Fabrication and Microwave Absoption Properties of Hexaferrite Composites in Ku-band Sukhleen Bindra Narang*, Guntaas Kaur, Deepank Aggarwal, Kunal Pubby, Pawandeep Kaur Department of Electronics Technology, Guru Nanak Dev University, Amritsar, Punjab, India Abstract- In this research, M-type hexaferrites doped with Co,Ti, Sr(CoTi)xFe(l2_2xPI9 (x=O.O, 0.2, 0.4, 0.8, 1.0) have been synthesized using normal ceramic technique. Properties like complex permittivity, complex permeability and relection loss of composites of these hexaferrites with epoxy resin have been measured in Ku-band i.e. 12.4-18 GHz. I. INTRODUCTION Hexagonal ferrite composites play a major role in applications related to telecom, high speed electronics, electromagnetic wave attenuation and interference suppression [1-5]. These materials are now preferred over traditional ferrites due to high saturation magnetization, high coercivity, high ferromagnetic resonance requencies (FMR) and low cost. Their hard magnetic properties originate rom their comparatively high crystalline anisotropy in which the high anisotropy ield is along the c-axis of the crystal [6]. Strontium hexaferrite is a ferri-magnetic material, with a hexagonal structure belonging to the space group of P63/mmc. Its crystal structure is built of alternate basic blocks S and R. The S block contains two oxygen layers forming a spinel structure and R block is a three-oxygen layer block, with a hexagonal structure, containing the strontium ion. The 24 Fe3+ atoms are distributed over ive sub-lattice sites: three octahedral sites (I2k, 2a and 42), one tetrahedral site (4fl) and one bi pyramidal site (2b). The Fe3+ ions with up-spin are distributed on the 2a, 12k and 2b sites and ions with downspin are located on the 4fl and 42 sites [7]. The magnetic and microwave absorption properties can be enhanced by the substitution of Zn 2 +, C0 2 +, Zr4+, Sn 2 +or rare earth elements such as Pr3+ La3+ H03+etc [2-5] in the place of Fe3+ ions. Continuing tha� chai� of research, Sr- hexaferrites doped with C0 2 + and Ti4+ ions have been prepared in this research. II. EXPERIMENTAL The series of strontium hexaferrite doped with cobalt and titanate ions with the composition of Sr(CoTi)xFe(1 2 _ 2 xpI9 (x=O.O, 0.2, OA, 0.8, 1.0) have been synthesized using a normal ceramic combustion method. The stoichiometric mixtures of SrC0 3 , CoC0 3 , Ti0 2 , Fe 2 0 3 with 99.9% purity have been crushed and mixed in a ball mill thoroughly for 6 hours in acetone. This mixture has been dried and fed for calcination to evolve the residual gases at 1000°C for 12h in air. The calcined powder has been crushed thoroughly using pestle mortar to get equally distributed grain size. The ferrite epoxy composites have been made by granulating the grounded powder (70% of total mixture) and adding epoxy (30%) as a binder. The mixtures have cured with diethylenetriamine hardener by adding 1-2 drops of it. The ferrite epoxy mixture has been fed on Ku-band rectangular wavelength sized aluminum sheet (I5.7988mm x 7.8994mm) and has been kept for drying in isolation for 72h at room temperature. The dried ferrite composites of thickness 2 mm have been taken off rom the AI sheets. Nicolson Ross method in N5225A modeled Programmable Network Analyzer of Agilent Technologies has been used to ind scattering parameters, complex pennittivity, complex permeability with respect to requency [8]. II. RESULTS AND DISCUSSION A. Complex permittiviy and permeabiliy Hexaferrites are the potential candidates for magneto dielectric applications in microwaves since it exhibit signiicant permittivity and permeability at these requencies and the M-type hexaferrites exhibit ferromagnetic resonance in GHz range. Complex permittivity and complex permeability collectively goven the lossy characteristics of a material when an electromagnetic wave passes through it. Fig. 1 and ig. 2 show the real and imaginary part of permittivity for all the composite samples respectively. It is observed that imaginary part of pennittivity for the samples x=O.O and 0.2, is nearly zero and some variations are shown for x=OA, 0.8 and 1.0 across the value zero showing some dielectric loss. Similarly, the real part of permittivity shows insigniicant changes for x=O.O and 0.2. The complex pennittivity of hexaferrites is mainly due to the electronic polarization, ionic polarization, intrinsic polarization and interfacial polarization [2, 9]. The positive ions of Sr+ 2 and Fe+3 surrounded by 0- 2 ions contribute to dielectric constant (E') and dielectric loss (E") through dipolar polarization and dipole relaxation res ectivel .. .. -w 0"" : .£ " - ..- ' - ' , .- ) = � 5 . 10 8 6 4 2 0 -x=O.O -x=O.2 -x=OA 12 14 16 18 Frequency(Gz) Fig. 1: Real part of permittivity for all samples The peaks are present due to the phenomenon of ferromagnetic resonance (FMR). Fig. 3 and ig. 4 show the real and imaginary part of permeability respectively. 978-1-4673-9536-6/15/$31.00 ©2015 IEEE