Preparation and properties of silicon nitride-phosphate composites for application in microwave furnace

Abstract

Si3N4 ceramic is one of the most promising microwave metallurgy furnace materials because of the outstanding mechanical, relatively low dielectric properties and excellent thermal shock resistance. However, the difficult sintering of Si3N4 ceramics extremely restrict their large-scale application in the field of refractories for microwave metallurgy. In this work, silicon nitride-phosphate ceramics were fabricated by introducing aluminum phosphate or chromium phosphate aluminum into Si3N4 ceramics at 1500 °C. The effect of the amount of aluminum phosphate and chromium phosphate aluminum on sintering performance and dielectric properties was investigated. The results showed that the addition of aluminum phosphate or chromium phosphate aluminum could promote sintering, and the mechanical and dielectric properties of Si3N4 ceramics were efficiently improved. The Si3N4-aluminum phosphate composites exhibited better sintering performance (higher density and mechanical property) than that of Si3N4-chromium phosphate aluminum composites. Meanwhile, the dielectric constant and dielectric loss of Si3N4-chromium phosphate aluminum composites were better than Si3N4-chromium phosphate aluminum composites.