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Synthesis and characterization of nanocrystalline Ba3Co0.9Cu1.1Fe24O41 powder and its application in the reduction of radar cross-section

Da Rocha Caffarena V., Ogasawara T., Pinho M. S., Leixas Capitaneo J. L.

Materials Science Poland

2007

Vol. 25, No. 3

875--884

There has been a growing and widespread interest in the development of radar absorbing materials (RAM). Z-type hexaferrite is one of the most complex compounds in the family of hexaferrites that may be used in many applications. In this work, the citrate sol-gel process under an inert atmosphere was used to obtain the nanocrystalline Ba3Co0.9Cu1.1Fe24O41 powder to be used as RAM. Cu2+ ions were incorporated into the structure of Ba3Co2Fe24O41 and, consequently, low temperature sintering and good magnetic properties were achieved. Composites of Ba3Co2Fe24O41 with polychloroprene (CR) were obtained for microwave absorption measurements by the transmission/reflection method, using a waveguide medium for the S- band and X-Ku bands. The 80:20 nanocomposite of Ba3Co0.9Cu1.1Fe24O41:CR with 3.0 mm thickness exhibited the best performance as a RAM for the X-band, with 99.50% microwave absorption at 9.5 GHz.

Effect of double substituted m-barium hexaferrites on microwave absorption properties

Lima R. C., Pinho M. S., Gregori M. L., Nunes R. C., Ogasawara T.

Materials Science Poland

2004

Vol. 22, No. 3

245--252

The complex permeability ( a?r*) and permittivity ( e?r*) of radar absorbing materials (RAMs) play a key role in determining the reflection and attenuation properties of incident microwaves. Their real (a?' and e?') and imaginary (a?'' and e?'') components and relationship with microwave absorbing properties have been investigated in the frequency range 8-16 GHz for doped M-type barium hexaferrites in polychloroprene (CR) matrices. Individual and simultaneous substitutions of Fe3+ ions by Co2+, Ti4+, and Mn3+, and of Ba2+ ions by La3+ and Na+ make possible the use of these materials as RAMs, due to frequency dependence of ??* of hexaferrite, responsible for the location of its natural resonance. A double substitution of Ba2+ and Fe3+ (LaNaCoTiMn-BaHF) resulted in the best microwave absorption (99.9%) at the frequency of 15 GHz.