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 N_v^-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.