Numerical study of heat transport and fluid flow during different stages of sapphire Czochralski crystal growth

For different stages of Czochralski crystal growth of sapphire, the flow and temperature field have been studied numerically using the finite element method. The configuration usually used in a real Czochralski crystal growth process consists of a crucible, active afterheater, induction coil with two parts, insulation, crystal, melt and gas. At first the volumetric distribution of heat generation inside the metal crucible and afterheater was calculated. Using this heat distribution as a source the fluid flow and temperature field in the whole system as well as the crystal–melt interface were computed. It was shown that during the last stage of the growth process, the temperature maximum of the system is located at the crucible free surface and the crystal–melt interface has the highest deflection toward the melt.