HPHT Synthesis of Different Shape Coarse-Grain Diamond Single Crystals

Synthesis of coarse-grain diamond crystals is studied in a China-type SPD6×1670T cubic high-pressure apparatus with high exact control system. To synthesize high quality coarse-grain diamond crystals, advanced indirect heat assembly, powder catalyst technology and optimized synthesis craft are used. At last, three kinds of coarsegrain diamond (about 0.85 mm) single crystals with hexahedron, hex-octahedron and octahedron are synthesized successfully under HPHT (about 5.4 GPa, 1300–1450°C). The growth characters of different shape crystals are discussed. The results and techniques might be useful for the production of coarse-grain diamonds.