抄録
The microstructure and room temperature transverse-rupture strength of Si3N4-Y2O3-Al2O3 compacts sintered under 0.1 MPa of nitrogen were mainly investigated as a function of contents of Y2O3 (2-20 mol%) and Al2O3 (6-17 mol%).
Two kinds of crystalline grain boundary phases (YSiO2N and Si3N4⋅Y2O3) were formed, according to the contents of Y2O3 and Al2O3. The compact showed the highest strength (1.0 GPa) nearly at the composi-tion of 8 mol%Y2O3 and 6 mol%Al2O3. This would mainly be attributed to the facts that the compact had high relative density and that it was almost free from both large pores acting as a fracture source and a large domains of Si2N4⋅Y2O3 phase.
