Development of “tuned microwave absorbers” using U-type hexaferrite

• Published in: Materials in engineering 2010-08, Vol.31 (7), p.3220-3226
• Main Authors: Meena, R.S., Bhattachrya, Sudeshna, Chatterjee, Ratnamala
• Format: Article
• Language: English
• Subjects: Complex permittivity; Electromagnetic interference; Electromagnetic properties; Frequency ranges; Microwave absorbers; Microwave absorption; Microwave absorption (E); Microwaves; Tuned microwave absorber (H); U-type hexaferrite (A); X-band
• ISSN: 0261-3069
• DOI: 10.1016/j.matdes.2010.02.019

The paper presents that microwave absorption is tunable with sample thickness over a frequency range if electromagnetic properties of the sample do not change with frequency in that range. The work summarizes the results of polycrystalline samples of two U-type hexaferrite series: Ba 4 (Co 1−5 x P 2 x ) 2 Fe 36 O 60 (0.0 ⩽ x ⩽ 0.20 in step 0.05) and (Ba 1−3 x La 2 x ) 4 Co 2 Fe 36 O 60 (0.10 ⩽ x ⩽ 0.25 in step 0.05) that have been prepared through solid state reaction route. The complex permittivity, permeability and microwave absorbing properties have been discussed in detail for X-band (8.2–12.4 GHz) frequencies. The results show that the substitution of Co 2+ ion with P 5+ ion and Ba 2+ ion with La 3+ ion in the U-type-hexaferrite provides the desired electromagnetic properties for a “tuned microwave absorber” in samples with x = 0.05 and 0.20 of first and 0.20 sample of second series. In these samples, the microwave absorption peak (of >98%) shifts linearly from lower to upper side of X-band with sample thickness. These materials can provide significant application for reduction of radar cross section (RCS) and in electromagnetic interference (EMI) shielding.