Double diffusive convection during growth of lead bromide crystals

Experiments were performed in controlled conditions to understand both morphological and convective instabilities and results were compared with the theoretical calculations. The sharp contrast between the solid (yellow) and the liquid (bright red) phases makes this transparent lead bromide a very suitable material for such an investigation. Crystals doped with 5000 ppm silver bromide were grown. The experimental observations agree with the preliminary results of the numerical prediction. Further, toroidal instabilities resulting from double diffusive convection were observed during crystal growth. Crystals for these interfacial observations were grown in a two zone vertical Bridgman furnace. The acoustic properties were better in doped rather than undoped crystals. Crystals were characterized by x-ray rocking curves and contour scans. Crystals grown at lower Rayleigh numbers showed better quality than crystals grown at higher Rayleigh numbers.