Sintering of α-Al2O3-seeded nanocrystalline γ-Al2O3 powders

This paper demonstrates that seeding nanocrystalline transition alumina powders is a viable option for producing high quality, alumina-based ceramics. By using α-Al2O3 concentrations of ⩾1.25 wt.% α-Al2O3 seed particles (equivalent to 5 ×1014 seeds/cm3 of γ-Al2O3) the sintering temperature is reduced from 1600°C for unseeded γ-Al2O3 to 1300–1400°C in dry pressed powders. The scale of the sintered microstructure is related to Nv−1/3 and thus a 100-nm grain size is obtained. It is apparent that seeding is necessary for producing dense, alumina-based ceramics from nanocrystalline transition alumina powders.