Fabrication of Transparent, Sintered Sc2O3 Ceramics

We report here the fabrication of transparent SC 2 O 3 ceramics via vacuum sintering. The starting SC 2 O 3 powders are pyrolyzed from a basic sulfate precursor (Sc(OH) 2.6 (SO 4 ) 0.2 . H 2 O) 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 Sc 2 O 3 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°C, at which the resultant Sc 2 O 3 powder is ultrafine (∼ 85 nm), well dispersed, and almost free from residual sulfur contamination. With this reactive powder, transparent Sc 2 O 3 ceramics having an average grain size of ∼9 μm and showing a visible wavelength transmittance of ∼60-62% (∼76% of that of Sc 2 O 3 single crystal) have been fabricated via vacuum sintering at a relatively low temperature of 1700°C for 4 h.

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