Microwave sintering and kinetic analysis of Y2O3–MgO composites

To obtain fine grained Y2O3–MgO composites for infrared application, the kinetics of Y2O3–MgO nanopowders (~50 nm) during microwave sintering process was analyzed to track details of densification evolution. Finer structure and higher density were exhibited during microwave sintering process compared with conventional sintering process. The values of grain growth exponent n indicate that grain boundary diffusion is the main migration mechanism for microwave sintering when sintering temperature is below 1300 °C, while volume diffusion and grain boundary diffusion coexist at higher temperature (1400 °C). The calculated grain growth activation energy of microwave sintered samples (108.22 kJ/mol) is much lower than that of conventional sintered ones (160.42 kJ/mol), indicating that microwave sintering process can effectively promote the densification. Based on the kinetic analysis data, microwave sintering parameters were optimized, and Y2O3–MgO composites with an average grain size of ~300 nm and Vickers hardness of 11.2±0.3 GPa were obtained.