Modeling and crystal growth of semi-transparent rare earth halides

The goal of this study is to (i) determine the factors that contribute to large thermal stresses and cracking of rare earth halide crystals, and (ii) to eliminate cracking of these crystals as the diameter is increased. A solidification model for the growth of rare earth halides was developed, which captures the effects of heat transfer including melt convection. An important element in solidification modeling of these materials is radiation heat transfer. The heat transfer model incorporates the spectral and thermal dependence of the crystal's absorption characteristics. Material properties, necessary for modeling, were measured. The model uses an axially symmetric geometry representing the crystal growth ampoule and calculates the shape of the solid–liquid interface, temperature gradients and thermal stresses.