The reaction mechanism of Si₂-ZAlzOzN_8-z(Z=O, Si₃N₄) that was synthesized by carbothermal reduction and nitridation in SiO₂-C system was investigated on basis of the results of weight change, CO content, XRD analysis and thermodynamic calculation. It was suggested that Si3N4 was formed by following reactions.
SiO₂+C→SiO(g)+CO(g), SiO(g)+C+2N₂→Si₃N₄+CO(g)……………(at low temperature)
Si0₂+CO(g)→SiO(g)+CO₂(g), 3SiO(g)+3CO(g)+2N₂→Si₃N₄+CO(g)…(at high temperature)
SiC was formed at temperature above 1550°C. It was suggested that the formation of SiC occurred by following reactions.
Si₃N₄+3SiO₂→6SiO(g)+2N₂, SiO(g)+2C→SiC+CO(g)