2004 Volume 45 Issue 8 Pages 2606-2609
In this paper, the electromagnetic wave absorption properties of Co-Ti substituted Ba M-type hexagonal ferrite (BaFe9.5(Co1−yTiy)2.5O19 (y = 0.4 ∼ 0.8)) produced by a modified coprecipitation method were investigated. This modified chemical coprecipitation method was the combination of the coprecipitation and the synthesis from a salt melt. The sample, Ba9.5(Co0.5Ti0.5)2.5O19 sintered at 1423 K for 5 h, whose powder was produced by the modified coprecipitation method, exhibited high permeability (μr″ max = 11) and reflection loss (R.L.) around −10 dB at a relatively wide frequency range (0.8 ∼ 9 GHz) comparable to the Ultra Wide Band (UWB). In order to enhance the sintering, the addition of Bi2O3 was carried out. The Ba9.5(Co0.4Ti0.6)2.5O19 sample sintered at 1423 K for 5 h with a Bi2O3 content of 2 mass%, exhibited high permeability (μ″r max = 25 and μ″r at 1 GHz = 10). This sample also showed good microwave absorption properties (reflection loss: R.L. < −20 dB) with a small matching thickness (dm) of 3.1 mm at 0.65 GHz and f · d product (f · d) of 2.0 GHz·mm. It can be said that the Ba M-type ferrite produced by the modified coprecipitation method has a possibility to become a material for the thinner microwave absorber in the several GHz range.
