Reaction and Formation of Crystalline Silicon Oxynitride in Si–O–N Systems under Solid High Pressure

Abstract

Oxidized amorphous Si3N4 and SiO2 powders were pressed alone or as a mixture under high pressure (1.0–5.0 GPa) at high temperatures (800–1700°C). Formation of crystalline silicon oxynitride (Si2ON2) was observed from amorphous silicon nitride (Si3N4) powders containing 5.8 wt% oxygen at 1.0 GPa and 1400°C. The Si2ON2 coexisted with β‐Si3N4 with a weight fraction of 40 wt%, suggesting that all oxygen in the powders participated in the reaction to form Si2ON2. Pressing a mixture of amorphous Si3N4 of lower oxygen (1.5 wt%) and SiO2 under 1.0–5.0 GPa between 1000° and 1350°C did not give Si2ON2 phase, but yielded a mixture of α,β‐Si3N4, quartz, and coesite (a high‐pressure form of SiO2). The formation of Si2ON2 from oxidized amorphous Si3N4 seemed to be assisted by formation of a Si–O–N melt in the system that was enhanced under the high pressure.