Fabrication of transparent, sintered Sc2O3 ceramics

We report here the fabrication of transparent Sc2O3 ceramics via vacuum sintering. The starting Sc2O3 powders are pyrolyzed from a basic sulfate precursor (Sc(OH)(2.6)(SO4)(0.2)center dot H2O) precipitated from scandium sulfate solution with hexamethylenetetramine as the precipitant. Thermal decomposition behavior of the precursor is studied via differential thermal analysis/thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffractometry, and elemental analysis. Sinterability of the Sc2O3 powders is studied via dilatometry. Microstructure evolution of the ceramic during sintering is investigated via field emission scanning electron microscopy. The best calcination temperature for the precursor is 1100 degrees C, at which the resultant Sc2O3 powder is ultrafine (similar to 85 nm), well dispersed, and almost free from residual sulfur contamination. With this reactive powder, transparent Sc2O3 ceramics having an average grain size of similar to 9 mu m and showing a visible wavelength transmittance of similar to 60-62% (similar to 76% of that of Sc2O3 single crystal) have been fabricated via vacuum sintering at a relatively low temperature of 1700 degrees C for 4 h.