Undercooling and solidification of Si by electromagnetic levitation

Pure Si droplets were containerlessly undercooled using an electromagnetic levitation method. An undercooling up to 330 K prior to solidification has been reproducibly achieved for bulk samples in size of 10 mm. A transition from faceted growth at lower undercoolings to continuous growth at higher u ndercoolings was observed through analyses of changes in phase morphologies on the surface of the samples. The transition was caused by existence of a large kinetic undercooling. The nucleation frequency and the crystal/melt interfacial energy are discussed within the frame of Spaepen's model in ter ms of the structure of the interface. (C) 2001 Acta Materialia Inc. Publish ed by Elsevier Science Ltd. All rights reserved.