Yttrium Oxide-Assisted CRN Synthesis of Silicon Oxynitride Powders with Controlled Morphology

Si₂N₂O powders were synthesized at low temperatures by a Y₂O₃-assisted-carbothermal reduction nitridation (CRN) with mesoporous silica/carbon composite as raw material. Experimental results showed that with the addition of Y₂O₃, the CRN reaction temperature decreased from 1380°C to 1250°C. The mechanism for Y₂O₃ reducing the CRN temperature was discussed in detail. It was found that the occurrence of Si₂N₂O at low temperatures was due to the formation of an eutectic intermediate phase as Y₂SiO₅, which was the reaction product of Y ₂O₃ and mesoporous SiO₂. In addition, spherical and rod-like Si₂N₂O powders were found to be readily obtained by selecting the mesoporous silica/carbon composite precursors with mesoporous silica spheres and rod-like SBA-15, respectively.