Numerical Analysis of Sapphire Single Crystal Growth Using the Vertical-Horizontal Gradient Freezing (VHGF) Method

摘要

A sapphire single crystal growth process by the Vertical-Horizontal Gradient Freezing (VHGF) method was studied by a numerical analysis technique. The heater power was controlled in order to follow the given arbitrary target heater temperature profile through the whole series of the process. Due to the influence of radiation heat transfer, the heater had spatial temperature deviation in spite of the fact that the heater power was imposed uniformly through its whole body. As a structural feature of the VHGF method, temperature at the lower part of crucible was lower than that at the upper part of crucible because it was cooler at the bottom of the furnace. Thus, the movement of the solid/liquid interface was driven in the bottom-to-top direction.