Pore defects related to slurry character and their relevance to strength distribution in alumina ceramics

A significant difference of strength distribution was noted for alumina ceramics made through powder granule compaction starting with dispersed and flocculated slurry. To investigate the origin of the change, the structures of both intermediate and sintered bodies were examined. Dimples and large pores were observed in the granules made from the dispersed slurry, whereas no dimple structure was obtained from flocculated slurry. The granule defects were responsible for major defects in powder compacts, which were not eliminated during sintering. As a result, the slurry character strongly influenced the defect structure in the final sintered parts, which governed the strength distribution of ceramics.