MARANGONI CONVECTION AND ENHANCED MORPHOLOGICAL STABILITY IN FLOAT-ZONE TRAVELING SOLVENT CRYSTAL-GROWTH OF LAB6

We analyze the problem of onset of morphological instability and the i ncreasing supersaturation gradient in the particular case of float-zon e traveling solvent growth of LaB6 crystals in excess of La, taking in to account the actual liquidus line on the relevant phase diagram of S torms and Mueller [J. Phys. Chem. 82, 51 (1978)]. We show that the act ion of Marangoni convection decreases the concentration gradient at th e solidification interface and inhibits the morphological instability and the increasing supersaturation gradient. We suggest that this effe ct allows the implementation of float-zone traveling solvent growth of LaB6 crystals with pulling rates of congruent to cm/h without the app earance of defects structures associated with the morphological instab ility and increasing supersaturation gradient. (C) 1996 American Insti tute of Physics.