under responsibility of the scientific committee of Symposium 2017 ICMAT. Keywords: Debye-Scherer formula, space group, Hendricks and Adams method, M-H hysteresis loop and magnetic moment.

* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address:[email protected] 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the scientific committee of Symposium 2017 ICMAT.

1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the scientific committee of Symposium 2017 ICMAT. 10.1016/j.proeng.2017.12.147

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1. Introduction The invention of ferrite materials before 20th century and subsequent theory of ferrimagnetism pioneered by Louis Neel resulted in a surge of research activities [1]. This made possible to discover the ferrite materials for various applications in science and technology. In the past few decades, study of ferrites has played an important role in electronic technology and multiferroic materials are being explored extensively in technological field [2]. Polycrystalline ferrites are being considered as the most significant materials in scientific point of view owing to their wide range of applications especially in high frequency devices and biomedical applications [3]. Ferrite materials are most applicable in electronics, communication sciences and electrical technology, heterogeneous catalysis, sensor technology, microwave control components, isolators, circulators, phase shifters and high density recording devices, etc [4]. Magnesium ferrite is a porous assembly of n-type oxides used for the development of humidity sensors. The magnesium ferrites applicable in thermal coagulation therapy were tumors are locally heated by the use of alternating magnetic field [5]. Dielectric materials are electrical insulators in which an electrostatic field can exist. These dielectric materials have an ability to store and dissipate electrical energy when subjected to applied electromagnetic field. The most important property of dielectric materials is their ability to be polarized under the action of external electric field. Generally, electrical properties mainly depend upon method of preparation, chemical composition, sintering time, sintering temperature and grain size [6]. The magnetization is an important property of magnetic materials to decide their applications in various fields [7]. The choice of ferrites for particular application depends on magnetic parameters such as saturation magnetization, magnetic moment, coercivity and retentivity etc. are greatly influenced by porosity, grain size and microstructure of the samples [8]. The present work aimed at the synthesis and study of structural and magnetic properties of Ni substituted magnesium ferrites have been discussed. 2. Experimental details Polycrystalline ferrites having the chemical composition NixMg1-xFe2O4 in which x varies from 0.0 to 0.5 were synthesized by solid state reaction method. The high purity analytical reagent grade metal oxides of fine grain powders like NiO, MgO, and Fe2O3 were used as the starting material for the preparation. These metal oxides are weighed in required molar proportion according to the stoichiometry. The weighed metal oxides are grinded in acetone medium continuously of about 4 to 5 hrs in a planetary agate mortar to obtain the homogenous mixture of the oxides. The long duration of grinding also helps in decreasing the grain size. The mixture was presintered at 800°C for 8 hrs in muffle furnace in air medium and cooled to room temperature. The fine grinded powder was mixed with polyvinyl alcohol (2% solution) which acts as a binding agent and it is further pressed into the pellet form of 10 mm diameter and 2-3 mm thickness by applying pressure of 7 tons/cm2 for 5 min using hydraulic KBr press. These pellets were kept in programmable furnace for final sintering at 1150 oC for 12 hrs and cooled to room temperature. These samples further used for various characterization and study of several properties. X-ray diffraction (XRD) measurement was characterized by using X-ray Diffractometer (Model: Rigaku Miniflex, BITS Pilani, Goa) with Cu-.ĮUDGLDWLRQȜ  Å). The magnetic properties of ferrites were studied by using vibrating sample magnetometer (VSM) (Model: 735, Lakeshore, National Physical Laboratory, New Delhi). 3. Results and Discussion 3.1. X-ray diffraction (XRD) Measurement X- ray diffraction (XRD) pattern of single phase cubic spinel structure of ferrites is shown in figure 1. All peaks in X- ray diffraction (XRD) pattern were identified and indexed with the help of American Society for Testing and Materials (ASTM) data. The prominent peak (3 1 1) observed in all ferrite samples confirmed the existence of cubic spinel structure of ferrites without any impurities [9]. The crystallite size of ferrites was estimated from the broadening of high intense diffraction peak i.e. (3 1 1) by using the Debye-Scherer equation as follows [10]: 𝐾𝐾𝐾𝐾𝐾 (1) �� �𝐾���𝐾�𝐾



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Where K is the constant (i.e. K = 0.9), � is the wavelength of X-ray, β is the full width half maximum (FWHM) and θ is Bragg’s angle. The estimated values of crystallite size, lattice constant and porosity of the ferrites were listed in table 1. It is observed that the crystallite size increases with increase in Ni content; it varies from 93� nm to ���� �m� �rom the table 1, it is observed that the lattice constant increases with increase in Ni content in ferrites; it was due to the difference between ionic radii of the component ions in ferrite system.

