GROWTH OF SHAPED SAPPHIRE CRYSTALS USING AUTOMATED WEIGHT CONTROL

The automated control systems have been developed for the growth of va rious sapphire crystals by edge-defined film-fed growth (EFG) and nonc apillary shaping (NCS) methods. Automated crystal weight control is ba sed on the analysis of the behaviour of the mass rate deviation at all stages of the growth process (seeding, crystal expansion, stationary growth, in-situ cross-sectional changing). The maintenance of the mass rate deviation in a certain range provides the crystal quality contro l as well as crystal shape control.