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

The electromagnetic wave absorption properties of Ba M-type (BaFe _12-x(Ti_0.5Mn_0.5)_xO₁₉ ) ferrite-epoxy resin composites were investigated. After measuring the complex permittivities of the samples, the regions of complex permeabilities in which the reflection loss (R.L.) becomes less than -20 dB (-20 dB Regions), were calculated. Altering the conditions such as sintering temperature, particle size and the ratio of ferrite powder in the composite 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 (Δf) of R.L. <-20 dB). The BaFe₉(Ti_0.5Mn_0.5) ₃O₁₉ ferrite-resin composite, which was produced by sintering at 1573 K for 20 h, crushing into powder (150-300 μm) and mixing with epoxy resin at a ratio of 70 mass%, exhibited a wide bandwidth (Δf=7.2 GHz) from 13.75 GHz to 20.95 GHz. Δf values of 1.4-5.4 GHz in the frequency range 6.35-15.65 GHz, were obtained by changing the composition of the BaFe_12-x(Ti_0.5Mn_0.5)_xO ₁₉/epoxy resin composite from x=3.5 to 4.5