Along with the recent increase in consumption of sapphire single crystals, the alumina green body of high-purity and highdensity is required. The current manufacturing process for high-purity alumina using the aluminum or aluminum alkoxide compounds as a starting material had difficulties in mass production accompanied by the expensive equipments with high maintenance costs. Compared to this method, the high-purity alumina can be produced using the aluminum hydroxide dissolved in a caustic soda (sodium hydroxide) solution, in large quantity, with low cost. The mixing solution is aged for a certain period of time and then small amount of adsorbent is applied to selectively remove impurities in the solution. Finally a high purity alumina can be made from the refined solution. The alumina powders obtained through this method can be compacted and fired without any organic binder for the production of high-purity and high-density alumina green body. In this study, parameters in the manufacturing process employing the aluminum hydroxide to produce high-purity alumina were explored. And property changes of the final products were examined by varying the forming and firing parameters.

Keywords: Sapphire single crystal, Alumina green body, Aluminum hydroxide, Hydrothermal method, Green density.