Growth of bismuth and bismuth-antimony single crystals

Conditions have been identified that ensure unseeded growth of bismuth single crystals in air. The axial and radial (directed toward the crucible axis) temperature gradients necessary for the growth process, 40 and 6–7°C/cm, respectively, were produced using the axial-heat-flux-close-to-the-phase-interface (AHP) method. In the preliminary stage of experiments, a single-crystal ingot 40 mm in diameter and 60 mm in length has been obtained. Using a submerged heater that is used in the AHP method, we have developed an experimental procedure for measuring the curvature of the growth front directly in the crystal growth process. The results demonstrate that, for both pure bismuth and a bismuth-antimony alloy, its shape is uniquely determined by the temperature profile along the hot boundary of the melt layer from which the crystal grows. Even at a small superheating, ≃0.5–1.5°C, of the periphery of the submerged heater relative to its center, the growth interface is convex toward the melt during growth.