Elsevier

Materials Letters

Volume 40, Issue 1, July 1999, Pages 39-45
Materials Letters

Dielectric properties of polycrystalline mixed nickel–zinc ferrites

https://doi.org/10.1016/S0167-577X(99)00046-4Get rights and content

Abstract

Dielectric properties such as dielectric constant (ε′), dielectric loss tangent (tanδ) and complex dielectric constant (ε″) has been investigated in the frequency range 100 kHz–1 MHz. The variation of these parameters with composition, frequency and temperature is explained qualitatively. The dielectric constant for these ferrites is approximately inversely proportional to the square root of the resistivity. An attempt is made to explain the possible mechanism.

Introduction

The polycrystalline ferrites, which have many applications at microwave frequencies are very good dielectric materials. The dielectric properties of ferrites are dependent on several factors including the method of preparation, sintering temperature, sintering time and chemical composition. Ferrites have a very low conductivity, which is also one of the considerations for microwave application. With a view to the understanding of dielectric phenomena in mixed nickel–zinc ferrites, a systematic study of dielectric properties as a function of composition, frequency and temperature was undertaken; the results of the study are presented in this paper.

Section snippets

Experimental details

The ferrite samples used in the present investigation having the compositional formula NixZn1−xFe2O4, where x ranges from 0.2 to 1.0 and were synthesized by using a standard double sintering ceramic technique. The final sintering was done at 1200°C for 6 h, with subsequent slow cooling to room temperature. The details of method of the preparation have been given in an earlier publication [1]. The dielectric properties of mixed Ni–Zn ferrites were measured in the frequency range 100 kHz to 1 MHz

Dependence of dielectric properties on composition

The room temperature values of dielectric constant (ε′), the dielectric loss tangent (tanδ) and the complex dielectric constant (ε′) for mixed Ni–Zn ferrites at 100 kHz are given in Table 1. The values of electrical conductivity (σ) are measured at room temperature by two probe method and Fe2+ concentration has been estimated by titration method are also included in the table to facilitate the discussion. An examination of Table 1 reveals that the values of ε′, tanδ and ε″ are found to decrease

Acknowledgements

One of the authors (DR) is grateful to University Grants Commission, New Delhi for the award of U.G.C. Career Award in Physics. Authors are also thank Prof. K.S.N. Murthy, Head, Department of Physics for his constant encouragement.

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