SUBMICROMETER TRANSPARENT ALUMINA BY SINTER FORGING SEEDED GAMMA-AL2O3 POWDERS

Seeding boehmite with alpha-Al2O3, followed by calcination at 600 degr ees C, results in an agglomerated alumina powder (<53 mu m) that can b e sinter forged to full density at 1250 degrees C. Compressive strains as high as epsilon(z) = - 0.9, and radial how (epsilon(r) = 1.0) duri ng sinter forging remove large, interagglomerate pores. The fully dens e alumina has a grain size of 0.41 mu m and is visually transparent. I t is proposed that deformation of dense agglomerates is the primary me chanism responsible for large pore elimination and compact densificati on. The sinter forging of sol-gel-derived alumina powders offers a new technology to prepare highly transparent, optical ceramics at lower t emperatures than conventional routes.