A low-cost transparent multizone furnace for the crystal growth of low temperature materials and flow visualization is described. The furnace consists of eight heating zones shaping thermal environments. The temperature 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 furnace, air, the ampoule, and the melt, the observed flow patterns and interface shapes during crystal growth in the system are optically distorted. A procedure for correcting the distortion is also proposed. The zone-melting crystal growth of NaNO3 is used as an example to demonstrate the applications of the furnace. During crystal growth, natural convection in the melt zone is visualized using the laser light-cut technique. After the lens effect is considered, the observed flow patterns and interface shapes are compared with the calculated ones, and they are in good agreement.
