| To develop a process of silicon nitride based ceramics for radome application is the fundamental goal of the present study. Besides its superior high-temperature mechanical performance, the dielectric properties and coefficient of thermal expansion are also excellent. It was significant for both theoretics and application if the reliability of its dielectric properties increases.All kinds of sintering aids are chosen and the influence of them on properties and process of sintered Si3N4 ceramics is investigated. Research has shown that composite aids are more effective than single aid to sintered Si3N4 ceramics, MgO—Al2O3—SiO2 composite aid have been taken into account.Nanometer powder was brought into the Si3N4 sintering process in order to decrease the sintering temperature. There is a difference between this process and traditional one. The addition of nanometer powder could affect bimodal particle size distribution.2MgO·2Al2O3·5SiO2 and LiCO3·Al2O3·4 SiO2 were added as sintering additive to improve Si3N4 sintering performance and to overcome the effect on dielectric (dielectric constant and dielectric loss) and thermal properties. We had founded a system about N-raw,W-raw,MAS,LAS and sintering surrounding.The mechanical properties, dielectric properties and microstructure of the ceramic materials prepared from different starting powder were investigated in comparison method. In the conclusion,it is the best methods,(Si3N4:additives=7:3),sintering at 1550℃。...
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