Crucible for growing macrocrystals

Abstract

A crucible having an inner surface which is not wetted by a melt which shrinks when it solidifies, is provided with indentations in its walls, the indentatons located remote from its rim. The indentations are located beneath a lateral plane through the walls of the crucible, at about two-thirds (66.6%) of the vertical height of the walls, measured from the floor of the crucible, support an ingot grown in it. Supporting the crystal provides a gap between the bottom of the ingot and the inner surface of the bottom of the crucible. The gap allows more uniform heat transfer from the bottom of the crucible than is provided when there is no gap; the gap provides a controllable temperature gradient between the interior and exterior of the crucible. To direct propagation of the growth of a macrocrystal, the bottom of the crucible is provided with at least one set of multiple grooves in parallel relationship with each other. Preferably a second set of multiple grooves in parallel relationship with each other intersect the grooves of the first set at an angle chosen depending upon the lattice structure of the macrocrystal to be grown. A macrocrystal grown in a crucible with twin sets of angulated grooves produces single crystals. Grooves in the floor of a conventional graphite crucible are effective to produce an ingot with minimal multiplicities, if not an essentially single crystal, even if essentially continuous contact of the bottom of the ingot with the floor is broken.