Experimental observation of the influence of furnace temperature profile on convection and segregation in the vertical Bridgman crystal growth techniqueAzulene-doped naphtalene was directionally solidified using the vertical Bridgman-Stockbarger technique. Doping homogeneity and convection are determined as a function of the temperature profile in the furnace and the freezing rate. Convective velocities are two orders of magnitude lower when the temperature increases with height. The cross sectional variation in azulene concentration tends to be asymmetric. Neither rotation of the ampoule nor deliberate introduction of thermal asymmetries during solidification had a significant influence on cross sectional variations in doping. It is predicted that slow directional solidification under microgravity conditions can produce greater inhomogeneities than on earth. Thus when low freezing rates are necessary in order to avoid constitutional supercooling, it may be necessary to combine microgravity and magnetic fields in order to achieve homogeneous crystals.
Document ID
19910029371
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Neugebauer, G. T. (II-VI, Inc. Saxonburg, PA, United States)
Wilcox, W. R. (Clarkson University Potsdam, NY, United States)