Subcutectic Densification and Second‐Phase Formation in Al 2 O 3 ‐Cao

The early and intermediate stages of densification of alumina containing calcia were examined at subeutectic temperatures. Up to 0.15 wt% calcia causes a decrease in the densification rate; from 0.15 to 0.7 wt% calcia, the densification rate increases initially but then decreases at longer times; more than 0.75 wt% calcia leads to a monotonically decreasing densification rate. The data for materials containing more than 0.15 wt% calcia may be interpreted as a competition between enhanced subeutectic densification and the presence of densification‐retarding second phases.