Growth of High-quality Large Cubic Gem Diamond Crystals

Under high pressure and high temperature(HPHT),the diamond crystals often show hexoctahedral shape because of the growing region of the cubic {100} surface of a single crystal is very narrow.The diamond crystals were controlled to grow at a relatively low temperature,which is suitable for growth of {100} surface by temperature gradient method(TGM) under HPHT,with self-made Fe-Ni alloy solvent assisted,through adjusting the process of assembling and synthesis appropriately.All the crystals were synthesized to show complete morphology of cubic hexahedron.At the same time,the radial crystal growth rate and inhibited its axial growth rate were improved to inhibit inclusions and other impurities into the crystal.Within 33 h,high-quality hexahedral cubic crystals can be synthesized.The size of the longest dimension is 7.3 mm and the weight is 1.2 carat.Its radial growth rate achieves 0.22 mm/h,axial growth rate is only 0.08 mm/h,and the weight growth rate could increased to 7.3 mg/h.