TY  - EJOU
AU  - Azoui, H.  
AU  - Bahloul, D.  
AU  - Soltani, N.  

TI  - Three-Dimensional Numerical Investigation of Convective Thermal Instabilities in the Sapphire Melt for Czochralski Growth Process
T2  - Fluid Dynamics \& Materials Processing

PY  - 2018
VL  - 14
IS  - 2
SN  - 1555-2578

AB  - In this work we have performed a three-dimensional numerical investigation in order to find the optimal conditions for growing efficiently high quality sapphire crystals with good thermal properties. We have studied thermal instabilities near the melt-crystal interface and the convective heat transfer under the Czochralski (Cz) process. We performed 3-D CFD simulation in cylindrical coordinates and used the Fast Fourier Transform method to analyze the temperature fluctuations. We present a detailed investigation on the effects of the crystal rotation speed and the temperature distribution on thermal instabilities of sapphire melt under forced convection. Where the melt forced convection, the radiative heat transfer and the Marangoni convection, were conducted for Al<sub>2</sub>O<sub>3</sub> melt in the Cz crucible. We have been able to determine the optimal rotation speed giving a planar crystal-melt interface where the symmetry of the flow in the crucible is conserved witch is found to be 13 rpm for the studied case. On the other hand we achieved a visualization of the temperature fluctuations just below the interface. These fluctuations give precious information about the melt -crystal interface, which plays an important role on the quality of the pulled crystal.
KW  - Forced convection
KW  -  thermal instabilities
KW  -  heat transfer
KW  -  temperature fluctuations
KW  -  sapphire
KW  -  crystal growth
KW  -  Czochralski technique

DO  - 10.3970/fdmp.2018.01149