Structural, morphological and electrical properties of Sn-substituted Ni-Zn ferrites synthesized by double sintering technique

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Highlights

  • Sn-substituted Ni-Zn ferrites with cubic spinel structure have been synthesized.

  • ath is calculated and well compared with aexpt.

  • Dielectric unusual behavior has been successfully explained by the Rezlescu model.

  • Long τ (ns) is determined, can be utilized for memory and spintronics devices.

Abstract

The Sn-substituted Ni-Zn ferrites, (0.0≤x≤0.30), have been synthesized by the standard double sintering technique from the oxide nanopowders of Ni, Zn, Fe and Sn. The structural and electrical properties have been investigated by the X-ray diffraction (XRD), scanning electron microscopy (SEM), DC resistivity and dielectric measurements. From XRD data, the single cubic spinel phase has been confirmed for x≤0.1, whereas for x>0.1 an extra intermediate phase has been detected along with the cubic spinel phase of Ni-Zn ferrite. The grain size is increased due to Sn substitution in Ni-Zn ferrites. DC resistivity as a function of temperature has been measured by two probe method. The semiconducting nature has been found operative in the samples. The DC resistivity was found to decrease whilst the dielectric constant increased with increasing Sn content in Ni-Zn ferrites. The unusual behavior of the dielectric loss factor of the ferrites was explained by the Rezlescu model. The electrical relaxation of the ferrites has been studied in terms of electric modulus formalism and the time for dielectric relaxation was calculated. The contribution of grain resistance has been studied from the Cole-Cole plot. The suitability to use the as prepared samples in the miniaturized memory devices based capacitive components or energy storage principles are confirmed from the values of dielectric constant.

Introduction

In recent years, the spinel ferrites belong to AB2O4 structure having A-site and B-site have drawn huge attention due to their fascinating properties to meet the requirements in various applications. The Ni-Zn ferrites have been found to be the most versatile ferrites systems from the perspective of their technological application because of its high electrical resistivity, high permeability, compositional stability and low eddy current losses [1], [2], [3], [4], [5], especially ideal for high frequency applications. The outstanding combination of these properties makes them attractive for potential applications in diverse field. The research and application of magnetic materials have been developed considerably in the few past decades. In order to discover new types of ferrites and develop their properties scientific community have also paid their significant attention. The properties of Ni-Zn ferrites can be altered by changing chemical composition, preparation methods, sintering temperature (Ts) and impurity element or levels. The basic properties of Ni-Zn ferrites have been improved by changing the preparation techniques, chemical composition, doping ions or levels having different valence states, etc. [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32]. But most of them dealt with the magnetic properties of doped Ni-Zn ferrite. Researchers have also reported the structural, electrical and/or dielectric properties of doped Ni-Zn ferrite. Recently, many researchers reported the structural, magnetic and electrical properties of Ni-Zn ferrite and/or substituted Ni-Zn ferrites in bulk [17], [18], [23], [24], [25], [30], [31], [32] and nano forms [20], [26], [27], [28].

The tetravalent ions such as Ti4+, Sn4+ and Si4+ substitution have greatly influenced the properties Ni-Zn ferrites [33]. Details investigation on Ti4+ doping in Ni-Zn ferrite system has been carried out [6], [7], [8], [12], [18] while introduction of Sn4+ has attracted less attention [8], [9], [10]. But they have mainly focused on the magnetic properties of Sn-substituted Ni-Zn ferrites, where Sn is substituted for Fe. The materials with high dielectric constants (≥103) have become immense interest in the miniaturized memory devices that are based on the capacitive components or energy storage principles [34], [35]. It is important to study the electrical and dielectric properties from both applied and fundamental research point of view. The DC resistivity gives fundamental information about the activation energy, type of charge carriers responsible for electronic conduction and related features. To know the relaxation process occurring in a system one can study the dielectric frequency response curve. The complex electric modulus (M) study allows to distinguish the local dielectric relaxation (e.g., dipole reorientation) from long range electrical conductivity. It can also be used to determine the characteristic relaxation time. It is possible to ascribe a given process to a specific mechanism based on the values of the activation energy and the characteristic relaxation time. To the best of our knowledge, investigation on the substitution of non-magnetic ions for Ni and Zn in Ni-Zn ferrite system is not reported yet.

Therefore, an attempt has been taken to find out the effect of simultaneous change of Ni and Zn by Sn substitution in the Ni-Zn ferrite system. In this study, we have tried to produce the information about the structural, morphological, electrical and dielectric properties of pure and Sn-substituted Ni-Zn ferrites prepared by double sintering technique.

Section snippets

Materials and methods

Solid state reaction route was followed to synthesize Sn-substituted Ni-Zn ferrite, Ni0.6−x/2Zn0.4−x/2SnxFe2O4 (0.0≤x≤0.30) (NZSFO). High purity (99.5%) (US Research Nanomaterials, Inc.) oxide nanopowders was used as raw materials. The particle size of nickel oxide (NiO), zinc oxide (ZnO), iron oxide (Fe2O3) and tin oxide (SnO2) are 20–40, 15–35, 35–45 and 35–55 nm, respectively. The detail preparation technique is described elsewhere [5]. The sintering of the samples was set at 1300 °C for 4 h in

Structural properties

The X-ray diffraction (XRD) patterns of Sn-substituted Ni-Zn ferrites with the chemical composition Ni0.6−x/2Zn0.4−x/2SnxFe2O4 (NZSFO) are shown in Fig. 1. The XRD spectra were indexed and fcc cubic phase was identified as major phase. It is seen that the observed peaks (111), (220), (311), (400), (422), (511), (440) and (533) confirmed the spinel structure of the samples. The samples are single phase for x≤0.1 and thereafter (x≥0.1), the samples are identified as multi-phase in nature. The

Conclusions

The NZSFO (x=0.0, 0.05, 0.1, 0.15, 0.2 and 0.3) ferrites, sintered at 1300 °C, have been successfully synthesized and the structural, morphological and electrical properties have been studied. The lattice constant is found to be decreased, whereas enhancement of grain size is found in Sn substituted Ni-Zn ferrites. A decrease in resistivity, i.e. enhancement of conductivity and dielectrics constant, is also noticed for NZSFO (0.0≤x≤0.30). The unusual behavior of the dielectric in ferrites could

Acknowledgments

The authors are grateful to the Directorate of Research and Extension, Chittagong University of Engineering and Technology, Chittagong 4349, Bangladesh under grant number CUET/DRE/2014-15/PHY/002 for arranging the financial support for this work. We are thankful for the laboratory support of the Materials Science Division, Atomic Energy Commission, Dhaka 1000, Bangladesh.

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