1784 Research Article International Journal of Current Engineering and Technology ISSN 2277 - 4106 © 2013 INPRESSCO. All Rights Reserved. Available at http://inpressco.com/category/ijcet Magneto-Dielectric and Electromagnetic Absorbing studies of Antimony Doped Nickel Ferrites Erum Pervaiz Ȧ and I.H.Gul Ȧ* Ȧ Thermal Transport Laboratory (TTL), School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), H-12 Islamabad., PAKISTAN Accepted 05 November 2013, Available online 01 December 2013, Vol.3, No.5 (December 2013) Abstract Antimony (Sb 3+ ) doped nickel ferrites (NiSb x Fe 2-x O 4 ) with x=0.0, 0.035, 0.065 and 0.1, have been synthesized by hydrothermal route using an autoclave at 160 0 C for 12 hrs. AC conductivities for all the samples have been observed in the frequency range of 1MHz to 3 GHz, where AC conductivity increases due to the addition of antimony in nanocrystalline nickel ferrites. Electromagnetic properties were studied by measuring complex dielectric permittivity (ɛ*), complex magnetic permeability (μ*) in the frequency range of 1 MHz to 3 GHz at room temperature using RF/impedance analyzer. Reflection losses (RL) were calculated for all the samples using permittivity and permeability measurements according to the transmission line theory. Maximum RL of -54dB was obtained for antimony doped nickel ferrite x=0.065 at 2.4 GHz with a band width of 1.2 GHz and decreases for high antimony concentration x=0.1 (-49dB). Low dielectric permittivity, high permeability and conductivity made this material a compatible option for single layered and multilayered chip inductors. While low RL values suggest nickel ferrite a possible candidate for electromagnetic absorption devices and radar absorbing material. Keywords: Antimony nano ferrite, Complex dielectric permittivity, Complex permeability, Reflection losses. 1. Introduction 1 Ferrites (spinel and hexagonal) have been considered as promising ceramic materials for the use in high frequency applications due to the inherent insulating and dielectric characteristics and capacity of absorbing electromagnetic waves to enhance electromagnetic interference suppression (EMIS) (V. G. Harris et al., 2009, R. Valenzuela et al., 2012). Spinel ferrite nanoparticles have been investigated since many years as good microwave absorbing materials due to their low dielectric and magnetic losses. In the class of spinel ferrites nickel nano ferrite and its derivatives like Ni-Zn (X. Feng et al., 2007), Ni-Al (I. H. Gul et al., 2012), Ni-Cu-Zn (S. Y. Tong et al., 2013) and Ni-Re (E. E. Sileo et al., 2004) have been under consideration mostly due to high DC-electrical resistivity and low density, low permittivity losses and flexibility. Nickel ferrite in pure and in the form of composite with polymers are preferred as electromagnetic (EM) absorbing materials in high frequencies (HF) and ultra high frequencies (UHF) [S. M. abbas et al., 2007). Physical properties of all the class of spinel ferrites are largely based upon type and concentration of substituting cations, the way they occupy the crystal lattice, synthesis route, sintering temperature and sintering time (E. Pervaiz et al., *Corresponding author’ Tel: 0092-51-90855206 2013). Synthesis route, sintering behavior and cation substitution all thesis parameters directly influence the microstructure of prepared ferrites that define the properties and behaviors of prepared spinel ferrites (A. M. M. farea et al., 2008). Nickel ferrite is an inverse ferrimagnetic spinel ferrite with Ni 2+ ions occupied at octahedral sub-lattices (B-sites) and Fe 3+ ions occupied at tetrahedral (A-sites) and octahedral sub-lattices equally (K. S. Muthu et al., 2013). Doping of nickel ferrites with different divalent and trivalent cations imparts distinct electrical and magnetic properties characterized by shift of ions between two sub-lattices. Many researches are available on the synthesis and EM absorbing properties of nickel ferrites and its composites with different materials (Z. H. Yang et al., 2012, D. L. Zhao et al., 2009, Y. Yang et al., 2012). In all the studies two things are normally required for a material to become good EM/Microwave absorber. One is the matching thickness of the absorbing layer and second is the mechanical, thermal and chemical stability for the military use and stealth technologies (Y. J. Shin et al., 1993). Hexa-ferrites used for EM/microwave absorbing applications need thick absorbers to obtain a significant absorption of incident electromagnetic waves, while spinel ferrites with low thickness (~ 2mm) could possibly serve the purpose alone or with insulating polymers. (B. F. Zhao et al., 2013) have studied the microwave absorbing properties of LiZnFe 2 O 4 . (Ch.