Production of sapphire tubes for high‐pressure sodium lamps using the stepanov method at high rates of growth

Abstract

Abstract The process of the Stepanov growth of sapphire tubes is studied at the growth rates up to 20 mm · min −1 in a Mo crucible with graphite succeptor. It is established that the main factor preventing the production of high‐quality samples is contamination of the melt due to the gas transport reactions the growth chamber atmosphere and formation of oversaturated carbon solid solution in the Al 2 O 3 matrix. The decomposition of this solid solution gives rise to the second‐phase‐particle precipitations. The production of highquality sapphire tubes at the growth rates up to 20 mm · min −1 is possible with a careful elimination of water vapours and oxygen from the growth chamber atmosphere.