Step Sintering of Microwave Heating and Microwave Plasma Heating for Alumina Ceramics

The invention of microwave induced plasma during microwave heating makes it possible to confine plasma inside a crucible, in the pressure range of 1.33 Pa to 0.5 MPa, and above 900℃. In this study, the step sintering of microwave heating and microwave plasma heating (SSMP) was proposed. In this process, microwave heating and plasma heating was ingeniously combined in one chamber, and vacuum was unnecessary for microwave-induced plasma. In the first step, the microwave energy directly heated alumina ceramics to a given temperature, above which microwave will mainly ionize the gas and sustain a plasma. Then the plasma further heated alumina ceramics to the final temperature to finish sintering. Maintaining the advantages of microwave heating and plasma heating, this step sintering approach will overcome the limitation of both processes for processing ceramics, and it will be suitable for sintering all kinds of ceramics in principle.