Hexagonal Ferrite Electromagnetic Wave Absorption Characteristics

In this paper, the electromagnetic and absorption properties of polycrystalline hexagonal femtes,Ba(TixCox)Fei2-2xOi9(M-type), Ba(Zni.xCox)2Fei6O27(W-type) and Ba3(Zni.xCox)2Fe24O4i(Z-type) have been investigated. The samples were prepared by the usual ceramic sintering, and the parameters such as complex permeability , complex permittivity f , reflection loss R(dB) were tested. Meanwhile, the temperature stability was studied, and some good results were obtained.It was proved that ,2 firstly increased then decreased in the range from 1 MHz to1.8 GHz with increasing Co2"1" substitution, and higher values of | | of Z-type materialwere obtained in comparison with M-type and W-type hexaferrite, = 25, whichexceed the reported value of congener material currently. The minimum fr was achieved when x=l.l(M-type),x=0.35(W-type) and x=0.4(Z-type). In the case of Ba3(Zno.6Coo.4)2Fe24O4i, // decreased and fr increased when Ba2+ was substituted by Sr2+,Co2+ was substituted by Cu2+, and Zn2+ was substituted by Mn2+.Dielectric properties of hexaferrite were restricted by Fe2+, s of Ba(TixCox)Fei2-2X -Oi9 increased with increasing Co2"1" substitution , the highest values of sr\ of Ba(Zno.35 -Coo.esVyF^Os (W-type)and Ba(Zno.6Coo.4)2'nFe203 (Z-type) were obtained when y=8 andn=11.7.The curves of , and R(dB) of Z-type hexaferrite varietied faintly when temperature changed in the range of 15~175C,and 15~ 125C,which were prior to M-type and W-type hexaferrite.According to results of the calculated reflection loss(dB),the absorption peak shifted to a lower frequency with increasing the thickness ,and shifted to a higher frequency with increasing the angle of oblique incidence. Meanwhile, R(dB) variety delicately as 6 <30?. The tested curve of R(dB) of Z-type composite coincided with the calculated R(dB), which means that the calculated reflection loss(dB) was right. In the range of 200~800MHz,the R(dB) of sintered Z-type hexaferrite was above IdB lower than M-type and W-type hexaferrite with the same thickness of 3mm, which provides a new approach to improve the absorption properties in the range. This material has a bright application future in the civilian and military field.