Translucent alumina produced by slip-casting using a gypsum mold

Translucent Al2O3 ceramics could be successfully produced by slip casting u sing a gypsum mold, provided that CaSO4 impurities, which had penetrated in to the green compacts from the gypsum mold, were removed by the wash of cal cined compacts with HCl aqueous solution. Al2O3 ceramic samples were sinter ed at 1350 degreesC for 2 h under vacuum. The relative densities of the sin tered Al2O3 ceramic compacts with the HCl treatment were slightly higher th an those of the untreated samples. Grains in the HCl-treated samples grew h omogeneously with about 1 mum 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 fro m 0 to 12% as the wavelength increased from 300 to 900 nm.