Method of enhancing the optical transmissivity of polycrystalline alumina bodies, and article produced by such method

In the manufacture of a translucent body of polycrystalline alumina that is formed by (a) compressing or extruding a mixture of high-purity alumina powder, a selected small amount of magnesia and a suitable binder into a green porous compact of the desired shape, (b) pre-sintering the green compact in an oxygen-containing atmosphere at a predetermined temperature and for a sufficient period of time to remove the binder, and then (c) sintering the compact in a vacuum or a hydrogen atmosphere at a predetermined higher temperature for a period of time sufficient to convert the compact into a dense ceramic body of polycrystalline alumina, the method of enhancing the optical transmissivity of said polycrystalline alumina body comprising;

• preparing an aqueous slurry that contains a predetermined quantity of finely-divided alumina particles,
• placing the green porous compact in contact with the aqueous slurry so that the slurry is absorbed by the compact and thus enters the pores and coats the surface of the compact,
• drying the slurry-impregnated-and-coated green compact and thereby depositing finely-divided alumina particles in the pores and interstitial surface cavities of the compact, and then
• sequentially subjecting the slurry-impregnated-and-coated green compact to the pre-sintering and sintering operations so that the slurry-deposited alumina particles become integral fused parts of the finished polycrystalline alumina body and improve the optical transmissivity thereof by virture of the pore-filling and surface-leveling-and-smoothing effects produced by said slurry-deposited alumina particles.