Preparation and radar-absorbing properties of Al 2 O 3 /TiO 2 /Fe 2 O 3 /Yb 2 O 3 composite powder

Al 2 O 3 /TiO 2 /Fe 2 O 3 /Yb 2 O 3 composite powder was synthesized via the sol–gel method. The structure, morphology, and radar-absorption properties of the composite powder were characterized by transmission electron microscopy, X-ray diffraction analysis and RF impedance analysis. The results show that two types of particles exist in the composite powder. One is irregular flakes (100–200 nm) and the other is spherical Al 2 O 3 particles (smaller than 80 nm). Electromagnetic wave attenuation is mostly achieved by dielectric loss. The maximum value of the dissipation factor reaches 0.76 (at 15.68 GHz) in the frequency range of 2–18 GHz. The electromagnetic absorption of waves covers 2–18 GHz with the matching thicknesses of 1.5–4.5 mm. The absorption peak shifts to the lower-frequency area with increasing matching thickness. The effective absorption band covers the frequency range of 2.16–9.76 GHz, and the maximum absorption peak reaches −20.18 dB with a matching thickness of 3.5 mm at a frequency of 3.52 GHz.