Large diameter silicon carbide bulk crystals were demonstrated recently. However, these were not necessarily high quality crystals because of excessive thermal stresses. We tried to make the radial temperature distribution uniform using tantalum cylinder and cone as a thermal reflector in order to decrease excessive thermal stresses in the growing bulk. As a result, the flat top bulk crystals were obtained. Diameter expansion and quality of SiC were due to the radial temperature gradient. When the temperature profile and radial temperature gradient were not optimized, many cracks were generated in the crystal.