Fig 1 Graph of X-ray diffraction pattern of NixMg1-xFe2O4 ferrites. The ionic radii of Mg2+ ions (0.072 nm) are slightly greater than Ni2+ (0.069 nm) and Fe3+ ions (0.0645 nm), this gives the evidence for the variation of lattice constant with increase in Ni 2+ ions in ferrites [11]. The porosity of ferrites was estimated by using Hendricks and Adams method [12]: ���������� =

Where dx =X-ray density, da = Actual density. x content

0.0 0.1 0.2 0.3 0.4 0.5

��𝑥𝑥 ��𝑎𝑎 � �𝑥𝑥

× ���

(2)

Table 1. Lattice constant, X-ray density, % porosity, particle size. Particle size Lattice Constant X-ray Density % (Å) (dx) Porosity 8.332 8.344 8.363 8.366 8.371 8.375

4.5504 4.6041 4.6899 4.7795 4.8861 4.9838

19.0 19.2 20.9 21.4 21.9 22.4

930nm 981nm 982nm 986nm ���3�m �����m

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Porosity is the inherent property of ceramics prepared by sintering and powder pressing. High rate of sintering with small crystallite size reduces the porosity appreciably. The porosity of ferrites increases with increase of Ni content in ferrites and maximum porosity 22.4% was observed for Ni 0.5Mg0.5Fe2O4 ferrites (Table 1). The pores materials provides insulating path to the electrons resulting in the increase of resistivity [13]. 3.2. Dielectric properties of ferrites The variation of dielectric constant with respect to frequency is shown in figure 2. It is observed that the dielectric constant decreases with increase in frequency shows dielectric dispersion behavior. It is because of above certain frequency, electronic exchange between Fe3+ and Fe2+ ions does not follow the applied field. This behavior observed was due to the interfacial polarization predicted by Maxwell–Wagner [14]. According to Debye theory, the variation of dielectric constant with respect to frequency was due to the opposition of orientation of polar molecules in applied field by the effect of thermal agitation and molecular interactions. According to “Maxwell–Wagner model”, the dielectric constant of ferrites consists of two layers. The first layer consists of large grains of well conducting materials that are separated by the second layer and second layer is a thin layer of grain boundaries of relatively poorly conducting substance [15]. The Ni 3+↔Ni2++e+ gives the holes concentration in octahedral sites which can produce the local displacement in the opposite direction of applied field. Addition of Ni ions reduces the iron ions in B-site, which is mainly responsible for space charge polarization and hopping exchange between the localized states [16]. Therefore, the increase of Ni content in Mg ferrites causes the decrease in polarization which accomplished by the decrease of dielectric constant. Koops theory explained the effect of grain boundaries predominant at the lower frequencies of ferrites [17].

Fig 2. Dielectric dispersion graph of nickel substituted Mg ferrites (0.0 ≤ x≤ 0.5).



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Fig 3. Dielectric loss tangent graph of Ni substituted Mg ferrites (0.0 ≤ x≤ 0.5). The dielectric loss tangent as a function of frequency of Ni substituted Mg ferrites (0.0 ≤ x≤ 0.5) is shown in figure 3. The electronic exchange between Fe3+↔Fe2+ and transfer of holes between Ni2+ ↔ Ni3+ in octahedral sites are responsible ions for such behavior. Furthermore, the variable frequencies of localized charge carriers are almost equal to that of applied AC electric field [18]. Frequency dependent AC conductivity of ferrites is shown in figure 4. The variation of AC conductivity with frequency explains to understand the behavior of thermally activated conduction mechanism and the type of polarons hopping responsible for conduction of electrons in the ferrites. AC conductivity was estimated by using the values of dielectric constant and dielectric loss factor with the relation as follows [11], (3) 𝜎𝜎�� � �′�0 ������

