Enhancement of microwave absorption of nanocomposite BaFe12O19/α-Fe microfibers

Nanocomposite BaFe12O19/α-Fe microfibers with diameters of about 1–5 μm are prepared by the organic gel-thermal selective reduction process. The binary phase of BaFe12O19 and α-Fe is formed after reduction of the precursor BaFe12O19/α-Fe2O3 microfibers at 350 °C for 1 h. These nanocomposite microfibers are fabricated from α-Fe (16–22 nm in diameter) and BaFe12O19 particles (36–42 nm in diameter) and basically exhibit a single-phase-like magnetization behavior, with a high saturation magnetization and coercive force arising from the exchange-coupling interactions of soft α-Fe and hard BaFe12O19. The microwave absorption characteristics in a 2–18 GHz frequency range of the nanocomposite BaFe12O19/α-Fe microfibers are mainly influenced by their mass ratio of α-Fe/BaFe12O19 and specimen thickness. It is found that the nanocomposite BaFe12O19/α-Fe microfibers with a mass ratio of 1:6 and specimen thickness of 2.5 mm show an optimal reflection loss (RL) of −29.7 dB at 13.5 GHz and the bandwidth with RL exceeding −10 dB covers the whole Ku-band (12.4–18.0 GHz). This enhancement of microwave absorption can be attributed to the heterostructure of soft, nano, conducting α-Fe particles embedded in hard, nano, semiconducting barium ferrite, which improves the dipolar polarization, interfacial polarization, exchange-coupling interaction, and anisotropic energy in the nanocomposite BaFe12O19/α-Fe microfibers. (interdisciplinary physics and related areas of science and technology)