Synthesis of Polycrystalline Diamond Compact with Selenium: Discovery of a New Se–C Compound

Sintering of polycrystalline diamond with selenium was investigated under pressure of 6.5–10.5 GPa at a constant temperature of 1850 ^\circ\!C. A new carbon-selenium compound with a most plausible chemical formula of SeC and a WC-type hexagonal structure (space group P\bar6m2) has been discovered in the recovered samples sintered at 10.5 GPa and 1850 ^\circ\!C. Refined lattice parameters are as follows: a = 2.9277(4) Å, c = 2.8620(4) Å, V = 21.245(4) Å^3. The diamond compacts hot-pressed at 10.5 GPa have excellent mechanical properties with a Vickers hardness of about 68 GPa at a loading force of 19.6 N. Diamond intergrowths observed in these samples may have benefited from the catalytic effects of Se/SeC on the nucleation and crystal growth of diamond.