The dependence of the single-crystalline yield during physical vapor transport (PVT) growth of SiC on the thermal field was investigated systematically. It is shown that the development of a flat faceted growth interface improves crystal quality but restrains enlargement of the single-crystalline part in the grown SiC boules. A highly convex interface shape allows effective enlargement but leads to the generation of many defects. Modifications of the growth process were made to separately control the thermal field at the periphery of the growing SiC boules and in the central area. With proper tailoring of the radial temperature gradient, an enlargement of the single-crystalline part from 35 to 50 mm in diameter was achieved.