DEVICE FOR GROWING SAPPHIRE MONO-CRYSTALS Russian patent published in 2004 - IPC

FIELD: growing sapphire mono-crystals from melts; updating of thermal protection of system. SUBSTANCE: proposed device includes vacuum chamber, crucible with mold, cylindrical resistive heater made from tungsten bars and mounted coaxially relative to crucible, cylindrical reflector, vertical shield in form of molybdenum cylinders fastened together and upper and lower horizontal shields. Reflector consists of two pairs of coaxial molybdenum cylinders whose inside cavities are filled with high-melting material; ratio of external diameter of crucible to inner diameter of cylindrical pairs of reflector ranges from 1: (1.6-1.8) : (2.0-2.2) respectively; distance between bars of heater and axis of chamber is equal to 0.65-0.75 of chamber radius. Pairs of reflector cylinders are sectional in height; cavities of pairs of reflector cylinders are filled with tungsten bars and/or tungsten powder, and/or molybdenum sponge and/or molybdenum sponge with addition of mixture of powders of molybdenum and tungsten. EFFECT: possibility of growing crystals of 20 kg at retained quality; low cost of thermal protection system. 3 cl, 3 dwg