TEZUKA Nobuki Graduate School of Engng., Res. Assoc., 大学院・工学研究科, 助手 (40323076)
KAGOTANI Toshio Graduate School of Engng., Res. Assoc., 大学院・工学研究科, 助手 (40005343)
INOMATA Koichiro Graduate School of Engng., Prof., 大学院・工学研究科, 教授 (90323071)
OTA Hiroyasu Telecommunications Advancement Organization of Japan, Sendai EMC-RC, Groop Leader, 仙台EMC?RC, 主任研究員
|Budget Amount *help
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 2002: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 2001: ¥4,700,000 (Direct Cost: ¥4,700,000)
[Purpose] In this study, sintered bodies composed of a mixture of M and W-type phases were prepared and their electromagnetic wave absorption properties were investigated. As its magnetic properties are similar to those of M-type ferrite, Zn added BaW-type ferrite (BaZn_2-W) was chosen for this work.
[Experimental] The sintered body samples had composition of BaZn_<2x>Fe_<12-x+4y> (Sn_0.5>Mn_<0.5>)x O_<19+8y> (1.2≦x≦2.0, 0.25≦y≦0.75), and were sintered at temperatures between 1473 K and 1573 K. The phases present were analyzed by X-ray diffraction (XRD), and were shown to consist of BaM and BaZn2W-type hexaferrite phases. The relative complex permeability (μr′and μr″) and permittivity (εr′and εr″) of toroibally shaped sintered samples were calculated from S-parameter values measured using a Hewlett-Packard HP8720D network analyzer, in the frequency range 0.O5〜20.O5GHz.
[Results] In all samples sinlered at 1473K〜1573K with x=1.2 and y=0.5, two peaks, corresponding to the M and W-type phases, were observed in the frequency dispersion of the relative complex permeability. In the T=1473K and 1523K samples, which showe Reflection Losses (R.L.) less than -2OdB, ΔF was 2.2 and 0.7GHz, respectively. Therefore, a sintering temperature of T=1473K was selected, and the compositional ratio of M and W phases (y) was varied between 0.25 and 0.75. Almost the same matching thickness (dm) was obtained for all of the samples, however the y=0.5 sample exhibited the largest ΔF value. Therefore, in the BaZnFe10.8(Sn0.5Mn0.5)1.2O23 sample sintered at 1473K, ΔF was wider (2.2GHz) than for a M-type single phase sintered body, with a relatively small matching thickness of dm=1.Omm. It is concluded that using a two-phase microstructure composed of M and W-type hexaferrite, is an effective method of expanding ΔF.