β-Si3N4-α-Si3N4-Si2N2O系の1600℃以上における安定関係と加熱変化
1974 年 82 巻 950 号 p. 522-526
詳細
1974 年 82 巻 950 号 p. 522-526
Silicon nitride, Si3N4 and silicon oxynitride, Si2N2O are synthesized by nitriding highly pure and fine powder of silicon and silicon mixed with silica under atmospheric pressure of nitrogen in the range from 1400° to 1450°C. Heating experiments are performed with these samples in the range from 1530° to 1730°C in N2 atmosphere of 1 atm, and the change of composition is studied by X-ray diffraction. Pressed pellet of powdered mixture of α-Si3N4 and SiO2 shows a tendency to transform to β-Si3N4 by the heating. In these while, the formation of Si2N2O is observed together with large weight loss of the samples. Si2N2O changes to β-Si3N4 accompanying with the weight loss based on the evaporation of gas phase having nearly equal composition to SiO and nitrogen.
It is concluded from the results of experiments that the stable compound in the system, Si-N2(1 atm)-O2 changes in the order, β-Si3N4→Si2N2O→SiO2 according to the partial pressure of oxygen being increased. α-Si3N4 is unstable under these conditions. It is also mentioned that the gas phase, SiO has an important role in the oxidation process of Si3N4 and Si2N2O sintered articles at such elevated temperatures.
