Polycrystalline alumina ceramics doped with nanoparticles for increased transparency

Transparent alumina samples were prepared by the gelcasting process followed by pressureless presintering and hot isostatic pressing. High transparency was obtained by doping alumina powder with zirconia and spinel nanoparticles. The doping approach enabled accommodating 0.3 wt% zirconia and 0.175 wt% spinel nanoparticles without any light scattering. The doping combined with colloidal processing resulted in grain size refinement in a fully dense microstructure and adequate in-line transmission improvement. The maximum in-line transmission reached 70.4% at a wavelength of 632.8 nm and a sample thickness of 0.8 mm and was at the theoretical maximum in the infrared wavelength range between 2000 and 4000 nm. The presented processing approach featured near-net shape and scale-up capabilities.