Seedless Crystallization of Levitated Ge and GaSb Spherical Melts under Microgravity

Abstract

Seedless crystallization of Ge and GaSb melts was achieved under microgravity occurring in a drop-shaft capsule. It was observed that melts levitated in Ar atmosphere, formed into a spherical shape and were solidified instantaneously when they collided with the container quartz wall. X-ray diffraction pattern of these samples showed clear Laue spots signifying a single-crystal structure, while Ge or GaSb solidified in crucibles under normal gravity did not show Laue spots. These results indicate that single crystal growth rapidly occurs without seed crystals from the spherical melt under microgravity. This can be understood by assuming that an ordered structure like a single crystal is already formed in a levitated melt, and assists rapid crystallization when the melt touches the crucible wall and latent heat is deprived.