Abstract: A soft hexagonal ferrite sintered material includes crystal particles of M-type hexagonal ferrite corresponding to a general chemical formula MFe12O19 wherein M is at least one element selected from the group consisting of Ba, Sr and Pb. Crystal particles having particle diameters of 5 ?m to 100 ?m are extracted from a sintered material produced from a precursor powder mixture. The extracted particles as seed crystals are mixed with a calcined powder comprising fine crystals having the above composition and particle diameters of 0.5 ?m to 3 ?m, then is sintered until the intended particle growth of the crystal particles in the sintered material is achieved to give an average particle diameter of 30 ?m to 500 ?m.

Abstract: A radio wave absorber is provided which can be produced at a low cost compared to the case of using silicon carbide fiber and which is also superior in radio wave absorption property in 76 GHz band (75-77 GHz frequency band). The radio wave absorber is produced by arranging a radio wave absorbing layer onto the surface of a metal body. The radio wave absorbing layer is made of a radio wave absorbing material containing silicon carbide powder dispersed in matrix resin. Average particle diameter of the silicon carbide powder is 4-40 ?m. Silicon carbide powder content in the radio wave absorbing material is 15-45 volume %. Thickness of the radio wave absorbing layer is adjusted so that reflection attenuation of not less than 10 dB is provided in 76 GHz band.

Abstract: A radio wave absorber is provided which can be produced at a low cost compared to the case of using silicon carbide fiber and which is also superior in radio wave absorption property in 76 GHz band (75-77 GHz frequency band). The radio wave absorber is produced by arranging a radio wave absorbing layer onto the surface of a metal body. The radio wave absorbing layer is made of a radio wave absorbing material containing silicon carbide powder dispersed in matrix resin. Average particle diameter of the silicon carbide powder is 4-40 ?m. Silicon carbide powder content in the radio wave absorbing material is 15-45 volume %. Thickness of the radio wave absorbing layer is adjusted so that reflection attenuation of not less than 10 dB is provided in 76 GHz band.

Abstract: A soft hexagonal ferrite sintered material includes crystal particles of M-type hexagonal ferrite corresponding to a general chemical formula MFe12O19 wherein M is at least one element selected from the group consisting of Ba, Sr and Pb. Crystal particles having particle diameters of 5 &mgr;m to 100 &mgr;m are extracted from a sintered material produced from a precursor powder mixture. The extracted particles as seed crystals are mixed with a calcined powder comprising fine crystals having the above composition and particle diameters of 0.5 &mgr;m to 3 &mgr;m, then is sintered until the intended particle growth of the crystal particles in the sintered material is achieved to give an average particle diameter of 30 &mgr;m to 500 &mgr;m.