METHOD OF GROWING STAR-SHAPED SINGLE CRYSTALS OF REFRACTORY OXIDES BY VERNEUIL METHOD Russian patent published in 1998 - IPC

FIELD: production of crystals of sapphire and ruby with asterism effect by Verneuil method. SUBSTANCE: method includes supply of mixture which consists of aluminum oxide, titanium dioxide and coloring addition to crystallization chamber through central channel of two-channel nozzle burner with coaxial channels; supply of hydrogen and oxygen; melting of mixture in zone of front of crystallization and growing of inoculating crystal and subsequent roasting of produced crystal. In so doing, supplied through peripheral channel of burner is explosive mixture of hydrogen and oxygen at their percentage ratio of 100:50; and supplied through central channel additionally at excessive pressure with respect to explosive mixture is oxygen with provision of oxidizing atmosphere in zone of mixture melting. Total hydrogen-oxygen ratio equals from 100:51 to 100:60. Mixture contains titanium dioxide on basis of aluminum, oxide in the amount of TiO₂ = 0.4-1.0 wt.%. Single crystal is grown at temperature of 2,030-2,100 C with temperature drop between crystallization front and internal wall of crystallization chamber of not exceeding 100 C and rate of crystal growth is preset from the range of 0.7 to 2.0 mm/h with reverse relationship on concentration of titanium dioxide. EFFECT: higher optical properties of crystal such as transparence, saturated color and increased asterism effect. 3 cl