Submicrometer Transparent Alumina by Sinter Forging Seeded γ‐Al 2 O 3 Powders

Seeding boehmite with α‐Al 2 O 2 , followed by calcination at 600°C, results in an agglomerated alumina powder (<53 μm) that can be sinter forged to full density at 1250°C. Compressive strains as high as ɛ x =−0.9, and radial flow (ɛ x = 1.0) during sinter forging remove large, interagglomerate pores. The fully dense alumina has a grain size of 0.4 pm and is visually transparent. It is proposed that deformation of dense agglomerates is the primary mecha‐ nism responsible for large pore elimination and compact densification. The sinter forging of sol‐gel‐derived alumina powders offers a new technology to prepare highly transparent, optical ceramics at lower temperatures than conventional routes.