Study the Microwave absorption characteristics of U-type barium hexaferrites prepared using chemical method


U-type Barium hexaferrite with stoichiometric composition Ba4Co0.3Zn0.6Cu1.1Fe36O60 has been prepared using citrate precursor method at low temperatures (1000, 1050, and 1100°C). The XRD patterns of the prepared powders at temperatures (1000 and 1050°C) show the presence of spinel, M and Y-type phases, while U-type ferrite phase(with crystallite size 40 – 90 nm) obtained at 1100 °C. Radar absorbing nanocomposite samples were prepared by mixing, molding and curing mixtures of Ba4Co0.3Zn0.6Cu1.1Fe36O60 powders (prepared at 1100°C) with epoxy resin (ER),(80:20% weights).The microwave attenuation measurements were based on the Transmission/Reflection method using rectangular waveguides as the confining medium for the samples at 8.0–12 GHz frequencies.
The complex dielectric constant, complex permeability ( εr′, εr″,.r' and r" ) and losses(tan δ and tan δμ ) of hexaferrite-epoxy resin composites were measured in the range of 8 -12 GHz. Measured results show that the parameters εr′, εr″,.r' , r" tan δ and tan δμ exhibited very small change as the measuring frequency increasing at (9.2–11.2 GHz). The results also indicate that the content of copper and zinc ions closely affects the microwave properties of composite samples, resulting in microwave absorption greater than 90.0 % (reflectivity ≤ -10 dB) at 9.2-11.2 GHz with 2.0 mm thickness. Attenuation matching results show that the electromagnetic wave propagation in ferrite is slower than that in free space by six times, this result may help us to design microwave absorber at x-band frequencies with 2 mm thickness.
Keywords: RAM ,U-type ferrite, XRD, x-band, microwave properties, hexaferrites, and reflection loss.