Si_3N_4-Al_20_3/Si_3N_4-Y_20_3 COUPLE DIFFUSION SYSTEM

摘要

The behaviour of the additives Al_2O_3 and Y_2O_3 on the microstructure of Si_3N_4 and Si_3N_4-ZrO_2 doped materials was studied using couple diffusion systems (Si_3N_4-Al_20_3/Si_3N_4-Y_20_3). After heat treat- ments, the line profile for Al and Y was determined. The secondary intergranular phases were identified by XRD and TEM analysis. The influence of the chemical composition of the intergranular glassy phase in the final microstructure after sintering was observed. The drastic effect of the Y_20_3 and ZrO_2 on the α-βSi_3N_4 transformation, β-Si_3N_4 average grain size, density and on the crystalline secondary grain boundary phases has been investigated.