Si₃N₄-Er₂O₃-CaO-Al₂O₃常圧焼結体の組織と室温機会的性質

抄録

The optical and SEM microstructures and the room temperature mechanical properties of Si₃N₄-Er₂O₃-CaO-6 mol%, Al₂O₃ compact sintered under 0.1 MPa of nitrogen gas at 1973-2073 K for 3.6 ks were mainly investigated as a function of Er₂O₃ (2, 4, 8 mol%) and GaO (0-10 mol%) contents.
The results obtained were as follows; (1) The additions of Er₂O₃ and CaO to Si₃N₄-Al₂O₃ compact increased the relative density. (2) The a-β phase transformation and the grain growth of Si₃N₄ phase were restricted with increasing CaO content. (3) The crystalline grain boundary phases in Si₃N₄-8 mol%Er₂0₃-CaO-A1₂O₃ compact were found to be mainly Er₄Si₂O₇N₂ and Er₂Si₃O₃N₄ at small and large CaO contents, respectively. (4) The transverse-rupture strength showed a maximum generally at about 8 mol%Er₂O₃ and 2 mol%CaO. The hardness increased with increasing CaO content. The result on the strength was discussed in relation to the relative density, grain size, kinds of grain boundary phases, fracture toughness, fracture source, etc.