ムライトの焼結及び微構造に及ぼすY_2O_3添加の影響(第1報) : 相変化と焼結性  [in Japanese] Effects of Y_2O_3 Addition on the Sinterability and Microstructure on Mullite (Part 1) : Phase Transformation and Sinterability  [in Japanese]

The effect of addition of Y_2O_3 on the sinterability and microstructure of mullite was studied by differential thermal analysis, X-ray powder diffraction, scanning and transmission electron microscopy, and dilatometry. The mullite powder compacts containing 2-10 wt% Y_2O_3 were sintered at 1500℃ in air. The solid state reaction of Y_2O_3 and mullite during the sintering process produced some crystalline phases of yittrium silicates and α-Al_2O_3. The product phases were dependent on the amount of Y_2O_3 addition. The yittrium silicate and Al_2O_3 melted into a liquid phase at higher sintering temperature, which enhanced the sinterability of mullite powders. During the furnace cooling process, the liquid phase crystallized, and different crystalline phases were obtained depending on the amount of Y_2O_3.