Translucent alumina produced by slip-casting using a gypsum mold

Translucent Al2O3 ceramics could be successfully produced by slip casting using a gypsum mold, provided that CaSO4 impurities, which had penetrated into the green compacts from the gypsum mold, were removed by the wash of calcined compacts with HCl aqueous solution. Al2O3 ceramic samples were sintered at 1350 °C for 2 h under vacuum. The relative densities of the sintered Al2O3 ceramic compacts with the HCl treatment were slightly higher than those of the untreated samples. Grains in the HCl-treated samples grew homogeneously with about 1 μm in diameter. The sintered Al2O3 ceramics with the HCl treatment were translucent. Transmittance values were measured by spectroscopy. Transmittance values in the HCl-treated samples increased from 0 to 12% as the wavelength increased from 300 to 900 nm.