Electromagnetic and Microwave Absorption in Y-Type Ba2Co2₋xZnxFe12O22 Hexaferrites

Abstract

Y-type hexaferrites with the nominal composition Ba2Co2₋xZnxFe12O22 (x = 0 and 1) were made using the standard solid state reaction procedure and sintered at 1000 °C. The structure of the sample in X-ray diffraction showed a single phase of Y-type with a high crystallinity and minor increase in lattice parameters owing to the replacement of Zn2+ ions by Co2+. The crystallite size decreased slightly due to the presence of Zn ions, which must have inhibited the growth of the grain and enhanced the microstructural homogeneity. X-band (8-12 GHz) measurements with a vector network analyzer showed that incorporation of Zn increased both dielectric and magnetic losses by a considerable amount giving improved impedance matching and increased absorption efficiency. Best reflections loss was recorded to be 37.8 dB at 10.4 GHz at an effective absorption bandwidth of over 2.3 GHz with a composition of Ba2Co2₋xZnxFe12O22, as compared to Ba2Co2Fe12O22 which has a reflection loss of 28.6 dB at 9.7 GHz. The increase in absorption is explained by the synergistic processes in terms of dipolar polarization, domain wall resonance and balanced dielectric-magnetic coupling. These observations point to the conclusion that Zn-modified Y-type hexaferrites are the good candidates to be used in radar absorbing coating, electromagnetic shielding, and microwave-photonics.