As compared with conventional sintering, rapid heating in microwave system could enhance sinterability and final properties of alumina with a very short sintering time.
In this study microwave sintering was performed using zirconia brick as a reaction cavity which was positioned in 2.45GHz(700W) multimode microwave chamber. When power was supplied, the zirconia brick was heated first and the heating and sintering of alumina specimen was followed. The properties of sinterd alumina were compared with those of conventionally sintered alumina in the view of density and microstructure. Also the MgO effect and the effect of specific surface area in microwave sintering of alumina were investigated. Microwave sintered alumina showed high density and smaller grain size than conventionally sintered alumina becaus the ratio of densification rate/grain growth rate was increased by rapid heating. The MgO effect on alumina in microwave sintering was similar to that of conventional sintering results, and so grain growth was supressed. Alumina powder(AKP-50) compact with high specific surface area showed better sinterability in microwave sintering and within 5 minutes it reached the end point density, about 95%TD. It is evident that microwave heating has a great potential in sintering of alumina which has superior porperties.