Convection in a Czochralski crucible – Part 2: rotating crystal

• Published in: Journal of crystal growth 2001, Vol.222 (1), p.356-364
• Main Authors: Hintz, P., Schwabe, D.
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from melts; zone melting and refining; Materials science; Methods of crystal growth; physics of crystal growth; Physics
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/S0022-0248(00)00885-X

We report on a convection experiment with a Pr=7 fluid. We study the instability of the flow driven by thermal buoyant convection, thermocapillary convection and forced convection due to crystal rotation. Flow visualization and thermocouple measurements are performed. A transition to oscillatory convection is found when the crystal dummy is rotated at a rate above some threshold value f C. f C was found to increase linearly with the temperature difference Δ T between the crystal dummy and the crucible but f C was found to be independent of the fluid depth H in the crucible. A strong influence of the meniscus geometry on f C was found. We report critical parameters for the transition to time-dependent flow and oscillation frequencies. The flow patterns under stable and unstable conditions are described. The unstable flow resembles a baroclinic instability which has been discussed before by other authors for such systems.