Elsevier

Applied Surface Science

Volume 258, Issue 14, 1 May 2012, Pages 5342-5347
Applied Surface Science

Low dielectric loss of Mg doped Ni–Cu–Zn nano-ferrites for power applications

https://doi.org/10.1016/j.apsusc.2012.01.158Get rights and content

Abstract

Magnesium substituted nickel copper zinc nano-ferrite having the general formulae Ni0.5−xCu0.2Zn0.3MgxFe2O4 (0.0  x  0.4) were prepared at relatively lower temperature (900 °C) by sol–gel technique. Thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy were used for the characterization of as-synthesized samples. It has been observed that the value of permittivity increases to a maximum value of ∼8 × 102 for x = 0.4 sample. A remarkable decrease in power loss and loss tangent has been observed with the increase in Mg concentration. The Cole–Cole diagrams were investigated in which a single semi-circle is obtained for all the samples except for the sample with x = 0.4. The presence of two semi-circles for the sample with x = 0.4 indicates that the conduction is due to the grain and grain boundary, while for the rest of the samples the conduction due to the grain boundary is predominant. An improvement in magnetic properties has also observed in the magnesium substituted nickel copper zinc nano-ferrite. Also coercivity was found to decrease with Mg concentration which is useful for power applications.

Highlights

► Magnesium substituted Nickel Copper Zinc nano-ferrite having general formulae Ni0.5−xCu0.2Zn0.3MgxFe2O4(0.0  x  0.4) has been prepared at relatively lower temperature (900 °C) by sol-gel technique. The value of permittivity is observed to increase to a maximum value of ∼8 × 102 for x = 0.4 sample. A remarkable decrease in power loss and loss tangent is observed with the increase in Mg concentration, which is useful for power application of ferrites. Improvement in magnetic properties has also been observed in the magnesium substituted Nickel Copper Zinc nano-ferrite.

Introduction

Magnetic nano-materials have received considerable attention because of their unique magnetic properties. Ni–Cu–Zn ferrites are well established soft magnetic material for Multilayer inductor chip (MLIC) applications because of their relatively low sintering temperature, high permeability in the radiofrequency (RF) region and high electrical resistivity [1], [2]. The electronic component with small size, high efficiency, and low cost are the basic requirement for their applications. Multilayer inductor chips (MLIC) is an important component, widely being used in electronic products, such as cellular phone, notebook computer, and video cameras [3]. Ni–Cu–Zn ferrites have been the dominant materials for MLIC due to its better magnetic properties at high frequency and low sintering temperature [4], [5]. On the other hand, Ni–Cu–Zn ferrites have some disadvantages with respect to multi-layer fabrication and device performance. Nickel and its oxide are classified as environmentally hazardous and a carcinogen [6]. Moreover, serious compatibility problems between Ni–Cu–Zn ferrites and fine-line-printed Ag coil turns pose limitations on the performance. Mg–Cu–Zn ferrite has been considered as an alternative system to overcome these difficulties, owing to its high resistivity, high Curie temperature, and environmental stability [7]. The magnetostriction constant of Mg–Cu–Zn ferrite is also lower than that of Ni–Cu–Zn ferrite; MLIC using Mg–Cu–Zn ferrite would provide better magnetic properties. Mg-containing composition is also preferred in order to obtain highly dense and resistive ferrites [8], [9]. It is then expected that Mg addition in Ni–Cu–Zn ferrites may improve the dielectric and magnetic properties. Several methods have been used for the synthesis of Ni–Cu–Zn ferrites like conventional ceramic [10], [11], sol–gel [12], [13], egg-white, chemical co-precipitation [14], [15] etc., out of these methods sol–gel process has advantages of being able to use inexpensive precursors, a simple preparation method and low sintering temperature that results in well dispersed homogenous, nano-sized and highly reactive ferrite powder. Few studies on the electro-magnetic properties of Mg doped Ni–Cu–Zn ferrites are reported in the literature. Recently Roy and Bera [16] have used nitrate–citrate auto-combustion method for Ni0.25−xMgxCu0.2Zn0.55Fe2O4 ferrite synthesis. Gabal [17] has studied the electro-magnetic properties of Ni0.5−xCu0.2Zn0.3MgxFe2O4 synthesized by egg-white method.

In the present study we have reported the synthesis of Ni0.5−xCu0.2Zn0.3MgxFe2O4 (0.0  x  0.4) nano-ferrite by sol–gel method using ethylene glycol. The influence of Mg on the dielectric, impedance and magnetic properties of Ni0.5−xCu0.2Zn0.3MgxFe2O4 (0.0  x  0.4) ferrite samples were also investigated. These nano-ferrite samples exhibited an increase in permittivity, remarkable decrease in dielectric losses and a decrease in coercivity with increase in magnesium concentration in Ni–Cu–Zn ferrite.

Section snippets

Synthesis

Nano-crystals of Ni0.5−xCu0.2Zn0.3MgxFe2O4 (0.0  x  0.4) ferrites were synthesized using analytical grade Fe(NO3)3·9H2O, Zn(NO3)2·4H2O, Cu(NO3)2·4H2O, Mg(NO3)2·4H2O. Stoichiometric amounts of metal nitrates were dissolved together in minimum amount of double distilled water and ethylene glycol was added to the resulting solution in 1:1 ratio under constant stirring. Using a magnetic stirrer and keeping the temperature at 70 °C the solution was constantly stirred until the gel formation. The gel so

Results and discussion

Typical thermo gravimetric analysis (TGA) curves of the Ni0.5−xCu0.2Zn0.3MgxFe2O4 (0.0  x  0.4) dried gel from room temperature to 800 °C are shown in Fig. 1. The TGA curves exhibit three distinct weight loss steps. The curves show that, decomposition rapidly propagated forward until all the gel was completely burnt out at about 410 °C. The first weight loss step is observed around 100 °C which is attributed to the loss of water entrapped in the dried gel. The second weight loss step is from 340 °C

Conclusions

XRD results indicate that the pure phase magnesium substituted Ni–Cu–Zn ferrite was synthesized at relatively lower temperature (900 °C) by sol–gel technique. A decrease in the power loss and ac conductivity has been found on Mg substitution, which is useful for power application of ferrites. It is also observed that the value of permittivity increases up to ∼8 × 102 for composition with x = 0.4. Cole–Cole plots are observed to show a single semi-circle for all the samples, except for the sample

Acknowledgements

The authors are grateful to Director, National Physical Laboratory; New Delhi for providing constant encouragement and motivation to carry out this work. One of the authors (M. Abdullah Dar) is also thankful to U.G.C. for their financial assistance.

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