A microwave method for the preparation and sintering of β′-SiAlON

A microwave-assisted carbothermal reduction and nitridation (CTR/N) method has been used for successful preparation of monophasic β′-SiAlON starting from kaolinite and carbon black. Phase pure β′-SiAlON has been obtained in under 60 min in microwave field. The z value of microwave prepared β′-SiAlON is found to be 2.95, which is very close to the expected value from kaolinite composition. Formation of β′-SiAlON has been monitored with XRD and MASNMR of 29Si and 27Al; the possible reaction mechanism has been discussed. Kaolinite to β′-SiAlON conversion appears to be a very rapid single-step reaction under microwave irradiation. β′-SiAlON powders have been microwave sintered to 98.7% of theoretical density in 30 min.