DIRECT OBSERVATIONS OF INTERFACE INSTABILITIES

Single crystals of lead bromide doped with silver bromide were grown b y the vertical Bridgman method. Direct observations were made in order to understand the interfacial instabilities. Numerical studies were c arried out to provide a framework for interpreting the observed convec tive and morphological instabilities. Observations on interfacial inst abilities in lead bromide with 500 and 5000 ppm silver bromide impurit ies supported the numerical results predicted for 1-g conditions. X-ra y rocking curves, X-ray contour scans, and etch-pit studies showed tha t increasing solutal convection deteriorated the crystal quality of th e crystals.