Liquid Phase Sintering Behavior of Amorphous Nano-sized Silicon Nitride Powders

摘要

The amorphous nano-sized silicon nitride powders were sintered by liquid phase sintering method. Si_3N_4-Si_2N_2O composites were in-situ fabricated. The Si_2N_2O phase was generated by an in-situ reaction 2Si_3N_4(s)+1.5O_2(g)=3Si_2N_2O(s)+N_2(g). The content of Si_2N_2O phase up to 60% was obtained at a sintering temperature of 1650℃and reduced when the sintering temperature increased or decreased, which indicates that the reaction is reversible. The mass loss, relative density and average grain size increase with increasing of sintering temperature. The average grain size is less than 500nm when the sintering temperature is below 1700℃. During the sintering procedure, there is a complex crystallization and phase transition: amorphous Si_3N_4 → equiaxial α-Si_3N_4→ equiaxial β-Si_3N_4 → rod-like Si_2N_2O → needle-like β-Si_3N_4. Small round-shaped β-Si_3N_4 particles are entrapped in the Si_2N_2O grains and a high density of staking faults are situated in the middle of Si_2N_2O grains at a sintering temperature of 1650℃.