| dc.description.abstract | The thermal and flow transport in a Czochralski crystal growth furnace plays an important role to effect the single crystal growth quality of sapphire. However, the thermal and flow fields in the melt of the single crystal growth process are difficult to observe in experimental study. This thesis has numerically investigated the thermal and flow transport phenomenons using the finite volume method via CGSim software. The electromagnetic, thermal, and fluid fields during the sapphire single crystal growth process have been investigated. The temperature and flow fields inside the furnace are coupled with the heat generation in the Iridium crucible which is generated by the electromagnetic field using the RF coil.
For different stages of Czochralski crystal growth of sapphire, the configuration usually used in a real Czochralski crystal growth process consists of a crucible, induction coil, insulation, crystal, melt and gas. At first the volumetric distribution of heat generation inside the metal crucible is calculated. Using this heat distribution as a source the fluid flow and temperature fields in the whole system are computed. After that, thermal analysis is computed only in the crystallization zone, including the crystal, melt, crucible, and a gas region around the crystal. The computation in the crystallization zone involves the turbulent flow of the sapphire melt, the laminar gas flow, and radiative heat exchange in the semitransparent crystal.
Then using the temperature distribution in a single crystal to calculate thermal stress via COMSOL software. The anisotropy of elastic constants and thermal expansion coefficients are considered in the problem. The analyses are performed both for the pulling directions of a-axis and c-axis.
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