Large-size CeF3 Crystal Growth by Heat Exchanger-Bridgman Method: Thermal Field Design and Optimization

With the continuous development of CeF3 crystals in laser and magneto-optical applications, the demand for CeF3 single crystals with large size and high optical quality has become increasingly urgent, while the high viscosity and low thermal conductivity of CeF3 melt always bring challenges to crystal growth process. In order to study the growth problem caused by low thermal conductivity of CeF3 melt, the influence mechanism of the furnace structure and process parameters on temperature distribution and crystallographic interface during the growth process was explored. In this work, numerical simulations about the growth of large size CeF3 crystal (phi 80 mm) through the heat exchanger-Bridgman method were carried out to analyze the relationship between furnace structure and crystal/melt temperature distribution, the variation of interface shape in different growth stages, and the mechanism of thermal field structure on the growth interface. Results show that when the length of the heating element matches the length of the crucible, it is more conducive to construct a reasonable temperature gradient field. The unfavorable concave interface during the "shouldering" and "cylindering" growth stages can be effectively improved by adjusting temperature distribution on the ampoule wall through changing the baffle shape and adding a reflective screen. Therefore, the result not only deepens understanding of the crystallization habit of CeF3 crystals, but also enlightens the furnace and growth interface optimization of other crystals' Bridgman growth.