Abstract
The microstructural evolution during sintering of Al2O3 was investigated to determine the role of MgO additive, particularly when its concentration is very low ( 200 ppm). Compared to the specimen without MgO, a few Al2O3 grains were observed to grow enormously after the addition of 100 ppm MgO. When MgO content was increased to 200 ppm, however, a fine-grained homogeneous microstructure was obtained because many fast growing abnormal grains impinged each other. The promotion of abnormal grain growth by MgO was further supported by sintering the Al2O3 specimen in an MgO atmosphere. Contrary to the common sense, it is proposed that MgO is a grain growth promoter during sintering of alumina.
