Dielectric properties of polycrystalline mixed nickel–zinc ferrites
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.
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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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