IMPROVEMENTS IN OR RELATING TO CRYSTALLIZATION APPARATUS

1,248,007. Crystal pulling. GOSUDARSTVENNY NAUCHNO-ISSLEDOVATELSKY I PROEKTNY INSTITUT REDKOMETALLICHESKOI PROMYSHLENNOSTI. 18 Dec., 1969, No. 61808/69. Heading BIS. In a crystal pulling apparatus comprising a vacuum chamber 1 and a heatable crucible 5 located at the bottom thereof, there is provided an internally cooled crystal holder 28 which is rotatable and vertically reciprocable, and a sealing member 2 for sealing the space above the crucible when the remainder of the chamber is open to ambient pressure. The cooling device comprises pipe 25 for supplying compressed air to radially disposed ducts 40, at the end of each of which is a vortex-type turbulence nozzle 41. A throttle valve is located at the end of pipe 43, one for each duct, and the open end of pipe 43 is directed onto the holder 28. Air passing through this nozzle and valve becomes cooled. Excess air escapes from pipe 44 through an adjustable, perforated cap 45. The crucible, immersed in a liquid thermostat 8, may be connected via an intermediate evacuated chamber 6 to a further supply of melt in another evacuated chamber 17, which is sealable at 16 from chamber 16. Chamber 17 is sealable from the atmosphere when connected to the crucible via chamber 6. The crystallization of gallium with impurities less than 10-7% by wt. in the product is specified.