A visualization and computational study of horizontal Bridgman crystal growth

A transparent three-zone horizontal Bridgman furnace was used for the cryst al growth of sodium nitrate. During crystal growth, the heating profiles an d the growth front shape as well as flow patterns were recorded. To further understand the heat flow, a three-dimensional computer model based on an e fficient multigrid finite volume method was also used to simulate the growt h. Key process parameters, including the heating profiles, the growth rate, and the booster heating, were considered and their effects on the interfac e shape and the flow structures were discussed. It was observed that both b uoyancy and Marangoni flows were dominant in the melt causing a highly conc ave interface. As a result, single-crystal growth was very difficult, Suita ble insulation at the furnace bottom reduced interface deflection. Further, interface inversion was obtained by using a booster healing while keeping a cold spot at the top furnace wall near the interface by blowing cooling a ir. The obtained convex interface shape thus made the growth of a single cr ystal much easier. (C) 2000 Elsevier Science B.V. All rights reserved.