Technique for controlling temperature uniformity in crystal growth apparatus

A method of producing a crystalline material comprising:

• providing a crystal growth apparatus comprising a chamber, and a hot zone within the chamber, the hot zone comprising at least one heating element, at least one heat removal system, a crucible containing at least solid feedstock, and a muffle surrounding the crucible, wherein the muffle is thicker in each of a plurality of corners thereof than in each of a plurality of sides thereof;
• orientating the muffle such that at least one corner of the plurality of corners of the muffle is positioned between a center of one side of the crucible and the heating element;
• heating the solid feedstock in the crucible with the heating system to form a liquid feedstock melt;
• uniformly applying heat from the heat zone to the feedstock from top to bottom through the muffle to control the temperature uniformity being applied to the solid feedstock;
• and
• cooling the heated feedstock to produce a crystalline material.