Where �� is dielectric constant, �0 is Permittivity of free space, ω is Frequency of applied field and tan� is dielectric loss tangent. There are two types of polarons hopping mechanisms in ferrites namely small polarons and large polarons. The increase of AC conductivity with increase in frequency was due to the small polaron model, whereas decrease of AC conductivity with increase in frequency was due to large polaron hopping model [19]. The polaron hopping type of conduction mechanism was explained in detail by Austin Mott and Appel [20]. Alder and Feinleib also explained that the direct frequency dependent conduction mechanism was due to the small polaron hopping type of conduction electrons in ferrites [21]. The figure 4 shows that AC conductivity increases with increase in frequency indicates small polaron hopping type of conduction mechanism.

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Fig 4 AC conductivity measurement of Ni substituted Mg ferrites (0.0 ≤ x≤ 0.5). 3.3. Magnetic Properties Magnetic properties of ferrite materials characterized by M-H hysteresis loop which gives the magnetic behavior when excited by applied magnetic field. The magnetic moment of ferrites estimated by using the relation: �B = [

M

5585

] Ms

(4)

Where M is the molecular weight, Ms is the saturation magnetization. M-H Hysteresis loop of Ni substituted magnesium ferrites at room temperature are shown in figure 5. The parameters such as saturation magnetization (Ms), magnetic moment, coercivity (Hc), retentivity (Mr) and ratio of remanent magnetization to saturation magnetization (Mr/Ms) for all composition of ferrite samples are listed in table 2. From figure.5, it is observed that the saturation magnetization and magnetic moment increases with increase in Ni content in magnesium ferrites obey Neels two sublattices model [22]. The ratio of (Mr/Ms) gives a small value that belongs to the presence of multidomain (MD) particles. In magnesium ferrite, a super exchange interaction via oxygen ions results in high anisotropy layer. This often occurs when two magnetic ions separated by nonmagnetic ions such as oxygen. Magnetic ions have magnetic interaction mediated by electrons in their common nonmagnetic neighbors which is more important than their direct exchange interactions referred to as super exchange interaction. The presence of impurity atoms at the surface leads to the breakage of super exchange bonds between magnetic cations and results in large surface spin distortion [23].



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Fig 5. M-H Hysteresis loop of Ni doped Mg ferrites (0.0 ≤ x≤ 0.5). The magnetic anisotropy is directly proportional to the coercive force and a large variation in coercive force observed with increase in Ni content. The large increase in magnetic anisotropy for higher Ni content suggests that higher amount of Ni tends to occupy B-site [10]. The increase of saturation magnetization and magnetic moment with increase of Ni content was due to the surface spin effect and cation distribution on tetrahedral and octahedral sites. Ni2+ ions strongly occupy tetrahedral site [24, 25], while Mg2+ ions occupy octahedral site and Fe3+ ions occupies both tetrahedral and octahedral sites. However, small values of (Mr/Ms) and coercivity (Hc) suggests that the existence of multidomain (MD) particles in all samples [26]. Table 2. Saturation magnetization (Ms ), Magnetic moment (�B ), Retentivity (Mr), Coercivity (Hc) and ratio of remnant magnetization to saturation magnetization (M r/Ms). X Content

𝑀𝑀𝑠𝑠

𝜇𝜇�

Retentivity

Coercivity

(Mr)

(Hc)

