High transmittance and grain-orientated alumina ceramics fabricated by adding fine template particles

Transparent Al₂O₃ ceramics with grains aligned to the c-axis were prepared by adding platelets with a low aspect ratio into fine equiaxed particles. The mixed powders were formed into green bodies using spontaneous coagulation casting and sintered by pressureless sintering and hot-isostatic pressure sintering. Zeta potentials and rheological behavior of the slurries, relative densities of green bodies, and orientation and optical properties of sintered bodies were investigated and discussed. The platelet with a high aspect ratio suppressed densification more seriously during sintering than the one with a low aspect ratio. An excellent oriented structure was obtained when 5 wt% platelets with a low aspect ratio were added, and transparent Al₂O₃ ceramics with grains aligned to c-axis were successfully prepared; the in-line transmittance was 78.4% at 600 nm, which is the highest one in the currently reported literature.