Microwave absorption properties of Ba M-type ferrite prepared by a modified coprecipitation method

The electromagnetic wave absorption properties were investigated in the Co-Ti substituted Ba M-type hexagonal ferrites (BaFe9.5(Co1-yTiy)(2.5)O-19 (y = 0.4-0.8)), which were prepared by a modified coprecipitation method. This modified chemical coprecipitation method was the combination of coprecipitation and synthesis from a salt melt. The Ba-9.5(Co0.4Ti0.6)(2.5)O-19 sample, which was sintered at 1423 K for 5 h with a Bi2O3 addition of 2 wt%, exhibited high permeability (mu(r)''(max) = 25 and mu(r)'' at 1 Ghz = 10). This sample also showed a good microwave absorption property (reflection loss: RL < -20 dB) with a small matching thickness (d(m)) of 3.1 mm at 0.65 GHz. It is concluded that the Ba M-type ferrite prepared by the modified coprecipitation method has a possibility to become a candidate for thinner microwave absorbers in the gigahertz range. (c) 2004 Elsevier B.V. All rights reserved.