Mr/Ms

0.0

29.396

1.0526

1.0793

0.02241

0.036716

0.1

19.289

0.7025

0.9586

0.02262

0.049697

0.2

27.992

1.0368

2.0425

0.00259

0.072967

0.3

34.935

1.3155

4.2874

0.04498

0.122725

0.4

35.533

1.3598

3.1170

0.00836

0.087721

0.5

36.688

1.4266

3.3888

0.04034

0.092368

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Conclusion Ni substituted magnesium ferrites (0.0 ≤ x≤ 0.5) successfully prepared by solid state reaction method and confirmed the existence of cubic spinel structure of ferrites with the help of X-ray diffraction measurement which belongs to the space group of Fd3m-Oh7. The decrease of dielectric constant with increase in frequency shows the dielectric dispersion behavior. AC conductivity increases with increase in Ni content was due to small polaron model. The saturation magnetization and magnetic moment increases with increase in Ni content, the maximum magnetic moment 1.4266 kOe was observed for Ni0.5Mg0.5Fe2O4 ferrites. The maximum saturation magnetization 36.688 emu/gm was observed for Ni0.5Mg0.5Fe2O4 ferrites. Acknowledgement Author (Pradeep Chavan) thankful to Karnatak University, Dharwad for providing financial support under UGC-UPE fellowship throughout my research work. The authors extend their gratitude to Dr Jyothi Shah, NPL New Delhi, for providing VSM measurement at their laboratory. Author (Pradeep Chavan) extend his gratitude to UGC for awarding Rajiv Gandhi National Fellowship for the year 2016-17. References [1] P. B. Belavi, G. N. Chavan, L. R. Naik, R. Somashekar, R. K. Kotnala, Mater. Chem. Phys. 132 (2012) 138. [2] R.K. Kotnala et al. / Sensors and Actuators B. 129 (2008) 909. [3] V. Sepelak et al. / J. Magn. Magn. Mater. 316 (2007) e764. [4] K.A. Mohammed et al. / Physica B. 407 (2012) 795. [5] Ahmad, Tokeer, and Irfan H. Lone. Mater. Chem. Phys. 202 (2017) 50. [6] Ebtesam E. Ateia, E. Takla, Amira T. Mohamed, A.T, Appl. Phys. A 123 (2017) 631. [7] A. Loganathan, K. Kumar, Appl. Nanosci. 6 (2016) 629. [8] U.R. Ghodake, N.D. Chaudhari, R.C. Kambale, J.Y. Patil, S.S. Suryavanshi, J. Magn. Magn. Mater. (2016). [9] K. B. Modi, M. K. Rangolia, M. C. Chhantbar and H. H. Joshi/ J. Mater. Sci. 41 (2006) 7308. [10] Pradeep Chavan, L. R. Naik, P. B. Belavi, Geeta Chavan, C. K. Ramesha & R. K. Kotnala, J. Elect. Mater. 46 (2017) 188. [11] Pradeep Chavan, L.R. Naik, P.B. Belavi, G.N. Chavan, R.K. Kotnala, J. All. Compds. 694 (2017) 607. [12] A.I. Ahmed, M.A. Siddig, A.A. Mirghni, M.I. Omer, A.A. Elbadawi, Sci. Res. Publ. 4 (2015) 45. [13] Pradeep. Chavan and L. R. Naik, Int. J. Engg. Sci. Res. 6(1) (2016) 29. [14] L. J. Berchmans et al. / J. Magn. Magn. Mater. 279 (2004) 103. [15] K. Wagner, Ann. Phys 40 (1913) 817. [17] Pradeep Chavan and L. R. Naik, Phys. Status Solidi A, 1700077 (2017) 1. [16] A. Ghasemi, J. Alloys. Compd. 645 (2015) 467. [18] N. Rezlescu, E. Rezlescu, Phys. Stat. Sol (a). 23 (1974) 575. [19] Z. P. Niu, Y. Wang, F. S. Li, J Mater Sci. 41 (2006) 5726. [20] H N Nathani, S. Gubbala and R D K Misra, Mater. Sci.Eng. B (2005)121. [21] M. Chaitanya Varma, GSVRK Choudary, A. Mahesh Kumar, and K. H. Rao, Hindawi Publishing Corporation, Physics Research International. 2014, Article ID 579745. [22] S S Bellad, R B Pujar & B K Chougale, Matter Chem Phys. 52 (1998) 166. [23] P. B. Belavi and L. R. Naik, Physics of Semiconductor Devices, Environmental Sci. and Eng. (2014) 659. [24] S. A. Patil, V. C. Mahajan, A. K. Gatge, S. D. Lotake, Mater. Chem. Phys. 57 (1998)86. [25] O. M. Hemeda, M. M. Barakat, J. Magn. Magn. Mater. 223 (2001) 127. [26] Bammannavar et al/ Indian Journal of Engineering and Materials Sciences. 14 (2007) 381.