Numerical Modeling Of Heat Transfer And Thermal Stress At The Czochralski Growth Of Neodymium Scandate Single Crystals

The Czochralski growth of NdScO3 single crystals along the [110]-direction is numerically analyzed with the focus on the influence of the optical thickness on the shape of the crystal-melt interface and on the generation of thermal stresses. Due to lack of data, the optical thickness (i.e., the absorption coefficient) is varied over the entire interval between optically thin and thick. While the thermal calculation in the entire furnace is treated as axisymmetric, the stress calculation of the crystal is done three-dimensionally in order to meet the spatial anisotropy of thermal expansion and elastic coefficients. The numerically obtained values of the deflection of the crystal/melt interface meet the experimental ones for absorption coefficients in the range between 40 and 200 m(-1). The maximum values of the von Mises stress appear for the case of absorption coefficient between 20 and 40 m(-1). Applying absorption coefficients in the range between 3 and 100 m(-1) leads to local peaks of high temperature in the shoulder region and the tail region near the end of the cylindrical part.