Abstract
Sapphire is an important crystal that finds application in a number of high technology optical applications. For optical applications a high transparency is essential. Several defects/imperfections are present in the surface layer of ‘as grown’ sapphire crystal. These defects/imperfections can be removed by polishing the sapphire crystals. The high hardness and strength of sapphire necessitates the use of high machining and polishing forces. Conventional polishing techniques are unable to meet this requirement. Specialised techniques have been developed to obtain optical flatness and low scatter surface finish. These techniques are reviewed and compared in this article.
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