Preparation of Ferrimagnetics-Ferroelectrics Composites and Studying Their Microwave Characteristics at X-Band Region

M-type barium hexaferrite (BaFe12O19) was prepared using sol-gel auto combustion method which represents substantial magnetic materials and utilized as microwave absorbers. In addition barium titanate powder was prepared using conventional ceramic method as ferroelectric material. XRD tests showed that the ferrite possess hexagonal structure and barium titanate has tetragonal structure. The constituents then mixed with different ratios and dissipated in the epoxy-resin as the sticky and fixed medium. Microwave absorbing characteristic studied within X-band region using VNA (Vector Network Analyzer). The complex permittivity and permeability were calculated using NicolsonRossWeir (NRW) method. Maximum reflection loss was -36.83dB at 9.125GHz observed for the samples A1:3 (ferrite: barium titanate) the ratio equal 1:3 due to good matching between the relative permeability and relative permittivity ,likewise the absorbing properties increases with the concentration of Barium hexaferrite in composite materials because it appeared absorption resonance frequency at 11.025 GHz.

the compound to allow the absorption of microwave energy for broadband wave attenuation [2].Chapal (2012), prepared radar absorbing materials (RAMs) by utilizing (BaTiO3-Ni0.5Zn0.5Fe2O4)magneto-electric nanoparticles, the microwave characteristics such as return loss (dB), complex permittivity and permeability were measured in the X-band region, the composite materials showed that a wider absorption frequency range and showed maximum return loss of -15.78 dB (>97% power absorption) at 10.8 GHz.Conclude the mechanism of microwave absorption occurs mainly due to the dielectric loss rather than magnetic loss [3].Vinayasree et al (2014), synthesized resilient single layer electromagnetic wave absorbers by mergers suitable amounts of carbon black (CB) in a Nitrile butadiene rubber matrix along with an optimized amount of barium Hexaferrite (BaF) for Microwave applications in S, C, and Xbands, complex permittivity and permeability were measured using the cavity perturbation method in the frequency range of 2-12 GHz.For specimen containing 30CBBaF (CB volume fraction= 0.034) minimum reflection loss reaching −47 dB at a frequency of 11 GHz for a thickness of 6 mm [4].Silvia et al (2015), prepared hard-soft nanocomposites by using sol-gel auto-composition procedure, the hard-soft Sr0.5Co0.5Nd0.5Fe10.5O19/NiFe2O4with various weight ratios were dispersed in epoxy resin then studied microwave characteristics at X-band region by using vector network analyzer (VNA), the nanocomposite with an equal amount of hard and soft phase shows higher performance both in reflectivity and in bandwidth, getting a maximum in reflectivity of -34.4 dB at 11.1 GHz while the bandwidth below -10 dB is 3.5 GHz [5].In this study microwave absorbing composites were prepared and the complex permittivity and permeability were calculated by Nicolson-Ross-Wier (NRW) method, using S-parameters data which got from the Network Analyzer.The composites consist of barium hexaferrite powder sintered at 1200℃ (known to be magneto-dielectric) and/or barium titanate powder (ferroelectrics material) dispersed in epoxy resin (as Sticky then fixed medium).the neutralized solution at 100 ℃ on a hot plate with continuous stirring until the water evaporated from the solution and become gluey, with continuing heating the compound burnt by auto-combustion process to form incoherently powder then calcined at 1200℃ for 3h.

Preparation of barium titanate
BaTiO3 was obtained via the reaction between BaCO3 and TiO2 by mixing 15.96 g of TiO2 powder with 39.456g of BaCO3 powder (molar ratio 0.2:0.2) .The mixture was milled using the conventional ceramic method, and then calcined in the furnaces at 1000℃ for 3h, then grind and calcined at 1100℃ for 3h and then at 1200℃ for 3h.Finally, we got barium titanate (BaTiO3) which showed by x-ray examinations, and then grinded to prevent conglomerates.

Preparation of composite specimens
1-The main method of preparation of samples started with mixing of One gram from (BaTiO3 or/and BaFe12O19) powders with 10g epoxy-resin (EUXIT 50) according to the table (1).
2-Ultrasonic mixer have used for half an hour for mixing the liquid mixture in order to have a good separation and a homogeneous distribution of the nanoparticles into the resin.
3-The curing agent (hardener) was added to the mixture of resin and filler through slow manual mixing for about 5 minutes.

Conclusions
Maximum reflection loss -36.83dB was observed for the samples A1:3 (ferrite:barium titanate) the ratio equal 1:3, was due to good matching the relative permeability and relative permittivity.
The complex Permeability measured for composite material which have been calculated using (NRW) method in the X-Band was larger than pure material for barium hexaferrite sintering at 1200℃ because of overlapping attenuation aggregate from ferrite and epoxy -resin this is causing the spurious values of the magnetic permeability.