A TRANSPARENT MULTIZONE FURNACE FOR CRYSTAL-GROWTH AND FLOW VISUALIZATION

A low-cost transparent multizone furnace for the crystal growth of low temperature materials and flow visualization is described. The furnac e consists of eight heating zones shaping thermal environments. The te mperature distribution between the ampoule and the furnace is measured and well controlled, so that a wide range of heating profiles can be specified. Due to the differences in the refractive indices of the fur nace, air, the ampoule, and the melt, the observed flow patterns and i nterface shapes during crystal growth in the system are optically dist orted. A procedure for correcting the distortion is also proposed. The zone-melting crystal growth of NaNO3 is used as an example to demonst rate the applications of the furnace. During crystal growth, natural c onvection in the melt zone is visualized using the laser light-cut tec hnique. After the lens effect is considered, the observed flow pattern s and interface shapes are compared with the calculated ones, and they are in good agreement.