M-type ferrite composite as a microwave absorber with wide bandwidth in the GHz range

The electromagnetic wave absorption properties of Ba M-type (BaFe12-x(Ti0.5 Mn0.5)(x)O-19) ferrite - epoxy resin composites were investigated. After me asuring the complex permittivities of the samples, the regions of complex p ermeabilities in which the reflection loss (R.L.) becomes less than -20 dB (-20 dB Regions), were calculated. Altering the conditions such as sinterin g temperature, particle size and the ratio of ferrite powder in the composi te samples, resulted in frequency dependencies of permeabilities that agree well with the calculated -20 dB regions, and which lead to an expansion in bandwidth (frequency range (Delta f) of R.L. < -20 dB). The BaFe9(Ti0.5Mn0 .5)(3)O-19 ferrite-resin composite, which was produced by sintering at 1573 K for 20 h, crushing into powder (150-300 mu m) and mixing with epoxy resin at a ratio of 70 mass%, exhibited a wide bandwidth (Delta f=7.2 GHz) from 13.75 GHz to 20.95 GHz. Delta f values of 1.4-5.4 GHz in the frequency rang e 6.35-15.65 GHz, were obtained by changing the composition of the BaFe12-x (Ti0.5Mn0.5)(x)O-19 / epoxy resin composite from x=3.5 to 4.5.