Si₃N₄-Y₂O₃-Al₂O₃常圧焼結体の組織と室温強度

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.