In-Situ Reactive Synthesis of Si2N2O Ceramics and Its Properties

Si2N2O is considered as a new great potential structural/functional material in place of Si3N4 for high-temperature applications. In the present work, Si2N2O ceramics were in-situ reactive synthesized by a nitridizing powder mixture of Si and SiO2 using an optimized two-step sintering process according to thermodynamic analyses. The results showed that the purity of Si2N2O in the produced ceramics increased with an increase in final sintering temperature, while the shrinkage and Vickers hardness decreased. After final sintering above 1923 K (1650 °C), pure nanograined Si2N2O ceramics can be obtained. Flexural strength and fracture toughness both showed peak values at 1873 K (1600 °C). The reaction mechanism was proposed and then the difference of the produced ceramics was discussed.