Computational Analysis of Radiative Heat Transfer in Czochralski Furnace and 3D Anisotropic Thermal Stress in Li₂MoO₄ Bulk Crystal

Abstract

Here, the radiative heat transfer inside a Czochralski furnace and the 3D thermal stress generated in a semitransparent Li2MoO4 crystal are deeply analyzed using anisotropic and temperature‐dependent elasticity and thermal expansion coefficients. The developed global numerical model takes into account induction heating, thermal conduction in all parts of the furnace, convection in the melt and the growth atmosphere, Marangoni convection at the free surface, radiation heat exchange between the furnace elements, internal radiation inside the semitransparent crystal and melt, and phase change at the growth interface. The contribution of each radiation mode is studied separately, then coupled together to clearly explain their roles in heat transfer, stress generation in the as‐grown crystal and in power consumption, and heat loss inside the furnace. Flow and temperature fields in the molten oxide and in the growth atmosphere as well as the thermal stress are presented and discussed for each case. Unrealistic cases are first considered where radiation exchange between the furnace elements and internal radiation in the assumed opaque crystal are neglected. For each case, the relation between temperature gradient and thermal stress is clearly demonstrated. Finally, the effect of the melt opacity on thermal stress is studied and related to temperature gradients in the crystal and at the free surface. The experimental observations are in good agreement.