The effect of MgO additive to the sintering of very fine a-A1203 was discussed in this experiment. The continuous shrinkage during sintering was observed in the special high temperature dilatometer, and the grain size of sintered compact was obtained from the electron micrograph.
The investigation shows :
1) The temperature at which the shrinkage begins, supposedly it is nearly equal to the initiation of the sintering, was slightly lowered by the MgO addition. This was found about 900-1000°C, the same at which the spinel formation between Al₂O₃-MgO occured.
2) The shrinkage increased by adding MgO, while the timerate of shrinkage at isothe-rmal holding was found to become decreased.
3) The increased grain growth was observed by the addition of MgO. And, the higher the sintering temperature, the greater the effectiveness of MgO addition.
By these three observations, the accelerating effectiveness of MgO to the sintering of Al₂O₃ was confirmed experimentally.