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1 2004

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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.