Two kinds of roles of MgO in the densification and grain growth of alumina under various atmospheres: Sensitive and insensitive roles to the experimental procedures

Two kinds of high-purity Al₂O₃ powder were studied with respect to the effects of not only MgO doping but also atmosphere on both densification and grain growth. Controversial results for MgO doping are explained in terms of two roles that MgO can play during these processes: sensitive and insensitive to the experimental procedures. Atmospheres, whether dry or wet, had little influence on densification or grain growth in the early stage. After closed pores appreciably formed, however, both N₂ and Ar atmospheres quickly reduced the densification rate.