Performance of magnesium oxide-silicon carbide composites with microwave attenuation characteristics in the X wave band

The MgO based lossy buttons with the addition of SiC were manufactured by a hot-pressing method and the microwave attenuation characteristics in the X wave band (8-12 GHz) were tested using a network analyzer. The effects of the content of SiC, sintering temperature, holding time, and dielectric properties on the microwave characteristics were investigated. The results show that when the content of SiC is in the range from 1% (mass fraction, the same below) to 10%, the attenuation frequency of lossy resonance (f₀) shifts to a low frequency as the effective attenuation bandwidth grows, and this effect is stronger when the content of SiC is less than 2%. Lowering the sintering temperature raises f₀, but the holding time has little effect on the frequency. It is found that the relative dielectric constant (ε_r) is the main factor affecting f₀ in accordance with the analysis of the resonance cavity and the property of the wave-guide. In addition, the relationship between f₀ and ε_r under the given radius is introduced, according to which the lossy buttons in the coupling cavity of the traveling wave tube is discussed from the viewpoint of material design.